4. Cell Structure and Function
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Transcript of 4. Cell Structure and Function
Cell Biology
Cells
• Cell – Smallest unit of life that can function independently
– Discovered by Robert Hooke – 1660
– Antony van Leeuwenhoek – improved lenses, made observing cells easier
• Cell Theory – Schleiden, Schwann
– All organisms are made of one or two cells
– Cell fundamental unit of all life
Surface Area/Volume
History of Cell Biology
Robert Hooke 1635-1703
History of Cell Biology
Anton von Leeuwenhoek 1673-1723
Leeuwenhoek Microscope(circa late 1600s)
History of Cell Biology
Cell Theory: 1800s
Theodor Schwann Matthias Schleiden
Microscopes
• Microscope uses an energy source (light, electrons, ect.) to view objects under magnification– Can view things that you cannon view with the naked eye– Light Microscopes – uses light to view things in real color,
item must be thin enough to get light thru.• Compound – uses 2 or more lenses to focus visible light through
a specimen, magnify 1600 times• Confocal – focus white or laser light through a lens to the
object.
– Electron Microscopes – MUCH higher magnification• Transmission – Sends beam of electrons through a sample• Scanning – Sends beam of electrons over the surface of object
Microscopy
Why do we need microscopes?
Resolution
Resolution: ability to distinguish two points as distinct
Picture created and printed at a high resolution
Picture created and printed at a low resolution
Microscopy
Light MicroscopyADV: living cells
DISADV: low resolution
Light Microscopy
Phase Contrast
Light Microscopy
Differential Interference Contrast
Electron Microscopy
Uses beams of electrons
Electron Microscopy
Scanning Electron Microscopy (SEM)ADV: shows details of cell surfaces
Electron Microscopy
Transmission Electron Microscopy (TEM)
Cell Structures
• All cells have these structures:
– DNA
– RNA
– Ribosomes – make proteins
– Proteins
– Cytoplasm – fluid filling of the cell
– Cell Membrane – makes a boundary between inside and outside of cell
Types of Cells – Prokaryotic
• Lack a true nucleus and membrane bound organelles
• Domains Bacteria and Archaea
• Structures:– Nucleoid – contains cells DNA, NOT bound by a
membrane
– Cell Wall – rigid, outside of cell membrane, gives cell its shape (rod-shaped, round, spiral)
– Flagella – whip-like tail for movement
Types of Cells - Eukaryotic
• All other cells except for bacteria, archaea
– Plants, animals, protists, fungi
• Domain – Eukarya
• Have MEMBRANE BOUND organelles, larger than prokaryotic
• 2 basic types of eukaryotic cells
– Animal
– Plant
Cell Membrane
• Function: – Separate cell from environment– Transport substances in and out of cell– Receive and respond to stimuli
• Properties– Hydrophobic and hydrophilic– Selectively permeable
• Structure:– Phospholipid bi-layer– Fluid mosaic of phospholipids, sterols, proteins
• Transport Proteins
• Enzymes
• Recognition Proteins
• Adhesion Proteins
• Receptor Proteins
Proteins
Animal cell membrane
• Cell wall
– Maintain structure
– Maintain internal pressure
Nucleus
• Function:– “Brain” of the cell
– Contains DNA, mRNA
• Structure– Nucleolus – assemble ribosomes
– Nuclear envelope – separates nucleus from cytoplasm
– Nuclear pores – holes in envelop with channels for mRNA to leave nucleus
Nucleus
Nuclear envelope
Nucleolus
Nuclear pore
1) Nuclear envelope2) Outer ring3) Spokes4) Plug
Nucleus
Endoplasmic Reticulum and Ribosomes
• Rough Endoplasmic Reticulum (ER)– Function: Help make cell membrane and secretory
proteins for various bodily functions• In pancreas, insulin; leukocytes, antibodies
– Structure: Connected to nuclear envelop and cell membrane with ribosomes on outside
• Smooth ER– Function: Make and store proteins, carbohydrates, lipids
• In liver, enzymes for detox; muscle, proteins for contraction
– Structure: Same as smooth ER – ribosomes
• Ribosomes– Function: Assemble proteins for the cell– Structure: Large and small subunits
The Endomembrane System
Rough Endoplasmic Reticulum: makes secreted and
membrane proteins, and proteins destined for some organelles
The Endomembrane System
Smooth Endoplasmic Reticulum: synthesizes lipids,
steroids, detoxifies
The Endomembrane System: Endoplasmic reticulum
Rough ER
The Endomembrane System: Endoplasmic reticulum
Golgi Apparatus
• Function:
– Process and complete protein production
– Sorts and packages proteins to send to cell membrane and out or as membrane proteins
• Structure:
– Stack of flat membrane enclosed sacs
The Endomembrane System: Golgi
Receives vesicles from RER and packages proteins for export
The Endomembrane System: Golgi
Receives vesicles from RER and packages proteins for export
Lysosomes
• Function: – Digestion
– Enzymes to break down and recycle food, bacteria, old organelles
• Structure:– Made by Golgi Apparatus
– Fuse with vesicles that have things that need to be digested
• Number of lysosomes depends on type of cell– White blood cells, liver cells - lots
The Endomembrane System: Lysosomes
Membranous sac of digestive enzymes
Vacuoles
• Function:– Same as lysosomes
– Replace lysosomes in plant cells
– Growth
– Maintain pressure
– Holds pigments
– Contractile vacuole – protists (pump water, digest)
• Structure:– Contains water solution of enzymes, sugars, salts,
weak acids
The Endomembrane System: Vacuoles
• Various Functions http://www.youtube.com/watch?v=iG6Dd3COug4
Contractile vacuole
Central vacuole
Peroxisomes
• Function:
– Dispose of toxic substances
– Protect cells from toxic byproducts
• Structure:
– DIFFERENT from lysosomes that originate from ER NOT Golgi body
Peroxisomes
Peroxisomes (green)
Cytoskeleton
• Function: – Transportation within the cell– Support– Cell division– Connectivity– Movement – Cilia and flagella
• Structure:– Network of protein tubules and tracks
• Microfilaments• Intermediate filaments• Microtubules – organized by centrosomes
The Cytoskeleton and Cell Surfaces
Microfilaments
Functions
(1) Structure
(2) Cell motility (muscles)
The Cytoskeleton and Cell Surfaces
Intermediate Filaments
Functions:
(1) Cell shape
(2) Anchor organelles
Keratin intermediate filaments (red)
The Cytoskeleton and Cell Surfaces
Microtubules
Functions:
(1) Support
(2) Tracks
(3) Cell division
The Cytoskeleton and Cell Surfaces: Cilia and Flagella
http://www.youtube.com/watch?v=QGAm6hMysTA
http://www.youtube.com/watch?v=7kM_kRPrcrkhttp://www.youtube.com/watch?v=09kLIsNfaO8&NR=1
Cilia
The Cytoskeleton and Cell Surfaces: Cilia and Flagella
Structure:
9+2
Basal body
Dynein
Spokes
Extracellular Matrix
Glycoproteins: proteins + carbohydrates, fibers
Extracellular Matrix
Glycoproteins: proteins + carbohydrates, fibers
C-terminally truncated human glypican-1
Endosymbiotic Theory
Chloroplast
• Function:– Site of photosynthesis
– Only 1 type of plastid – all have different pigments
• Structure– Double membrane
– Stroma – inner fluid
– Thylakoid – stacked disks with grana• Have photosynthetic pigments (chlorophyll)
– Have OWN DNA and ribosomes
Plastid
Chloroplast
Mitochondria
• Function:– Powerhouse of the cell
– Carries out cellular respiration
• Structure:– Double membrane
– Matrix – inner “goo”
– Crtistae – folds in inner membrane w/ enzymes for cellular respiration
– Have OWN DNA
Cell Junctions
Type Function Example Location
plasmodesmata enable direct, regulated, symplastic intercellular transport of substances between cells
plant cell walls
tight junctions hold cells together; help to maintain the polarity of cells; prevent the passage of molecules and ions through the space between plasma membranes of adjacent cells
the kidney and liver
anchoring (adhering) juctions
serve as a bridge connecting the actin cytoskeleton of neighboring cells through direct interaction
epithelial and endothelial tissues
gap junctions connects the cytoplasm of two cells, which allows various molecules, ions, and electrical impluses to directly pass through a regulated gate between cells
nerves
Cell Junctions: Tight Junction
Cell Junctions: Anchoring (Adhering) Junction
Cell Junctions: Gap Junction
Organelles Summary
Organelle Structure FunctionPlantCells?
Animal Cells?
Nucleus contains DNA and RNA provides a segregated site for genetic transcription, allowing levels of gene regulation that are not available to prokaryotes
Yes Yes
Ribosome highly complex; made up of dozens of distinct proteins
serves as the primary site of biological protein synthesis (translation)
Yes Yes
Rough endoplasmic reticulum
membrane studded with ribosomes manufacture of secreted proteins; manufacture of lysosomal enzymes
Yes Yes
Smooth endoplasmic reticulum
membrane (smooth) synthesizes lipids, phospholipids, and steroids Yes Yes
Golgi apparatus large stacks of membrane-bound structures
packages proteins inside the cell before they are sent to their destination
Yes Yes
Lysosome spherical vesicles containing enzymes break down proteins, nucleic acids, carbohydrates, lipids, and cellular debris
Rarely Yes
Central vacuole enclosed compartments filled with water isolates materials that might be harmful or a threat to the cell; contains waste products
Yes No
Peroxisome lipid bilayer membrane; crystalloid core (not always present)
breakdown very long chain fatty acids; detoxify various toxic substances that enter the blood
Yes Yes
Chloroplast outer and inner membrane surrounding thylakoid system
conduct photosynthesis Yes No
Mitochondrion Membrane surrounding cristae and matrix (containing mitochondrial DNA)
generate most of the cell's supply of ATP, used as a source of chemical energy
Yes Yes
Cytoskeleton network of fibers composed of proteins; dynamic
allows cells to migrate; stabilizes tissues Yes Yes
Cell wall tough, flexible layer surrounding cells protection and filtering Yes No