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Flashcards in Week 3 - membranes Deck (14)
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1

phospholipids

- glycerol - 3 carbon molecule
- 2 fatty acid attach to glycerol- nonpolar
- phosphate group attached to gluycerol - polar
- lipids associate via NON-COVALENT interactions → free to move around bilayer

2

phospholipids and bilayers

- phospholipids spontaneously form MICELLES or LIPID BILAYERS
- structures cluser the hydrophobic regions of phospholipid towards inside & hydrophilic exposed to water environment
- basis of biological membrane

3

membrane fluidity

- must be fluid to work properly
- as temp cool, membranes switch to a solid state → this temp depends on type of lipid
- membranes rich in unsaturated fatty acids ar emore fluid than those rich in saturated fatty acids

4

bulk transport - exocytosis

movement of substances out of cell

5

bulk transport- edocytosis

movement of sunstances into cell
- phagocytosis: cells take in particular matter
- pinocytosis: cell takes in fluid
- receptor-mediated endocytosis →specific
- moleules take in after they bind to a receptor

6

membrane protein

- proteins determine membranes specific functions. →cell membranes & organelle membranes have a unique collection of proteins
- peripheral: loosely bound to surface of membrane
- integral: penetrate lipid bilayer TRANSMEMBRANE PROTEIN
- transport proteins: cannels permeases

7

permeability

- REPELS POLAR MOLECULESNOT NON-POLAR
- nonpolar molecules will move until conc. is equal on both sides
- limited permeability to small polar molecules

8

membranes - steroids

- at cold temp reduces packing of phospholipids →maintaining FLUIDITY
- at high temps cholesterol restrains movement of phospholipids making it LESS FLUID

9

CARRIER PROTEIN

tRANSPORT BOTH IONS & OTHER SOLUTES → SOME SUGARS AND aa

- conc. gradient across membrane
- carrier muse bind moleculwe
-saturation : rate limited by no. of transporters

10

Na+ - K+ pump

- direct use of ATP for active transport
- antiporter →moves 3 Na+ out of cell & 2K+ into cell, against conc. gradient
- affinity of carrier protein for either Na+ or K+ changes so ions can be carried across membrane

11

Na+ - K+ pump steps

1. carrier in membrane binds intracellular sodium
2. ATP phosphorylates protein w/ bound sodium
3. phosphorylation causes conformational change in protein, reducing its affinity for Na+ → diffuses out
4. conformation has high affinity for K+ extracellular. potassium bindsw/ exposed sites
5. binding of K causes dephosphorylation
6. dephosphorylation of protein triggers change to original conformation w/ low affinity to K →K diffuses into cell

12

cell membrane

- SEPARATEs a living cell form surroundings
- controls traffic in & out of cell
→ selectively permeable
→allows some substances to cross more easily than others

13

coupled transport

- uses ATP indirectly
- uses energy released when a molecule moves by diffusion to supply energy to active transport of a diff molecule
- symporter
- glucose - Na+ captures energy & moves glucose against gradient

14

facilitated diffusion

- molecules that cannot cross membrane easy move through proteins
- move from high to low conc.
- channel proteins: hydrophilic channel
- carrier proteins: bind specific to molecules