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AP Bio Unit 2: Cell Structure and Function
Surface Area
outside area of an object |
the area around the outside of a cell |
unit: m^2 |
Application in Living Things
increased 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 Phospholipid
hydrophilic head: |
hydrophobic tail: |
phosphate |
saturated fatty acid |
glycerol |
unsaturated fatty acid |
cholesterol
at warm temperatures: |
at cool temperature: |
restrains the movement of phospholipids and reduces fluidity |
maintains fluidity by preventing tight packing |
Passive Transport
no energy |
high to low concentration |
diffusion |
osmosis |
facilitated diffusion |
ion channels |
Diffusion
passive transport |
molecules spread out to available spaces |
move down concentration gradient (high to low concentration) |
work to reach equilibrium |
Active Transport
no 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 |
Prokaryotic vs. Eukaryotic Cells
similarities: 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 |
Plant Cells in Pure Water
pure 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 |
Osmoregulation
organisms without cell walls that live in hypertonic or hypotonic environment must have adaptations for osmoregulation |
the control of water balance |
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Volume
amount of space inside of the object |
the space inside of the cell |
unit: cm^3 |
Fluid Mosaic Model
phospholipids: provides fluidity and elasticity |
proteins and other molecules embedded in membrane |
Phospholipid Bilayer
amphipathic |
hydrophilic heads |
hydrophobic tails |
Proteins
integral proteins: |
peripheral proteins: |
imbedded through the membrane (inside) |
on hydrophilic portion of the cell membrane (outside) |
Carbohydrates
cell 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 Theory
an 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) |
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Surface Area to Volume Ratio
a 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 Membrane
two main components: |
other important molecules: |
phospholipids |
cholesterol |
proteins |
carbohydrates |
Functions of Membrane Proteins
intercellular joinings |
enzymatic activity |
transport (active/passive) |
cell to cell recognition |
anchorage/attachment |
signal transduction |
Cell Membranes are Semipermeable
properties 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 Potential
the 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 Cell
Plant Cell: |
Animal Cell: |
chloroplast |
cilia and flagella |
central vacuole |
centrioles |
cell wall |
lysosomes |
The Endomembrane System
a 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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