bacteriacells Types of cells Prokaryote - no organelles Eukaryotes - organelles animal cells plant cells
Animal cell Bacterial cell Cell size comparison most bacteria • 1-10 microns eukaryotic cells • 10-100 microns • micron = micrometer = 1/1,000,000 meter • diameter of human hair = ~20 microns
Why are cells so small? What limits cell size? Analogy: What limits the size of a human (hypothetical)? Why can’t we grow to be 10,000 pounds? You need around 15 calories per pound to maintain your body weight each day. Therefore, if you weigh 100 lbs, you would need to eat how many calories to maintain your weight each day? 1500 calories What if you weighed 1000 lbs? 15000 calories…
What limits cell size? Why is the weight record only around 1600 lbs? Carol Yager (1960-1994) This person needed to eat 24,000 calories a day…at some point you need to just constantly eat and take in immense amount of oxygen to support that volume and constantly get rid of waste!! Any more and you just can’t physically ingest and respire (take in O2 and breathe out CO2)excrete that much!
What limits cell size? • The logistics of carrying out cellular metabolism sets limits on the size of cells • The cell membrane is the site of ingestion/excretion of the cell • As the cell gets larger the cell membrane gets larger • What is the problem with this?
CALCULATING SA:V RATIOS TO EXPLAIN WHY CELLS ARE SO SMALL Now lets increase the volume 27X. 4. What is the new volume? 5. What surface area would the cell need? 600um2 x 27 = _________um2 Imagine a cell with the shape of a cube to keep it simple with the length of the sides = 10um. 1. Calculate the Volume (l*w*h) 2. Surface Area (l*w*# of sides) 3. SA:V ratio (simplified) 6. Calculate the new Surface Area and SA:V ratio. Is that enough surface? ______um2 _______um2 27X bigger ______um3 ________um3 ___um2 : ___um3 _____um2 : _____um3 This tells us that there is ___um2 of cell membrane for ____um3 of cell volume. That is not enough!! Cell can’t get what it needs and get rid of waste fast enough. This tells us that ____um2 of cell membrane is needed to feed and get rid of waste for ____um3 of cell volume.
CALCULATING SA:V RATIOS TO EXPLAIN WHY CELLS ARE SO SMALL Now lets increase the volume 27X. 4. What is the new volume? 5. What surface area would the cell need? 16,200 600um2 x 27 = _________um2 Imagine a cell with the shape of a cube to keep it simple with the length of the sides = 10um. 1. Calculate the Volume (l*w*h) 2. Surface Area (l*w*# of sides) 3. SA:V ratio (simplified) 6. Calculate the new Surface Area and SA:V ratio. Is that enough surface? 600 5,400 ______um2 _______um2 Only gets 9X bigger 27X bigger 1,000 27,000 ______um3 ________um3 ___um2 : ___um3 1 1.7 1 5 _____um2 : _____um3 This tells us that there is ___um2 of cell membrane for ____um3 of cell volume. That is not enough!! Cell can’t get what it needs and get rid of waste fast enough. 1 This tells us that ____um2 of cell membrane is needed to feed and get rid of waste for ____um3 of cell volume. 1 5 1.7
Surface area increases while total volume remains constant 5 1 1 Total surface area (height width number of sides number of boxes) 6 150 750 Total volume (height width length number of boxes) 125 125 1 Surface-to-volume ratio (surface area volume) 6 12 6 What limits cell size? The cell membrane will get larger as the cell gets larger…so what’s the problem? A smaller cell • Has a higher surface to volume ratio, which facilitates the exchange of materials into and out of the cell The problem is that the cell membrane does not increase proportionally with the volume or…if you double the volume, the membrane doesn’t double! Figure 6.7
All cells have basic features in common • Jobs: • make proteins • make energy • make more cells • Structures: • Plasma membrane • Cytosol • Chromosomes • Ribosomes
Prokaryotic Cells • Domains: Archea & Eubacteria • Kingdom: Monera • Size: 1 um-10 um • Simpler than eukaryotic cells • Do not contain a nucleus • Have their DNA located in a region called the nucleoid
Prokaryotic Cells Prokaryotic Ribosomes (similar to eukaryotic ribosomes) Semifluid (equivalent to cytosol of eukaryotes) DNA (prokaryotes have a single circular chromosome – piece of DNA found in the so called “nucleoid region”)
Prokaryotic Cells Capsule 1. Certain species only, pathogenic 2. Sticky polysaccharide coating 3. Protective Cell Wall 1. Composed of peptidoglycan It is a polysaccharide with peptides sticking off. • Pili • certain species only, pathogenic ones • Think of them like “velcro”…it allows bacterium to stick to surfaces. Plasma membrane (double black line)
Prokaryotic Cells Flagella is used for motility (movement). Different species have different numbers of flagella… Flagella
Pili: attachment structures on the surface of some prokaryotes Nucleoid: region where the cell’s DNA is located (not enclosed by a membrane) Ribosomes: organelles that synthesize proteins Plasma membrane: membrane enclosing the cytoplasm Cell wall: rigid structure outside the plasma membrane Capsule: jelly-like outer coating of many prokaryotes Bacterialchromosome 0.5 µm Flagella: locomotion organelles of some bacteria (a) A typical rod-shaped bacterium (b) A thin section through the bacterium Bacillus coagulans (TEM) Prokaryotic Summary
Flagella Bacterial flagella rotate in a circle (like a corkscrew) causing the bacterium to move through solution spiraling like a football. http://www.youtube.com/watch?v=2P9hvlsF9_c
Eukaryotic Cells • Domain: Eukarya • Kingdoms: Protista, Fungi, Plantea, Animalia • Contain a true nucleus, bounded by a membranous nuclear envelope • Are generally quite a bit bigger than prokaryotic cells • Internal membranes which form organelles
Golgi mitochondria chloroplast ER Why organelles? • Specialized structures • specialized functions • cilia or flagella for locomotion • Containers • partition cell into compartments • create different local environments • separate pH, or concentration of materials • distinct & incompatible functions • lysosome & its digestive enzymes • Membranes as sites for chemical reactions • unique combinations of lipids & proteins • embedded enzymes & reaction centers • chloroplasts & mitochondria
phosphate“head” Cell membrane • Function • separates cell from outside • controls what enters or leaves cell • O2, CO2, food, H2O, nutrients, waste • recognizes signals from other cells • allows communication between cells • Structure • double layer of fat • phospholipid bilayer • receptor molecules • proteins that receive signals lipid “tail”
The Protein Assembly Line Golgiapparatus ribosome ER Building Proteins • Organelles involved • nucleus • ribosomes • endoplasmic reticulum (ER) • Golgi apparatus • vesicles nucleus vesicles
Nucleus • Function • protects DNA • Proteins pack DNA into chromosomes • Structure • Nuclear lamina • Network of proteins on underside of nuclear envelope giving it shape and strength • Nuclear envelope • double membrane • membrane fused in spots to create pores • allows large macromolecules to pass through
nuclear membrane DNA mRNA Nucleus small ribosomal subunit nuclear pore mRNA large ribosomal subunit cytoplasm 1 production of mRNA from DNA in nucleus by RNA polymerase 2 mRNA travels from nucleus to ribosome in cytoplasm through nuclear pore
large subunit small subunit ribosome Nucleolus • Function • ribosome production • build ribosome subunits from rRNA & proteins • exit through nuclear pores to cytoplasm & combine to form functional ribosomes rRNA & proteins nucleolus
Ribosomes: Protein Factories in the Cell • Are particles made of ribosomal RNA and protein • Free floating vs. bound mRNA (copy of a gene) (Enlarged) ribosomes The ribosomes are in the cytosol locked out of the nucleus randomly diffusing around...
The Ribosome Carries out protein synthesis 3’ A U C G G C CGC A U U A C U G G C U 5’ C G C A U A Direction it reads From 5’ to 3’ mRNA
Types of Ribosomes • Freeribosomes • suspended in cytosol • synthesize proteins that function in cytosol • Bound ribosomes • attached to endoplasmic reticulum • synthesize proteins for export or for membranes membrane proteins
Endoplasmic Reticulum • Function • processes proteins • manufactures membranes (part of the endomembrane system) • synthesis & hydrolysis of many compounds • Structure • membrane connected to nuclear envelope & extends throughout cell
Types of ER rough smooth
Smooth ER function • Membrane production • Many metabolic processes • Stores calcium in muscle cells • Stores glucose as glycogen • In liver • synthesize lipids • oils, phospholipids, steroids & sex hormones • detoxify drugs & poisons • in liver • ex. alcohol & barbiturates
Membrane Factory • Build new membrane • synthesize phospholipids • builds membranes • ER membrane expands • bud off & transfer to other parts of cell that need membranes
Rough ER function • Produce proteins for export out of cell • protein secreting cells • packaged into transport vesicles for export
Vesicle Transport (a liposome) Vesicle membrane Membrane protein Filled with proteins Proteins in here and in vesicle membrane ER membrane Cytosol Membrane protein Inside ER Transport vesicle forming…
Vesicles in the News! • http://www.nytimes.com/2013/10/08/health/3-win-joint-nobel-prize-in-medicine.html?_r=1& • Video : http://online.wsj.com/article/SB10001424052702303442004579120823331406810.html
secretory vesicles transport vesicles Golgi Apparatus • Function • Receives transport vesicles from RER • Modification of products of ER • ships products in vesicles • membrane sacs
Vesicle fusion with plasma membrane Transport vesicle arrives at (PM) Inside Cell PM Outside Cell
- Membrane fusion proteins will fuse the membrane of the transport vesicle to the plasma membrane… Inside Cell PM Outside Cell
- Vesicle fusion occurs… - Notice that the proteins inside the vesicle are now outside the cell. And the proteins stuck in the vesicle membrane will now be in the plasma membrane… Inside Cell PM Outside Cell
- Soluble protein released - Plasma membrane protein in place - Also notice that new membrane (new phospholipids and cholesterol) have been added to the PM Inside Cell PM Fig. 4.10 Outside Cell
Plasma membrane proteins How did these proteins get embedded in the membrane?
nucleus cell membrane nuclear pore protein secreted rough ER vesicle ribosome proteins smooth ER transport vesicle Golgi apparatus cytoplasm Putting it together… Making proteins