BY1101 Introduction to Molecular and Cellular Biology

BY1101 Introduction to Molecular and Cellular Biology

Tutorial for module BY1101:

Cells & organellesJoe Colgan ([email protected])

http://www.phschool.com/science/biology_place/biocoach/cells/review.html


• Define and describe major cell groups• Examine organelles and their functions• Examine mechanisms of transport in and out

of the cell

Tutorial objectives

http://www.phschool.com/science/biology_place/biocoach/cells/review.html


What is a cell?Basic structural or functional unit of an organism

Which cell is which and why?

Prokaryotic cell Eukaryotic cell(Plant)

Eukaryotic cell(Animal)


Prokaryotic cell Which organisms have prokaryotic cells?

Prokaryotes: Bacteria and Archaea

Fimbriae/pili

Flagella

Plasma membrane

Cell wall

Capsule

Ribosome

Nucleoid

Chromosome


Name the organelles responsible for each of the following functions:

Prokaryotic cell – organelles functions

Function Organelle

FlagellaPropels the cell

Appendages that allow a bacterium to stick to a surface

Frimbriae/pili

Rigid structure that surrounds, supports, and protects the cell

Cell wall

Acts as a selective barrier, allowing passage of oxygen, nutrients, and wastes

Plasma membrane

Site of protein synthesisContains the genes that control the cell

Ribosome

Nucleoid


Animal Eukaryotic cellFlagellum

Nuclear envelopeNucleolusChromatin

Nucleus

Plasma membrane

Rough endoplasmicreticulum

Ribosomes

Golgi apparatus

Mitochondrion

LysosomeCentrioles

Peroxisome

Microvilli

MicrofilamentsInterm. filamentsMicrotubules

Cytoskeleton

Smooth endoplasmicreticulum


Plant eukaryotic cellNuclear envelopeNucleolusChromatin

Nucleus Rough endoplasmicreticulum

Smooth endoplasmicreticulum

Ribosomes

Central vacuole

MicrofilamentsInterm. filamentsMicrotubules

Cytoskeleton

ChloroplastPlasmodesmataCell wall

Plasma membrane

Peroxisome

Mitochondrion

Golgi apparatus


Eukaryotic cell – organelles functions

1. Cell support and movement

2. Synthesis of secretory proteins and membranes

3. Lipid synthesis, detoxification, and calcium storage

4. Modifies, stores, and repackages products of the ER, mostly for secretion

5. Protein synthesis

6. Support the cytoplasm

7. Carries out cellular respiration

8. Selective barrier, allowing passage of oxygen, nutrients, and wastes

9. Break down toxins in the cell-detoxify

10. Stores the cell's DNA and coordinates the cell's activities

11. Serves as tracks along which other organelles can move

12. Processes and packages proteins after their synthesis

Cytoskeleton/Microfilaments

Rough endoplasmic reticulum

Smooth endoplasmic reticulum

Golgi apparatus

Ribosomes

Cytoskeleton

Mitochondrion

Plasma membrane

Peroxisome

Nucleus

Microtubules

Golgi apparatus

Name the cellular structures responsible for each of the following functions:


PLANT Eukaryotic cell – organelles functions

a. Connect the cytoplasmic fluid of one cell to neighbouring plant cells

b. Storage, waste disposal, protection and growth

c. Carries out photosynthesis / where chlorophyll traps solar energy

d. Maintain cell shape and protects from mechanical stress

Name the 4 structures that are only present in plant eukaryotic cells?

Match the function to the correspondent structure:

Plasmodesmata

Chloroplast

Central vacuole

Chloroplast

Plasmodesmata

Central vacuole

Cell wall

Cell wall


ANIMAL Eukaryotic cell – organelles functionsName the 2 structures that are only present in animal eukaryotic cells?


a. Important in breaking down food and recycling

b. Compression girders of the cytoskeleton Centrioles

Lysosome

Lysosome

Centrioles


Tour of the cell

Nucleus


Function: The “brains” of the cell. The nucleus directs cell activities and contains genetic material called chromosomes made of DNA. Storage, replication and transcription of DNA.

1. Allows ribosomal subunits and mRNA transcribed off genes in the DNA to leave the nucleus, enter the cytoplasm, and participate in protein synthesis

2. Involved in the assembly of ribosomal subunits

3. Separates nucleus from the cytoplasm

4. DNA and proteins that make up the chromosomes

Nucleolus

Nuclear envelope

Nuclear pores

Chromatin



What is the function of the ribosomes?Function: Main sites of protein synthesis

Appear in two cytoplasmic locales (i.e. Locations)

Free ribosomesSuspended in the cytosol

Bound ribosomesBound to nuclear envelope or endoplasmic reticulum

Proteins remain in the cytosol

Proteins inserted in membranes, packed into specialised organelles or

exported (secreted)

Ribosomes

Endoplasmic reticulum (ER)


Smooth ERPortion of the ER free of ribosomes

Roles: Synthesis of lipids

Drug detoxificationCalcium storage

Rough ERPortion of ER studded with ribosomes

Roles:Site of secretory proteins

Membrane proteins

What are the two sections?

Rough ER

Ribosomes

Nucleus

LumenCisternaeSmooth ER

Function: Biosynthesis of a number of macromolecules


Golgi apparatusWhat is the function of the golgi apparatus?

Function: Processes and packages proteins after their synthesis


LysosomeWhat is the function of the lysosome?

Function: Degradation of host and foreign macromolecules into individual monomers


1. A secretory protein is synthesized inside the RER and migrates through it, and exits inside a vesicle

2. The transport vesicle moves through the cytoplasm to the Golgi apparatus

RER

Golgi apparatus

Endomembrane

RER

Golgi apparatus

3. The Golgi modifies the protein as it moves from cis face to trans face

4. The protein is dispatched from the Golgi in a transport vesicle that then fuses with the plasma membrane, releasing the protein to the outside of the cell


Endomembrane


What are the powerhouses of the cell?

Mitochondria


Function: Conversion of oxygen and nutrients into adenosine triphosphate (ATP)

Chloroplast


•Chloroplast contains thylakoid vesicles•Thylakoid vesicles are stacked together to form structures known as grana • Thylakoids contain chlorophyll and are the site of photosynthesis• Soluble matter (stroma) fixes carbon dioxide


Extracellular matrix

Extracellular matrix

Glycolipid

Carbohydrate

Glycoprotein

CytoskeletonCholesterol

Protein

Phospholipids

Plasma membraneFunction: Selective barrier, allowing passage of oxygen, nutrients, and wastes


Selective permeability

1. Hydrophobic interior of the bilayer2. Hydrophobic molecules (soluble in

lipids) can move through3. Certain molecules, such as hydrophilic

molecules or ions, move slowly through or cannot pass at all.

How do they get through?


Transport proteins

Specific membrane transport proteins in the plasma membrane form a channel through which water molecules of a specific solute can pass


Transport across the membraneWhat are the two types of transport

Passive transport Active transport


Diffusion

What is diffusion? Tendency for particles of any kind to move from where they are more concentrated to less concentrated

Molecules are also said to move along their concentration gradient. What is the concentration gradient? A region along which the density of a chemical substance increases or decreases


Facilitated diffusion

What is facilitated diffusion? Spontaneous passage of molecules and ions, bound to specific transport proteins, across a biological membrane down their concentration gradients


Active transport

Active transport – Requires ATP input1. Cells need to expel sodium and intake

potassium2. Sodium ions bind to the transport protein.3. ATP transfers a phosphate group that

changes the shape of the protein, the sodium ions are pushed across the membrane and released


Active transport

4. Potassium ions now bind to the protein and the phosphate group is released.

5. The release of the phosphate group causes the protein to revert to its original shape, releasing the potassium ions into the cell. The process can be repeated.


2 types of exocytosis

Requires a sorting signal (clathrin coat) and an increase in intracellular calcium


3 types of endocytosis – uptake material into cell

“Cellular drinking”Dissolved in waterInvagination

Large particlesCell changes shapee.g. bacteria

Small particlesReceptor-ligand interactione.g. Metabolism of cholesterol


Exam 2010

Past paper questions


Questions([email protected])

Further reading: Campbell

Chapter 6: Tour of the cellChapter 7: Membrane structure and function

BY1101 Introduction to Molecular and Cellular Biology

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