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AP Biology: Unit 2 Cheat Sheet (DRAFT) by

Cell Structure and Function

This is a draft cheat sheet. It is a work in progress and is not finished yet.

Prokar­yotes vs. Eurkar­yotes

Simila­rities~
1. bound by plasma membrane
2. contains cytoplasm
3. contains chromo­somes
4. contains ribosomes
Differ­ences~
prokar­yotes
eukaryotes
- DNA in nucleoid
- DNA in nucleus
- no membra­ne-­bound organelles
- cytoplasm with membra­ne-­bound organelles
- smaller size
- larger size
- smaller ribosomes
- larger ribosomes
- circular DNA
- linear DNA

Surface Area

large S.A. to volume ratio to...
perform cellular metabolism more effici­ently & exchange materials with enviro­nment more effici­ently
as cell increases in volume and S.A. decrea­ses...
a higher demand of resources creates a limitation
microv­illi: long finger­-like projec­tions
increase S.A. (little change to volume)
compar­tme­nta­liz­ation =
metabolic processes can happen simult­ane­ously & enzymes built into membrane (for metabo­lism)

Plasma Membrane

- selective permea­bility: regulates the passage of substances across the membrane
- 'fluid mosaic': (1) phosph­olipid bilayer that shifts and moves (2) various proteins embedded
- phosph­olipids→ hydrop­hilic head (polar) & hydrop­hobic tail (nonpolar)
- choles­terol→ regulates fluidity of membrane as temp. changes ("fl­uidity buffer­")
- glycol­ipids→ membrane carboh­ydrates bonded to lipids
- glycop­roteins→ membrane carboh­ydrates bonded to proteins

Membrane Activity

CAN enter
CAN'T enter
small nonpolar molecules (gases)
ions
hydrop­hobic molecules
hydrop­hilic molecules (charged)
small polar molecules (water)
large polar molecules (glucose)

6 Membrane Protein Functions

- integral proteins: throughout the hydrop­hobic interior
- peripheral proteins: loosely bound to the surface of the membrane

Passive Transport Vocab

-passive transport:
diffusion of a substance with NO use of energy
-diffu­sion:
movement of a substance down its concen­tration gradient (HIGH to LOW)
-osmosis:
diffusion of water across a membrane (HIGH to LOW of water)
-facil­itated diffusion:
diffusion of a substance with the assistance of transport proteins
 
ex) K+ leaves the cell; water from aquaporins
-carrier protein:
a change in shape moves the substance across
-channel protein:
a channel which molecules pass through
-gated channels:
channels that open/close in response to stimulus
 
ex) electr­ical, binding of a substance, or pressure
-aquap­orin:
channel protein that facili­tates osmosis by passing a LOT of water

Tonicity

Active Transport Vocab

-active transport:
moving a substance across a membrane against the concen­tration gradient WITH energy (LOW to HIGH)
-sodium- potassium ion pump:
movement of Na+ out of the cell and K+ into the cell
-elect­rogenic pump:
generates a voltage across a membrane while pumping ions
 
ex) Na+/K+ pump (animals); proton pump (plants, bacteria, fungi)
-proton pump:
transport of H+ ions out of the cell
- sucrose/H+ cotran­sport:
movement of H+ into a cell down its gradient (taking sucrose w/ it) & then H+ transp­orted out of cell (proton pump)
-exocy­tosis:
secretion of a substance by the fusion of vesicles on the membrane
-endoc­ytosis:
1. phagoc­ytosis 2. pinocy­tosis 3. recept­or-­med­iated endocy­tosis
1. phagoc­ytosis
engulfing "­foo­d" or other particles
2. pinocy­tosis
engulfing extrac­ellular fluid molecules
3. recept­or-­med­iated endocy­tosis
engulfing bulk quantities of substances

Endosy­mbiont Theory

- mitoch­ondria and chloro­plast originated as prokar­yotic cells engulfed by a eukaryotic cell & evolved into a single organism
supporting evidence~
1. both have 2 membranes (when engulfed)
2. both contain ribosomes
3. both are autonomous (grow & reproduce on own)
4. both make own proteins
5. both have DNA

Water and Osmotic Potential

Y
s
(or Y
π
): due to molarity ---- negative value (higher M = more negative)
↳ determines the tonicity (hyper­tonic = high M/more - & hypotonic = low M/less -)
Y: tells the direction the water will go
Y
p
: 0 when exposed to open air
  

Endome­mbrane System

PARTS
ROLES
1. nuclear envelope
synthesize proteins
2. ER
transport proteins
3. golgi apparatus
metabolism (& movement of lipids)
4. lysosomes
detoxi­fic­ation
5. vesicl­es/­vac­uoles
  
6. plasma membrane
  

Ribosomes

- function: synthesize proteins from mRNA
(made from rRNA and proteins)
-free ribosomes: suspended in the cytosol (enzymes)
-bound ribosomes: attached to the ER/nuclear envelope (proteins for membranes; packaging w/in organe­lles; export from cell)

Nucleus

-nuclear envelope: double membrane enclosing the nucleus
-nuclear pores: holes in the nuclear envelope (regulate entry/exit of proteins and RNAs)
-chrom­osome: coiled up DNA
-chrom­atin: mass of uncoiled DNA
nucleolus: center of the nucleus respon­sible for rRNA synthesis & assembling subunits for ribosomes

Golgi Apparatus

(made of flattened membra­ne-­bound sacs -- cisternae)
-function: modifies proteins and sends them to destin­ation & makes some macrom­ole­cules

Endopl­asmic Reticulum

-rough ER: (ribosomes attached) packages proteins synthe­sized from ribosomes
- smooth ER: (NO ribosomes) detoxi­fic­ation & lipid synthesis

Lysosome

(sacs that contain hydrolytic enzymes)
- function: digest materials (w/ enzymes) & recycle intrac­ellular materials

Vacuole

- food vacuole: engulf (phago­cyt­osis) materials as food for the cell
- contra­ctile vacuole: moves excess water out of the cell
- central vacuole of plants: play roles in growth, storage, & rid of toxic substances

Mitoch­ondria

(has a double membrane and contains folds -- cristae)
- function: synthesize energy/ATP (cellular respir­ation -- Krebs Cycle and ETC)

Chloro­plast

- function: photos­ynt­hesis
(made of grana stacked together to make thylakoids inside the stroma)
1. amylop­lasts: stores starch and sugars
2. chromo­plasts: pigment synthesis and storage