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AP Bio Unit 2: Cell Structure and Function
Surface Areaoutside area of an object | the area around the outside of a cell | unit: m^2 |
Application in Living Thingsincreased surface area = increased diffusion | microvilli: increases absorption in intestines | root hairs: increases water/nutrient absorption in plants | endomembrane system: increased folds in organelles allow for more surface area to do cellular work | cristae of the mitochondria: folds in the inner mitochondria increase amounts of ETC (more ATP) |
Structure of Phospholipidhydrophilic head: | hydrophobic tail: | phosphate | saturated fatty acid | glycerol | unsaturated fatty acid |
cholesterolat warm temperatures: | at cool temperature: | restrains the movement of phospholipids and reduces fluidity | maintains fluidity by preventing tight packing |
Passive Transportno energy | high to low concentration | diffusion | osmosis | facilitated diffusion | ion channels |
Diffusionpassive transport | molecules spread out to available spaces | move down concentration gradient (high to low concentration) | work to reach equilibrium |
Active Transportno energy | low to high concentration | sodium potassium pump: 3 sodium leave and 2 potassium enter cell against the concentration gradient | proton pump: hydrogen atoms pumped against concentration gradient | cotransport: H+ gradient helps to bring other molecules into cell | endocytosis and exocytosis |
Osmoregulationorganisms without cell walls that live in hypertonic or hypotonic environment must have adaptations for osmoregulation | the control of water balance |
Plant Cells in Pure Waterpure water (hypotonic solution) will initially move into the cells | after a period of time the cells will become turgid (swollen) | as turgor pressure increases, water will diffuse out of the cell... eventually equilibrium will be reached |
Prokaryotic vs. Eukaryotic Cellssimilarities: cell membrane, DNA, ribosomes, cytoplasm | | | Prokaryotes: | Eukaryotes: | organelles: | no nucleus | nucleus | | | no membrane bound organelles | membrane bound organelles | reproduction: | binary fission | mitosis and meiosis | average size: | smaller | larger | DNA: | DNA is circular | DNA is linear | | | single chromosome | paired chromosomes |
| | Volumeamount of space inside of the object | the space inside of the cell | unit: cm^3 |
Fluid Mosaic Modelphospholipids: provides fluidity and elasticity | proteins and other molecules embedded in membrane |
Phospholipid Bilayeramphipathic | hydrophilic heads | hydrophobic tails |
Proteinsintegral proteins: | peripheral proteins: | imbedded through the membrane (inside) | on hydrophilic portion of the cell membrane (outside) |
Carbohydratescell to cell recognition: | membrane carbohydrates: | cell's ability to distinguish one type of neighboring cell from another | interact with the surface molecules of other cells, facilitating cell to cell recognition |
Passive Transport (diffusion)the tendency for molecules of any substance to spread out into available space | substances will move down a concentration gradient | high to low concentration |
Passive Transport (osmosis)the diffusion of water | water moves from hypotonic to hypertonic | isotonic: equal solute across a membrane | hypotonic: less solute, more water | hypertonic: more solute, less water | low to high concentration |
Active Transport (endocytosis)cell takes in macromolecules by forming vesicles from plasma membrane | phagocytosis: "cellular eating," engulfing solids | pincytosis: "cellular drinking," engulfing solutes |
Active Transport (exocytosis)transport vesicles migrate to the membrane, fuse with it and release their contents |
Osmoregulation (paramecium)
The Endosymbiotic Theoryan evolutionary theory of the origin of eukaryotic cells from prokaryotic organisms | endosymbiosis: one organism living inside another | evidence 1) chloroplasts and mitochondria multiply in the same way as ancient bacteria | evidence 2) chloroplasts and mitochondria both control their own DNA and ribosomes | evidence 3) chloroplasts and mitochondria both have two membranes (inner membrane contains different proteins than the outer membrane) |
| | Surface Area to Volume Ratioa comparison between the size of the outside of an object and the amount inside | smaller cells have an increase SA:V | as the cell gets bigger, the SA:V decreases | small cells are more efficient at diffusion as they have a high ratio |
Structure of Cellular Membranetwo main components: | other important molecules: | phospholipids | cholesterol | proteins | carbohydrates |
Functions of Membrane Proteinsintercellular joinings | enzymatic activity | transport (active/passive) | cell to cell recognition | anchorage/attachment | signal transduction |
Cell Membranes are Semipermeableproperties of molecules that can get through the phospholipid bilayer: | properties of molecules that can not get through the phospholipid bilayer: | small | large | nonpolar | polar | nonionic | ionic | hydrophobic | hydrophilic | O2 and CO2 |
Passive Transport (facilitated diffusion)transport proteins allow molecules to flow from high to low concentration | aquaporins: tunnel that allows water to go through the membrane | glut: glucose transporter |
Passive Transport (ion channels)transport proteins allow ion to flow from a high to low concentration |
Passive and Active Transport
Water Potentialthe force responsible for movement of water in a system | solute potential: determined by solute concentration | pressure potential: results from exertion of pressure on membranes/walls as water moves in or out; can be positive or negative |
Plant vs. Animal CellPlant Cell: | Animal Cell: | chloroplast | cilia and flagella | central vacuole | centrioles | cell wall | lysosomes |
The Endomembrane Systema system of synthesizing proteins for export | 1) Nucleus: ~transcription (DNA -> RNA) ~make ribosomes | 2) Rough ER: ~translation (RNA -> proteins) ~proteins for export | 3) Vesicle: transports proteins in cells | 4) Golgi Apparatus: process and package proteins | 5) Vesicle: transports proteins in cells | 6) Cell Membrane: exocytosis |
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