Chapter 3: Cell Biology & Genetics 1/17/12 12:35 PM

Intro

Most of earth’s cells are unicellular

Most ancient cells are bacteria

3 main types of microscopes

o Light

o Transmission Electron

o Scanning Electron

Cell Theory :

o New cells are formed from other existing cells, and that the

cell is a fundamental unit of structure, function, and

organization in all living organisms

Cellular Activity is both individual and collective

o Dictated by sub-cellular structures

Continuity of life has cellular basis

Humans are composed of 70 trillion cells

Cellular Diversity:

Not all cells look alike

Don’t perform identical roles

70 trillion cells in the human body

260 different types of cells

vary in size & shape

size/shape determined by the proteins made

Cell differentiation is how cells become other cells

Types of Cells:

Stem Cells: have the ability to renew themselves through mitotic

cell division and differentiate into a diverse range of specialized cell

types; can replicate indefinitely

o Embryonic Stem Cells: Can become any type of cell

(totipotent);

o Adult stem cells are found in breast tissue & umbilical cord

blood

Progenitor Cells: partly specialized daughter cells of stem cells

o Commited cells/ specific type of cell

o Can divide a limited number of times

o Repair system for the body- replenish special cells, but also

maintain the blood, skin & intestinal tissues

Cell Aging:

Wear & tear theory : chemical insults, free radicals (cumulative

effects)

Genetic theory : cessation of mitosis, pre-programmed genes

(apoptosis)

All cells of the body contain the same DNA

Embryos exposed to chemical signals that hinder development

Genes of specific cells turn on or off

Cell Characteristics: mini protein factories

Smallest part of an organism

Plasma (cell membrane): forms outer boundary of the cell through

which cell interacts with its external environment

Nucleus: centrally located; directs cell activities (mostly take place

in cytoplasm); genetic library; dictates the kind & amount of

proteins to be made

Cytoplasm: located between the plasma membrane and the

nucleus. 80% water

Organelles: perform specific functions

o Mitochondria : power plant of cell; aerobic respiration

Functions of the Cell

Cell Metabolism & Energy use:

o chemical reactions are metabolic reactions (cell metabolism)

o energy released from reactions is used for cellular activities

(synthesis of molecules & muscle contraction); other energy

released is used for heat to maintain body temp

Synthesis of Molecules:

o Cell makes diff types of molecules (proteins, nucleic acids,

and lipids)

o Functions of cells determined by type of molecules produced

Communication:

o Cells produce/respond to chem and electrical signals (allow

them to communicate to one another)

Nerve cells produce chem signals which allows

communication with muscle cells (respond by

contracting or relaxing)

Reproduction & Inheritance

o Cells contain complete copy of all genetic info of individual

(determines structural & functional characteristics of cell)

o During growth, cells divide to produce new cells (with same

genetic info)

o Gametes (specialized cells of the body) are responsible for

transmitting genetic information to the next generation

Plasma Membrane

Lipid bilayer (phospholipids & cholesterol) with proteins embedded

in either surface

Function: Controls entry & exit of substances; receptor molecules

function in intercellular communication; marker molecules enable

cells to recognize one another

Selectively Permeable :

o Some materials freely pass (small hydrophobic molecules,

CO2 AND O2, and small lipids, and small polar molecules

(H20)

o Some materials are excluded (large molecules)

o Some materials enter or leave the cell only by the using cell

energy/protein channels (Ions and nutrient molecules)

Cytosol (fluid part)

Water w/ dissolved ions & molecules; colloid with suspended

proteins (catalyze decomposition & synthesis reactions)

Cytoskeleton (internal skeleton)

o Composed of microtubules (large), intermediate filaments,

microfilaments (small- centrioles, cilia/flagella, basal bodies)

o Support cytoplasm (anchors organelles/maintains shape) &

form centrioles, spindle fibers, cilia, & flagella

o Responsible for movement of structures in cell

Actin filaments/Microfilaments (smallest)

Composed of actin (protein); spider web like

Provide structure to cytoplasm

Mechanical support to microvilli

Support plasma membrane & define shape of cell

(reconstruct to help cells move)

Responsible for muscle’s contractile capabilities

Cyclosis: movement of cytoplasm contents within

the cell

“Amoeboid” movement and phagocytosis

Mitosis : cleavage furrow in cytokinesis

Intermediate filaments

Composed of keratin (protein)

Mechanical strength to cells

Cell Attachments

Microtubules (largest)

Hollow; composed of tubulin (protein)

Support & structure to cytoplasm

Help transport intracellular materials

Form key parts of centrioles, spindle fibers, cilia,

and flagella

Mitosis: Form the spindle apparatus (separates

chromosomes during cell division)

Cytoplasmic Inclusions

o Stored nutrients, secretory products, and pigment granules

o Function depends on molecules

Energy storage (lipids, glycogen)

Oxygen transport (hemoglobin)

Skin color (melanin)

Pigments that incr with age (lipochromes)

Nucleus: contains/stores DNA; determines how cell will function & basic

structure of cell; manufactures all RNA; duplicates DNA b/f cell division;

largest organelle;

Nuclear Envelope

o Double membrane

o Nuclear pores that contain RNA and protein that provide

channels for exchanging substances with the cytoplasm of the

cell

Proteins lining pores determine which molecules

enter/leave the nucleus

o Outer surface coated with ribosomes

o Endoplasmic reticulum is connected to the nuclear envelope

Chromatin

o Combination of all DNA and histones in nucleus

o Threadlike strands of DNA used to form chromosomes

Condenses to form chromosomes during cell division

DNA and histones (protein important for structural

organization)

o Condenses into chromosomes (x) during mitosis

o After DNA replication, chromosomes have two chromatids

(one of the lines in the x)

DNA: blueprint for protein synthesis

o found in the cells nucleus

o Genes are the instruction carrying units of DNA

o DNA combines with RNA to make a protein

o Chromosomes condensed nuclear DNA and proteins

(histones); consists of two chromatids

o Chromatids : attached at centromeres

Kinetochore: protein structure in centromere; provides

point of attachment for microtubules during cell division

o Establishes structure of protein by specifying the sequence of

their amino acids

o Ribonucleic acid (RNA) : intermediate for DNA that can leave

the nucleus

DNA determines structure of messenger RNA (mRNA),

ribosomal RNA (rRNA), and transfer RNA (tRNA)

o Gene: sequence of nucleoties in a DNA molecule that specifies

the structure of a protein or RNA molecule

Nucleolus

o Small concentrated masses DNA, RNA, and protein

o Synthesis of ribosome subunits

Ribosomes are the site for protein synthesis

Ribosomes have 2 subunits (large/small) & are

composed of RNA & protein

Ribosomal subunits move into cytoplasm for functioning

(attached to rough ER or free in cytoplasm)

Free ribosomes: synthesize proteins used inside the cell

Ribosomes attached to endoplasmic reticulum produce

proteins that are secreted from the cell

Cytoplasmic Organelles: structures within cells specialized for particular

functions; secretion of proteins = ER & Golgi

Rough Endoplasmic Reticulum: synthesizes, transports, and

isolates intracellular contents

o Membranous tubules and flattened sacs with attached

ribosomes

o Connected to nuclear envelope

o Protein synthesis: produced and modified for secretion

o Vesicles formed at ER migrate to the Golgi bodies, merge &

pass through the Golgi & are packaged and labeled for export

in Golgi vesicles

Smooth Endoplasmic Reticulum

o Membranous tubules and flattened sacs with no attached

ribosomes

o Abundant in cells that produce many lipids

o Make lipids and carbs and steroids via enzymes

o Stores calcium trigger muscle contraction

o Detoxifies harmful chemicals (alcohol)

o Increases surface area for action/storage of enzymes

Golgi Apparatus: secrete large amounts of protein (glycoproteins),

such as cells in the salivary glands & the pancreas

o Composed of stacks of cisternae (isolated from cytoplasm)

o Processing center for materials to be packaged up &

distributed in organelles or exported/secreted from the cell in

vesicles pinched off of the tips of the Golgi membranes

Digestive enzymes packaged for lysosomes

Hormones are packaged into vesicles for secretions

o Modifies packages (protein & lipid packaging) made by the

rough/smooth ER before export

Carb portion of glycoproteins are added in the Golgi

body

Polysaccharides are made in the Golgi

o Proteins become more concentrated and chemically altered

o Distributes protein & lipids for secretion of internal use

Vesicular transport model : vesicle (forms membrane of

ER) moves to the Golgi apparatus, fuses with its

membrane, & releases the protein into its cisterna; The

Golgi concentrates/chemically modifies the proteins by

making/attaching carb molecules to proteins to form

glycoproteins or by attaching lipids to proteins to form

lipoproteins; proteins are then packaged into vesicles

that pinch off from the margins of the Golgi and are

distributed

Some vesicles carry proteins to the plasma

membrane, where proteins are secreted from the

cell by exocytosis

Other vesicles contain proteins that become part

of the plasma membrane

Other vesicles contain enzymes that are used

within the cell

Secretory Vesicle

o Membrane-bound sac pinched off Golgi apparatus

o Carries protein and lipids to cell surface for secretion

(membranes fuse w/ plasma membrane & released by

exocytosis; membranes of vesicles then are incorporated into

plasma membrane)

Lysosome (vesicles)

o Contains enzymes that can breakdown carbs, proteins, nucleic

acids, & many lipids (intracellular digestive system)

o Made from enzymes/membranes of the rough ER and

packaged in the Golgi (pinched off)

o Contains digestive enzymes; digest pathogens & destroy

nonfunctional organelles (cell maintenance & renewal);

Autophagia: process where lysosomes digest

organelles of cell that aren’t functional

o Lysosomes move to plasma membrane & enzymes are

secreted by exocytosis

(ex) bone remodeling: breakdown of bone tissue by

specialized bone cells; enzymes responsible for that

degradation & are released into extracellular fluid from

lysosomes produced by those cells

Peroxisome

o Smaller than lysosomes

o Detoxify and neutralize/break down free radicals by

transferring hydrogen in reactions to oxygen (peroxide –

H202) via the enzyme catalase

Breaks down hydrogen peroxide into water & oxygen

o Detoxification for liver & kidney cells (many peroxisomes)

o One site of lipid and amino acid degradation

Proteasomes

o Large protein complexes (recycle proteins within the cell)

o NOT surrounded by membranes

o Tubelike protein complexes in the cytoplasm

o Destroy unneeded, damaged or faulty proteins

Mitochondria: provide energy for the cell (ATP production)

o Spherical rod-shaped, or threadlike structures

o Enclosed by double membrane

o Inner membrane forms cristae (projections)

Enzymes found in cristae: enzymes of citric acid cycle

(inner membrane) & of electron transport chain (matrix)

o Major site of ATP synthesis when Oxygen is available

Contains enzymes needed to get energy from the carbs.

That energy forms ATP

o The larger the energy requirements of the cell, the more

mitochondria

o Contain their own DNA and ribosomes & can self-replicate

Not as many strands of nuclear DNA as nucleus

Does not have histone associated proteins

Centrioles (microtubules)

o Pair of cylindrical organelles in the centrosome

Centrosome: specialized zone of cytoplasm close to

the nucleus & is the center of microtubule formation

Contains 2 centrioles

o Consists of triplets of parallel microtubules

Microtubules: influence distribution of actin &

intermediate filaments

Extend from centrosomes

o Centers for microtubule formation

o Determine cell polarity during division in mitosis

o Form the basal bodies of cilia and flagella

o Determine cell shape & movement

Spindle Fibers (microtubules)

o Microtubules extending from centrosome to chromosomes &

other parts of the cell (ex) aster fibers

o Assist in the separation of chromosomes during cell division

Cilia

o Project from surface of cells

o Move small particles across the cell

o Move materials across cell surfaces

Movement of microtubules past each other (requires

ATP) responsible for movement of cilia

Dynein arms: proteins connecting adjacent pairs of

microtubules (push microtubules past each other)

Basal body (modified centriole) located in cytoplasm at

base of cilium

o Formed from microtubules

o Small in length; many in a cell

Numerous on surface cells that line the respitory tract

and the femal reproductive tract

Cilia in the trachea move mucus w/ dust particles away

from the lungs (keeps lungs clear of debris)

Flagellum

o Tail-like projection used to propel the cell

o Responsible for movement of sperm cells (entire cell)

Only human cells with flagella (only 1 per cell)

o Long length & a cell has very few

Microvilli

o Extension of plasma membrane containing microfilaments

o Increase surface area of the plasma membrane for absorption

& secretion

o Modified to form sensory receptors

Elongated microvilli in hair cells of inner ear respond to

sound

o Smallest (smaller than cilia

o No movement

o Supported with actin filaments (not microtubules)

o Found in intestine, kidney, & other area in which absorption is

important

Fluid Mosaic Model of Plasma Membrane

Bilayer of phospholipids & cholesterol with proteins “floating” in the

membrane

Nonpolar/hydrophobic region of each phospholipid molecule is

directed toward the center of the membrane

o Phospholipid heads

Polar/hydrophilic region is directed toward the water environment

either outside or inside the cell

o Phospholipid tails

Proteins In the Plasma Membrane

Marker Molecules: intercellular communication

o Allow cells to identify one another or other molecules

o Glycoproteins

o Cadherins : proteins that attach cells to other cells

o Integrins : proteins that attach cells to extracellular molecules

Attachment Proteins : Intracellular Joining

o Anchor cells to other cells (cadherins) or to extracellular

molecules (integrins)

Transport proteins : carriers

o Channel Proteins

Form passageways through the plasma membrane

(allowing specific ions or molecules to enter/exit the

cell)

May be gates or nongated

o Carrier Proteins (transporters)

Move ions/molecules across the membrane

Binding of specific chemical to carrier proteins causes

changes in the shape of the carrier proteins (requires

ATP- active transport)

The carrier proteins then move the specific chemical

across the membrane

o ATP- powered pumps : transport proteins

Move specific ions or molecules across the membrane

Require ATP molecules to function

Receptor Proteins: Recognition

o Function as binding sites for chemical signals in the

extracellular fluid (guide cell attachments/adhesions)

o Exposed receptor site which attaches to specific chemical

signals

o Binding of chemical signals to receptors triggers cellular

responses

o Immune system: distinguish foreign cells

Enzymes

o Catalyze chemical reactions either inside or outside cells

Passive Transport: moving biochemical and atomic or molecular

substances across the cell membrane

Osmosis: movement of water across a partially permable

membrane from an area of low solute concentration to an area of

high solute concentration. It is a physical process in which solvent

moves, without input of energy, across a semipermeable membrane

(permeable to the solvent, but not the solute) separating two

solutions of different concentrations. (water follows “stuff”)

Simple Diffusion: H20, CO2, O2, & small lipid-solubles (alcohol)

o net movement of substances from a region of high

concentration to a region of low concentration

o Substances are diffused across the membrane between the

phospholipids.

o Rate of diffusion is slow & can’t cover much distance

Facilitated Diffusion: the spontaneous passage of molecules/ions

across a biological membrane passing through specific

transmembrane transport proteins

o Glucose, many small ions, amino acids

Filtration: movement of solute molecules and water across a

membrane by normal cardiovascular pressure. The size of

membrane pores dictate the molecule that may pass

Active Transport: some transport proteins (carrier proteins) use energy to

move molecules against the concentration gradient

Requires two carrier protein active sites

o One to recognize the substance to be carried

o One to release ATP to provide the energy for the protein

carriers or “pumps”

Concentration gradients of ions (H or Na ions)

o used to provide energy

Exocytosis: moves substances (solid particles) out of a cell

Endocytosis: moves substances in a cell

Phagocytosis : “cell eating”; larger vesicles formed; solid particles

ingested (bacteria, cell debris & foreign particles); eliminates

harmful substances from the body (white blood cells

phagotyze)

Pinocytosis : “cell drinking”; smaller vesicles are formed; engulfs

molecules dissolved in liquid (not particles) engulfs extracellular

fluid

Transcytosis : substances are drawn into, across and out of a cell (in

one side, out the other side). Common for pathogens (viruses)

Vesicular Transport: moves large particles across a membrane

REVIEW

Intracellular: inside the cell

Extracellular: outside the cell

Intercellular: between cells

Plasma Membrane potential: charge difference across the plasma membrane

(outside is positive & inside negative)- polarized; caused by regulation of ion

movement by cells; Sodium ions & Postassium ions

Sodium Ions are responsible for making the outside of the cell

Large proteins inside the cells are responsible for net negative

Glycocalyx: collection of glycolipids, glycoproteins, & carbs on outer surface

of plasma membrane; contains molecules absorbed from extracellular

environment

Function of Cholesterol in plasma membrane

1/3 of total lipids in plasma membrane

regulates fluidity and permeability

Cholesterol limits the movement of phospholipids, providing

stability to plasma membrane

Integral vs peripheral proteins in the plasma membrane

Integral: passing through the width of the membrane; acts as

transport channels

Peripheral: acts as recognition sites; contains carbs to help cell

recognition

o Glycolipid: lipids attached to carbs; blood type (antigens)

o Glycoproteins: proteins attached to carbs; blood type

Two Functions of marker molecules

Intracellular communication- glycoproteins

Recognition (no foreign objects enter cell)

Three Types of cell communication

Contact Signaling: cell touching via sugar chains

Electrical signaling: via “ion gates”

Chemical signaling: via neurotransmitters & hormone

G-protein receptors: via second messenger

Cadherins vs Integrins: cell adhesion and cellular communication

Cadherins: proteins that attach cells to other cells; homophilic

o Epithelial, placental, neural

Integrins: proteins that attach cells to extracellular molecules;

heterophilic; function in pairs of integral proteins which interact with

intracellular & extracellular molecules

Three Classes of Transport Proteins

Channel Proteins

Carrier Proteins

ATP powered pumps

Nongated ion channels: channel protein; always open; permeability to ions

Ligand-gated ion channels: channel protein; open or close in response to

chemical signals (small molecules that bind to the proteins/glycoproteins)

Voltage gated ion channels: channel protein; open/close when there is a

change in charge across the plasma membrane

Uniport: movement of one specific ion or molecule across membrane

Symport: movement of two different ions or molecules in the same direction

across plasma membrane

Antiport: movement of two diff ions or molecules in opposite directions

across the plasma membrane

Carrier Proteins (transporters) move ions/molecules from one side of plasma

membrane to the other by using specific binding sites at which

ions/molecules attach & the protein changes shape to move the bound ions

to the other side of plasma membrane where they are released.

Facilitated diffusion (doesn’t require energy- moves from

higher concentration gradient to a lower one) – passive

transport

ATP Powered Pumps : movement of ions or molecules across the membrane

is fueled by the breakdown of ATP. There are binding sites for the protein &

binding site for ATP. The breakdown of ATP into ADP releases energy which

changes the shape of the protein to move ion across membrane

Active transport

Receptor molecule: chemical signal attaches to receptors on the cell surface.

When chemical signals (ligands) bind to the receptors, the channels either

open or close

Changes permeability because receptors offer a selectively

permeable interface

o the receptors check for a ligand (structure on entering

molecule that has a structure complementary to its own)

o if the appropriate ligand is present, the molecule gains entry

into the cell

Receptors alter activity of G protein complexes

G proteins on inner surface of plasma membrane & acts as

intermediate between a receptor and other cellular proteins

Alpha, Beta, & Gamma proteins

G protein complex only associates with a receptor that has a

chemical signal bound to it

Activated (alpha) subunits stimulate cell response in 3 ways:

o Intracellular chemical signals

o Opening of ion channels in the plasma membrane

o Activation of enzymes associated with the plasma membrane

Action of enzyme in the cell membrane

Breaks the peptide bond of a dipeptide to produce 2 amino acids for

enzymes on the surface of cells

MOVEMENT THROUGH THE PLASMA MEMBRANE

Molecules/ions Can Pass Through Plasma Membrane in 4 Ways:

Directly through the phospholipid membrane

o Molecules that are soluble in lipids (O, CO2, steroids) dissolve

in lipid bilayer

o Bilayer is a barrier to substances that are not lipid-soluble

Membrane Channels

o Protein channels for size, shape, & charge

o Rapid movement of water across cell membrane

Transport Proteins

o Large polar molecules (not lipid soluble)- glucose & amino

acids

o Transported by mediated processes

o Specific molecules bind to specific transport proteins that

carry them across plasma membrane

Vesicles

o Large nonlipid-soluble molecules, small pieces of matter &

whole cells

o Membranous sacs involved in transport

o Vesicle & plasma membrane fuse because of fluid nature of

membranes, allowing contents of vesicle to cross plasma

membrane

Diffusion: movement of solutes from an area of higher solute

conecentration to an area of lower solute concentration

Concentration gradient: the concentration difference between two

points, divided by the distance between two points

o Solutes diffuse down concentration gradients (from higher to

lower solute concentration) until equilibrium is achieved

o Decreasing concentration difference or increasing distance

between 2 points lower concentration gradient

Rate of diffusion influenced by:

o Temperature (Higher temperature, faster molecule

movement)

o Molecule size (smaller molecules move more easily)

o Concentration (Initial rate faster with higher concentration)

o Viscosity of the solvent (Diffusion rate decreases with more

viscous solvents)

Osmosis: diffusion of water (solvent) across a selectively permeable

membrane (allows water, but not all solutes to enter)

Aquaporins: water channel proteins

o Increase membrane permeability to water in kidney cells

Water diffuses from less concentrated solution (fewer solutes, more

water) into more concentrated solution (more solutes, less water)

Importance: large volume changes caused by water movement

disrupt normal cell function

Osmotic Pressure : force to move water through membrane; -

osmotic refers to concentration of the solutions

o The greater the concentration of a solution, the greater the

osmotic pressure of the solution & the greater the tendency

for water to move into the solution

o Isosmotic : solutions with same concentration of solute have

the same osmotic pressure

o Hyperosmotic : more concentrated solution with higher

osmotic pressure

o Hyposmotic: The more dilute solution with lower osmotic

pressure

-tonic refers to tendency of cells to swell/shrink

o Isotonic : osmotically balanced (tonicity); equal proportions of

solutes to water on both sides of the membrane; artificially

made to resemble body fluid (Gatorade)

o Hypertonic : water moves out of cell by osmosis causing cell to

shrink (crenation); solution is hypertonic because solution

has a higher solute concentration (less water) than the cell

(ex) food preservation

o Hypotonic : water moves into cell by osmosis, causing the cell

to swell (lysis); solution is hypotonic because it has a lower

solute concentration (more water) than the cell (ex) distilled

water

Filtration: process of separating suspended particles from the fluid through a

porous material in which the fluid can pass while the suspended particles are

retained

Depends on pressure difference on either side of the divider

o Liquid moves from greater pressure to lower pressure

Occurs in kidneys as a step in urine formation

Occurs when blood pressure moves fluid from the blood (water,

ions, and small molecules pass through, but most proteins and

blood cells remain in the blood)

Mediated Transport

Process by which transport proteins (carrier, ATP-powered pumps,

and channel proteins) assist in the movement of large, water-

soluble molecules or electrically charged molecules/ions across the

plasma membrane (ex) amino acids and glucose & proteins

Characteristics

o Specificity: each transport protein binds to and transports

only a single type of molecule or ion; determined by the

chemical structure of the binding site

For Channel protein (ion channels), specificity is

determined by size and charge within a channel

o Competition: similar molecules binding to the transport

protein; the substance in the greater concentration or that

binds more readily is passed through membrane

o Saturation: the rate of movement of molecules across the

membrane is limited by the number of available transport

proteins; occurs when all carrier proteins/channels are

occupied

As concentration of a transported substance increases,

more transport proteins have their binding sites

occupied (maximum rate)

Rate of transport :

o As the concentration differences increase, the rate of

transport increases and then levels off

When concentration of molecules outside cell is low,

the transport rate decreases

More molecules outside the cell more molecules

being transported/ transport rate increases (if transport

proteins are available)

When the number of molecules outside the cell

outnumbers the transport proteins, the system is

saturated & transport rate cannot increase.

Three Kinds :

o Facilitated Diffusion: carrier/channel mediated; moves

substances in & out of cells from a higher to lower

concentration; rate of transport is directly proportional to their

concentration gradient up to the point of saturation, then the

rate of transport is constant at its max rate

o Active Transport: requires energy provided by ATP to move

substances against concentration gradients (low to high); rate

depends on number of pumps & availability of ATP;

Sodium-potassium pump : moves Na out of cells and K

into cells; ATP is broken down

o Secondary active transport: does not require ATP

molecule; gets energy from existing concentration gradient

(sodium); one molec moves out of cell with the energy from

other molecule moving in the cell

Glucose is moved from the lumen of the intestine into

epithelial cells by this process

Endocytosis & Exocytosis

Endocytosis: internalization of substances (phagocytosis &

pinocytosis)

o Uptake of material through the plasma membrane by the

formation of a vesicle (membrane-bound sac found within the

cytoplasm of a cell)

o Receptor-mediated endocytosis: specific molecules are

ingested into the cell, as a result of a receptor-ligand

interaction; specificity & saturation

Increases rate at which substances enter cell

Cholesterol and growth factors are molecules accepted

by the receptor

Exocytosis : substances contained in vesicles are discharged from

cell

o (ex) secretion of digestive enzymes by the pancreas and

secretion of mucus by the salivary glands

Cytoplasm: half cytosol and half organelles

Cytosol : fluid portion, cytoskeleton, and cytoplasmic inclusions

o Fluid portion = dissolved ions and molecules and a colloid

with suspended molecules (proteins, which catalyze

breakdown of molecules for energy)

o Cytoskeleton=

supports cell & holds the nucleus/other organelles in

place

responsible for cell movements

three groups of proteins: microtubules, actin filaments &

intermediate filaments

Genes & Gene Expression

Heredity : genetic transmission of characteristics (traits) from

parents to their offspring

Genes : functional units of heredity; responsible for the

characteristics of cells (inherited- traits of the entire organism)

o Each gene is a segment of a DNA molecule

DNA molecules (w/ proteins) form chromosomes

o Gene: All the triplets necessary to make functional RNA

molecule or protein

o 2 types of Genes

Structural: DNA sequences that determine specific

amino acid sequences in proteins (enzymes, hormones,

or structural proteins like collagen)

Regulatory : segment of DNA involved in controlling

which structural genes are expressed in a given tissue

Sequence of nucleotides in a DNA molecule is a method of storing

information that is based on a triplet code

o Triplets: Three consecutive nucleotides that form the words of

the triplet code

Used to construct other DNA molecules, RNA molecules,

& proteins

Gene Expression : production of proteins (made in the cytoplasm)

from the info stored in DNA; region of a DNA molecule between the

promoter & terminator

o 2 Steps

Transcription: copy DNA from genes (DNA stays in

nucleus)

mRNA = copy of DNA that travels from the

nucleus to ribosomes in the cytoplasm

Translation: converting copied information into a protein

Information in the copy (mRNA) constructs protein

Amino acids are key to making proteins

o Transfer RNA (tRNA) : specialized transport molecules that

carry amino acids to the ribosomes

2 Sections of protein-coding regions of RNA

o exons: code for parts of a protein & sections

o Introns: do not code for parts of a protein

Transcription

o Synthesis fo mRNA, tRNA, and rRNA based on the nucleotide

sequence in DNA

o Occurs when a section of a DNA molecule unwinds and its

complementary strands separate

One of the DNA strands is the template strand for

transcription (DNA transcribed into RNA)

Nucleotides that form RNA align with the DNA

nucleotiedes in the template strand by complementary

base pairing

Thymine (from DNA) with Adenine

Adenine with a Thymine (from DNA)

Cytosine with a Guanine (from DNA)

Guanine with a Cytosine (from DNA)

Uracil (from RNA) with Adenine (from DNA)

RNA polymerase : enzyme that makes the complementary RNA

molecule from DNA

o Attaches to a DNA nucleotide sequence (promoter)

To attach: RNA polymerase associates with transcription

factors (other proteins) so that it can interact with DNA

o Attachment of polymerase to promoter causes a portion of

DNA to unwind (exposing nucleotide sequence)

Complementary RNA nucletides then align with DNA

nucleotides of the template strand

RNA nucleotides combined by dehydration reactions

(catalyzed by RNA polymerase) to form mRNA

o RNA polymerase detaches from DNA (releasing the new form

of mRNA) when it encounters a terminator (DNA nucleotide

sequence)

Genetic Code: information contained in mRNA

Codons: sets of three nucleotide units which carries genetic code

o Specifies an amino acid during translation

o Start codon: signals beginning of translation

o Stop codon: signals end of translation

Do not specify amino acids

Translation: synthesis of a protein at the ribosome in response to the codons

of mRNA

Requires ribosomes and tRNA

o Ribosomes consist of ribosomal RNA (rRNA) and proteins

mRNA, tRNA, and rRNA are produced in the nucleus by

transcription

o tRNA: matches specific amino acid to a specific codon of

mRNA

one end of each kind of Trna COMBINES WITH A

SPECIFIC AMINO ACID

anticodon : consists of three nucleotides and is

complementary to a particular codon of mRNA; only can

combine with its matched codon

REVIEW

1. Difference between Start Codon & Promoter and between Stop Codon &

Termination Site?

The start codon is located on the mRNA strand (it signals

TRANSLATION to start by recruiting the large ribosomal unit to the

small one). The promoter is located on the DNA strand (it signals

TRANSCRIPTION to start).

The stop codon is located on the mRNA strand (it signals

TRANSLATION to stop, via the Release Factor). The termination

sequence is located on the DNA strand (it signals TRANSCRIPTION to

stop)

2. Where are codons and anticodons found and how is their relationship

crucial to protein synthesis?

Codons are the mRNA triplets of nucleotides (i.e. AUG, CUG, etc)

that are made by DNA (transcription). DNA is in the nucleus and

makes a strand of mRNA. This mRNA leaves the nucleus and goes

out into the cytoplasm and binds to a ribosome. These mRNA

codons are complementary to triplets of nucleotides in a tRNA

molecule (anticodon) which is out in the cytoplasm of the cell. This

tRNA anticodon brings the amino acid that it codes for into the

ribosome (translation) to join with other amino acids to eventually

become a protein.

These relationships - DNA to mRNA (transcription) and mRNA with

tRNA (translation) are what direct the process of protein sythesis.

The base pairing of the nucleotides from a DNA codon to a mRNA

codon and from mRNA to a tRNA anticodon are what determine the

sequence of amino acids in the protein.

3. Describe the role of mRNA, rRNA, and tRNA in the production of a protein

at a ribosome. What is a polyribosome?

mRNA carries genetic information copied from DNA in the form of a

series of three-base code “words” which specifies a particular amino

acid

tRNA is the key to deciphering the code words in mRNA. Each type

of amino acid has its own type of tRNA, which binds it and carries it

to the growing end of a polypeptide chain if the next code word on

mRNA calls for it. The coorect tRNA with its attached amino acid is

selected at each step because each specific tRNA molecule contains

a 3 base sequence that can base-pair with its complementary code

word in the mRNA

rRNA associates with a set of proteins to form ribosomes. These

complex structures (physically move along an mRNA molecule)

catalyze the assembly of amino acids into protein chains. They also

bind tRNAs and various accessory molecules necessary for protein

synthesis. Ribosomes are composed of a large & small subunit,

each of which contains its own rRNA molecule or molecules

Translation is the whole process by which the base sequence of an

mRNA Is used to order and to join the amino acids in a protein.

4. What are Exons & Introns? How do they related to Post-Transcriptional

RNA processing and mrNA?

Prokaryotic DNA transcription produces messenger RNA, which is

necessary for transfer from the cell nucleus to the cytoplasm where

translation occurs. In contrast, eukaryotic DNA transcription takes

place in a cell's nucleus and produces what is called a primary RNA

transcript or pre-messenger RNA. Before eukaryotic products of

transcription can be moved into the cytoplasm, they must undergo

modifications that allow them to become mature messenger RNA.

Splicing is the name given to the reaction that removes

unnecessary segments of the primary RNA transcript, called introns.

The removal of the introns produces mRNA (see the figure, below).

Messenger RNA contains only exons, those portions of the primary

RNA transcript that will be translated into a protein.

5. Relationship among centrosomes, spindle fibers and kinetochores of

chromosomes during cell division?

CELL LIFE CYCLE: changes a cell undergoes from the time it is formed until

it divides to produce two new cells

2 stages:

o Interphase : phase between cell division; 90% or more of life

cycle

cell carries out metabolic activities

performs specialized functions (ex) secretion digestive

enzymes

cell prepares to divide

increase in cell size (b/c many cell components

double in quantity)

replication of the cell’s DNA: 2 new strands of DNA

are made (using two existing strands as

templates)

replication of the centrioles within the centrosome

Three Subphases

G1, S, and G2

G1 (gap phase)- cell carries out routine

metabolic activities

S (synthesis phase)- DNA is replicated

G2 (second gap phase)- cell prepares for

cell division

G0 phase: resting cells exit cell cycle

o Cell Division stage

Division of the nucleus to form two new nuclei

Division of the cytoplasm to form 2 new cells

Each of the new cells contains one of the newly

formed nuclei

division of nucleus occurs by mitosis

division of cytoplasm is cytokinesis

Mitosis:

Division of nucleus into two nuclei (each with same amount and

type of DNA as original nucleus)

DNA (replicated during interphase) is dispersed as chromatin

o Chromatin becomes very densely coiled to form compact

chromosomes (each chromosome consists of two chromatids

attached at the centromere)

Each chromatid contains a DNA molecule

As daughter cells are formed, chromatids separate and

are now called a chromosome

4 phases:

o Prophase

o Metaphase

o Anaphase:

Cytokinesis begins; formation of a cleave furrow

(indentation of the plasma membrane-forms midway

between centrioles); actin filaments pull plasma

membrane inward, dividing cell into halves

o Telophase

Genetics: study of heredity

Mendelian Genetics : study of how certain genetic traits are passed

from parent to offspring (used to determine risk of disease

inheritance)

o During the production of gametes (sex cells), each gamete

receives one hereditable factor

o Genotype : genes an organism has for a given trait

o Phenotype : expression of the genes as traits

o Genes (alleles) occur in dominant and recessive forms

Dominant : mask effects of recessive allele for a trait

Human genome : all of the genes in a human chromosome

Modern Use of Genetics

Chromosomes

o Made up of DNA and proteins found in the nuclei of somatic

cells(all cells of the body except for the gametes)- (ex)

epithelial cells, muscle cells, neurons, fibroblasts,

lymphocytes, and macrophages

Diploid: # of chromosomes in somatic cell; humans=46

Humans have 23 paired chromsomes

Haploid : # of chromosomes in a gamete

Haploid number of chromosomes is 23

o Gametes

Males sperm cells

Females oocytes

o Autosomal Chromosomes: all chromosomes but sex

chromosome (22 pairs)

o Sex Chromosomes: determine sex of individual (1 pair)

Female = XX in each somatic cell

Male = XY in each somatic cell

o Karyotype: display of chromosomes of a somatic cell during

metaphase of mitosis

Homologous: chromosome pairs

Genome: all the genes found in the haploid number of

chromosomes from one parent

Combined genomes from parents responsible for

all genetic traits

Multiple Alleles: dominant and recessive

o 2 alleles for each given gene (one on each homologous

chromosome)

o differences in alleles caused by mutation (DNA nucleotide

sequence is altered)

Gene Dominance

o Complete dominance: homozygous dominant and herozygote

had the same phenotype

o Codominance: two allesles at the same locus are expressed so

that separate, distinguishable phenotypes occur at the same

type

(ex) ABO blood types

o Incomplete Dominance: dominant allele does not completely

mask the effects of the recessive allele in the heterozygote

Heterozygote produces less of the protein product than

the homozygous dominant & has intermediate

phenotypic characteristics

(ex) beta thalassemia: disorder of a gene on

chromosome 11 (affects synthesis of beta globulin

polypeptide chains- which are part of hemoglobin in red

blood cells)

hemoglobin=protein that transports oxygen

anemia: deficiency of hemoglobin in the blood

blood transfusions key to maintain

hemoglobin levels

Polygenic Traits

o Many genes determine phenotype

o (ex) height, intelligence, eye color, skin color

Sex Linked Traits

o Traits affected by genes on the sex chromosomes

X linked traits = on x chromosome

Y linked traits = on y chromosome

o Most are x-linked because y chromosome is very small

Hemophilia A ability to produce certain blood clotting

factors is not present

Clotting impaired & persistent bleeding

Meiosis and Transmission of Genes

Gametes are produced that have one homolog from each of the

homologous pairs of chromosomes

o Gametes have ½ the number of chromosomes and ½ the

alleles of the original diploid cells

Gametes are haploid cells that are derived from diploid

cells

o Punnett Square : probability of the transmission of alleles to

the next generation (if the genotypes of parents are known)

Carrier for a recessive trait is a person who is

heterozygous for that trait (one normal allele and one

disorder-causing allele)

Genetic Disorders

Failure of structure, function, or both as a result of abnormalities in

a person’s genetic makeup (his/her DNA)

Mutagens: agents that cause mutations

Nondisjunction: one of the daughter cells receives both

chromosomes and the other receives none

o Aneuploidy: 47 chromosomes vs 45 chromosomes in daughter

cells (instead of normal 46)

Downs Syndrome (trisomy 21): 3 chromosomes 21 are

present

Syndrome = set of signs and symptoms occurring

together as the result of a single cause (ex) single

mutation or one extra chromosome (a trisomy)

2 Purposes of Cell Division

body growth

tissue repair

Mitosis: process by which a cell separates the chromosomes in its cell

nucleus into two identical sets in two nuclei

4 Phases of Mitosis

Prophase

Metaphase

Anaphase

Telephase

Cytokinesis: division of cytoplasm

Control of Cell Division:

Surface to Volume Ratio

Chemical Signals

Growth Factors

Hormones

Contact

Inhibition

Some tissues lose the ability to divide

Hyperplasia: increased number of cell divisions (often a cause for abnormal

pap smears in women)

Diseases characterized by uncontrolled cell proliferation create tumors or

neoplasm

Cancerous Neoplasm (malignant tumor or malignancy) can turn into

metastasis which is the spread of a disease from one organ or part to

another non-adjacent organ or part.

Causes of Cancer

Carcinogens (chemicals)

Radiation

Viruses/Mutation (ex) HPV

Types of Cancer & location:

Carcinomas- epithelial cells

Melanomas- melanocytes (skin)

Sarcomas- muscle cells or connective tissues

Leukemia- blood forming organs (bone marrow)

Lymphoma- lymphatic tissue

Angiogenesis: formation of new blood vessels

triggered by cancer cells dividing rapidly and continuously

Carcinogenesis:

multistep process

involves mutation of oncogenes and anti-oncogenes

Many mutations may have to accumulate before it becomes cancer

Treatment of cancer is difficult because it is not a single disease

Cells in a tumor do not all behave the same way

Cancer treatments

Surgery

Chemotherapy

Radiation therapy

ATP Production

Glycolysis (in cytoplasm…glucose goes in)

Krebs Cycle (citric acid cycle)

Electron Transport Chain (in mitochondria…ATP comes out)

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Importance of Physics

Deals with matter, energy & interactions

Humans like to ask why?

We are curious & want to understand

Universe is mysterious

Importance of Units

Give meaning to the numbers we calculate

1 mi= 1609 m

Vectors vs Scalar

Vector: position, velocity, & acceleration & displacement

o Magnitude (size) & direction

o (ex) 5 meters to the right

o displacement is vector quantity

o velocity = m/s in direction

Scalars: speed, distance

o Only Magnitude (size of vector) or distance

Magnitude of velocity is speed

o (ex) 5 meters

o distance is scalar quantity

o speed = m/s (rate of motion/change in position)

o rate (speed)=distance/time

o can be positive or negative

Acceleration

Rate of change of velocity over time (changes velocity)

slope in velocity vs. time graph

o Slowing down if velocity and acceleration are opposite signs

o Speeding up if velocity and acceleration are the same signs

In position vs time graph, acceleration=0 when:

o there is a change in concavity and

o when velocity is constant

In position vs time graph, acceleration is speeding up if it’s concave

up & slowing down if concave down

Vector quantity

For constant acceleration: Δv/Δt= v(final)-v(initial)/ Δt

o m/s^2

o if doesn’t change=constant acceleration

Constant acceleration is like a compound interest

o space ship at launch: a lot of acceleration; sustains

acceleration for a short time b/c limited supply of energy &

fuel (dot-com portfolio)

o Balanced portfolio

Consistent returns sustained over a long period

Starts slow- but acceleration starts building

1. Which of the following is vector?

Velocity (specify number & units & direction): rate at which an

object changes position

Displacement

2. Which is scalar? (specify number & units)

Distance

Speed

3. Speed=distance/time interval

units: m/s

always positive

4. Velocity= displacement/time interval (Δx/Δt)

units: m/s or mph/s

can be negative/positive

at same speed= uniform speed; constant velocity

4 types of motion:

Linear: straight line

Circular: revolving

Rotational: spinning about itself

Projectile Motion: elliptical; 2 dimensional (up & down- basketball)

The Particle Model:

Numbers show order of frames

Single dot represents the object

Coordinate System:

Towards right (horizontal)= positive displacement along x axis

Towards left (horizontal) = negative displacement along x axis

Moving up (vertical) = positive displacement

Moving down (vertical) = negative displacement

Motion Diagram

Ball: at rest/stationary

Skateboard: constant speed (more same amount in each time

interval)

Girl: Speeding up

Car: Slowing Down

Basketball: move along 2 dimensional (vertical & horizontal)

o Vertical: distance shrinking going up (negative) or

accelerating going down (positive)

o Horizontal: constant speed

Displacement= final position – initial position

Direction matters

Vector

Can be negative

One dimensional

Position vs. Time Graph

Point: specifies position at a given instant of time

Path: between 2 points describing the motion

Slope: indicates speed or velocity (rise/run)

Direction: (slope) indicates direction of motion

Steeper slope = faster speed

o Positive slope = moving in positive direction

o Negative slope = moving in negative direction

o If slope is decreasing, object is slowing down

o If slope is increasing, velocity is speeding up

X (final) = x (initial) + Velocity (x) Δt

o Position Equation for an object in uniform motion

(velocity of x is constant)

o Δx =v (x) Δt

Concave down: acceleration decreasing (neg)

Concave up: acceleration is increasing (positive)

Velocity vs. Time Graph

Displacement/distance = area under curve (m)

Acceleration = slope (change in velocity/change in time)

o Constant acceleration = constant slope (magnitude 0, horiz

line)

o Acceleration= change in distance/change in time

If sign for acceleration is same as sign for velocity, it is speeding up.

If different, it’s slowing down.

Uniform Motion

No acceleration

Motion with Acceleration