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BIO 130 > Unit 4 Biological Membranes > Flashcards

Unit 4 Biological Membranes Flashcards

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Biology 101 flashcards
1
Q

type of proteins

A

protein structure - integral membrane proteins - transmembrane proteins involved in transport

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2
Q

transmembrane proteins category

A

ions channels, carrier protiens, pump/ATPases

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3
Q

Pumps/ATPase

A

primary, active transport, directly burning ATP, Na+/K+

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4
Q

carrier proteins

A

uniport, coupled transport = co-transport = indirect active transport = secondary active transport (symport na - glucose, antiport - moves ions)
know which moves against or with gradient

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5
Q

biological membranes
where are they located?

A

all cells have plasma membrane

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6
Q

difference between eukaryotic and prokaryotic

A

eukaryotic contain membrane bound organelles
nuclear envelope, double membranes of mistochondira and chloroplasts
endoplasmic reticulum, golgi, lysosomes, vacuoles, transport vesivles

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7
Q

membrane functions

A

all functions (except one) come from proteins in cell.
- provide selectively permeable barrier, prevent unrestricted exchange of molecules
- trasport solutes, exchange molecules across membrane
- respond to external signals, signal transduction… signals travelling from distance or from nearby cells
- energy transduction, conversion of one form of energy into other (inner mitochondrion membrane , motor protein force, of not no abilit to establish proton gradient
- compartmentalization, creates separate environments for differenct activities
- scaffold for biochemical activities

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8
Q

movement of bilayer

A

phospholipid bilayer, polar heads and non polar tails
not statically arranged, freely moving fluid mosaic model

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9
Q

Membrane Fluidity and lipid composition

A

fluid state must be maintained for normal cell function
membrane fluidity - how easily lipid molecules moves within membrane leaflet

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10
Q

strategies for adjusting membrane fluidity

A

alter alignment of phospholipid tails
tightly packed tails - membrane more viscous, less fluid
freely moving tails - higher fluidity

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11
Q

How to alter

A

alter length of fatty acids,
alter degree of saturation
alter cholesterol content (warm conditions, more cholesterol, more fluid)

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12
Q

How does temperature impact fluidity

A

at and above room temperature phospholipids in membranes are fluid
as temp drops fluidity decreases (and permeability)
at VERY low temp, hydrophobic tails pack together and membrane gels (solidifies)

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13
Q

What does cholesterol do to transition temperature?

A

Cholesterol lowers transition temperature

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14
Q

how do organisms that aren’t warm blooded regulate temperature

A

Cells that are part of organisms that aren’t warm blooded have to have these mechanisms available to regulate lipid content of their membranes tp [revent gelling and loss of integrity

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15
Q

Endoplasmic Reticulum

A

location of initial membrane synthesis
enzymes needed to produce phospholipid membrane are localized in ER in cytozol
find free fatty acids, sterify them, add polar head groups, (they are amphipathic)
they start to insert spontaneously in leafelet
start to distort bilayer
the cell gets from cytosolic leafelet to non cytosolic
need enzyme to power the process: take phospholipids from leaflet and add to other

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16
Q

Asymmetry of Lipid Bilayer

A

large population of PC, PS, and PE on cytosolic side,
large population of SM, PC and Cholesterlo on other side but cholesterol randomly distributed

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17
Q

Memrane assembly

A

Role of Golgi Apparatus
vesicles leave the ER, insert into Golgi membrane
flipases take randomise distribution, move PS and PE to cytosolic leaflet
leave golgi as vesicles fuse with plasma membrane
the assymetry maintained past the golgi

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18
Q

Which aspect of lipid component is essential to membrane function

A

permeability barrier (structural)

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19
Q

Protiens in membrane

A

essential for majority of function (50% mass of plasma membrane in protein)
lipids are small - 50x more lipid molecule than protein molecules

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20
Q

how do proteins associate with membranes?

A

integral - have to destroy phospholipid bilayer to get proteins out
peripheral - we dont, remove without distruction

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21
Q

types of membrane proteins

A

Integral: transmembrane proteins
monolayer associated
lipid linked
Peripheral - protein linked, covalent bond easily broken

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22
Q

Polypeptide chains inside membrane

A

usually cross as alpha helices
side chains allow insertion of pptde into membrane

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23
Q

how can hydrophilic channels be formed inside membrane

A

use multiple helicese to create pores
the transmembrane alpha helix
surface of helicese hydrophobic, and in center make polar
now have polar chanel inside of hydrophobic system

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24
Q

protein baskets

A

proteins folded into pleated sheets can form pores
side of baskets can have different charges to form hydrophobic/philic chanels

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25
Q

Movement of proteins in lipid bilayer

A

lipids always in motion (fluid environemnt)
proteins can also move freely, doesn’t stay in one location

26
Q

How do cells restrict movement of membrane proteins

A

cells want localized function of protiens so restrict their movement by:
anchor to cortex
physically coupled with extracellular matrix
form cell-cell junctions (restricts motion becuase interacts with other cell)
Diffusion barriers: synthesize proteins in plasma membrane restricts free diffusion on molecules from one side to other of barrier

27
Q

membrane protein distribution in an epithelium

A

lumen on one side, bring nutrients in (through transport protein but no good function if it was on the bottom side of cell)

28
Q

Carbs important

A

plasma membrane of animal cells decorated with sugars
important functions in the cell membrane
identification, etc
non cytosolic phase highsly glycosilated, outer leaflet has glycolipid

29
Q

Membrane transport - how can certain molecules spontaneously move across PLBI

A

lipid bilayers block passage of polar (water-soluble) molecules
substances can enter by - passing directly through LBI, being transported by membrane proteins acting as carriers or channels, being engulfed by cell avoiding passing through membrane

30
Q

How do molecules move?

A

molecule randomly spread out ( increasing entropy) until reaches equilibrium - diffusion
at that point - no net flux

31
Q

Diffusion across a Permeable Barrier

A

molecules diffuse down conc gradient to equalize their concentrations on either side
dynamic equilibrium
net conc change across membrane = 0

32
Q

Osmosis

A

movement of water do equalize concentration of solute
diffusion down concentration gradient
once water equal on both sides, no net movement of water

33
Q

osmotic tone

A

isotonic - rate in = rate out

34
Q

Types of solutions

A

hypotonic - cell swells, net water gain
isotonic - no net loss or gain
hypertonic - net water loss cell shrinks

35
Q

what is ideal osmotic tone for plant cell

A

hypotonic
turgor pressure: pressure of cell contents agains cell wall in plant and bacterial cells
turgid, flaccid, plasmolyzed

36
Q

what moleculse can pass through membranes?

A

most:
small nonpolar molecules (O2, CO2, N2, steroid)
small uncharged polar molecules (H2O, ethanol, glycerol)
[larger uncharged polar molecules (AA, glucose, nucleasides)
ions] - need to be transported through protein transporters
least

37
Q

fluidity membranes impact
a) the diffusion of lipids within each leaflet,
b) diffusion of lipids between membrane leaflets,
c) diffusion of proteins within each leaflet

A

A and C

38
Q

Compared to inner (cytosolic) leaflet, the outer leadlet of the plasma membrane of mammalian cells

a) consist of the same proportions of different phospholipids
b) consists of different phospholipids but has similar cholesterol content
c) has higher cholesterol content
d) has higher carbs content
e) both b and d

A

both b and d

39
Q

intergal membrane proteins stay embedded in membranes becuase of

a) osmotic pressure from proteins outside cell
b) diffusion of proteins from the cytoplasm to the membrane
c) locations of their polar and nonpolar amino acids
d) their large size which does not allow them to pass throuh the membrane

A

c) locations of their polar and nonpolar amino acids

40
Q

Why don’t bacterial cells burst in hypotonic solution

a) bacteria that survive in hypotonic environments have very low internal solyte concentrations
b) the bacteria will gain some water from their surroundings, but expel the additional water through specalized outlets called aquajets
c) Bacteria have intracellular organelle that enables them to expel excess water
d) bacteria have cell wall that prevents lysis

A

d) bacteria have cell wall that prevents lysis

41
Q

Membraine proteins
mechanisms of transport

A
  • passing directly through lipid bilayer
  • being transported across bilayer by membrane proteins acting as carriers or channels
  • being engulfed by the cell avoiding passing through the membrane
42
Q

Transporters

A
  • membrane proteins acting as carriers or channels
43
Q

channel protein

A
  • tunnel
  • doors that open and close connecting one side of membrane to other
  • passageways for specific molecules
  • detect size and charge, but anything with the right conditions can pass
44
Q

carrier proteins

A
  • shuttle/trnsporter
  • opening to one side, closure to the other
  • require molecule to fit particular binding site, often only one molecule at a time can be transported
45
Q

Passive transport

A

move of molecules down their concentration gradient
high potential energy to low potential energy
high areas of concentration to low concentration areas
simple diffusion, channel mediated, transporter mediated

46
Q

active transport

A

proton pumps in electron transport chain
pumps need energetic input
moving molecules from low potentail energy state to high potential energy state
against concentration gradient
(can participate in both active and passive transport)

47
Q

Ion Channels

A

discriminate on charge and size
usually highly selective
much faster carriers
bidirectional
ion flux determine by both electrical and concentration gradients (electochemical gradient)

47
Q

electrical gradient

A

whether it is being attracted across membrane (opposite charged molecules) or repelled (by like charges)

47
Q

what determines whether channels are open or closed

A

voltage gated
ligand gated (extracellular ligand)
ligand gated (intracellular ligand)
stress gated - pressure on membrane causes channel to open

48
Q

carrier proteins: passive transport

A

binding of solute at specific sute temporarily changes shape of carrier protein
solute moves down concentration gradient so carrier protein FACILITATES PASSIVE DIFFUSION
can work in both directions

49
Q

GLUT1 (glucose transporter in mammalian cells)

A

allow glucose but not fructose
D- glucose but not L-glucose

50
Q

Features of Membrane Carrier Proteins

A

specificity
passive (fascilitates diffusion)
saturable
can be inhibited/blocked by substances resembling normal carbo (substrate)

51
Q

Carrier proteins: Active Transporters or Pumps

A

use energy to move ions agains gradient
transport must be closley coupled to energy release
- hydrolysis of ATP
- absorption of light, movement of electrons, movenets of another molecule down its conc. gradient

52
Q

Sodium - Potassium ATPase

A
  • first pump discovered in nerve cells of crabs
  • only present in animal cells
    -moves 3 Na out, 2 K in
    coupled to hydrolysis of ATP - change shape becuase of phosphate group
53
Q

Significance of of Na/K-ATPase

A

both membrane protein and enzyme
present in ALL animal cells (1/3 of energy produced in animal cells)
major contributer to basal metabolic rate
target of many drugs
helps maintain Na+ gradient (high out, low in) that is used to move other molecules (glucose, AA)

54
Q

carrier proteins and coupled transport

A

carrier proteins - uniport
coupled transport - symport and antiport

55
Q

Glucose-Na+ Symport in Intestinal Epithelium

A

relies on being able to move glucose into cell against conc gradient by using Na+ down conc gradient
bound on extracellular face of membrane, causes conformational change

56
Q

Glucose transport across the Gut lining is a team effort

A

intake of glucose across gut lining into blood stream
function of transmembrane proteins, diffusion barriers, specific locations of diffusion
tight junctions, adhere two membranes of adjacent cells together
separates epithelial cells in the gut into two different faces
top face of cell high conc of glucose, need active transport (Na glucose symporter) to bring glucose into bloodstream
GLUT 1 transporter can also bring glucose in through passive transport
all system fails in NaK fails to work
secondary active transport mechanism

57
Q

Membrane Transport in Animal vs Plant Cells

A

significant difference
in animal move monovalent ions to drive mechanisms
plant cells pump protons, fuffiling capacity of NaK pumps

58
Q

Membrane transporter and Gene expression

A

differential structure of membranes related to the difference of protiens within different organelles/cells
membrane depends on genes
expression of cell, time, region
diversity of innermembrane transport distinguishes different cell type from one another
particular mutations -channelopothies
cystic fibrosis - chloride ion transport channel results in deletion of AA, water follows cl- by osmosis, ion channel defect results in 85% loss of channels means water isn’t getting causing thick mucus in lungs
dictate how cell is going to function based on protein inside of cell

59
Q

membrane carrier proteins are distinguished from ion channels by following features
a) carrier proteins move solutes down a gradient, whereas ion channels can move ions down or agaisnt a gradient
b) membrane carriers are specific in what they carry, while channels will let anything through that has the correct charge
c) membrane carrier proteins can become saturated if the concentration of their corgo molecule is high, whereas channels allow passage of ions at very high rates as long as there is diffusion gradient
d) gene mutations can cause dysfuntion of ion channels but not carriers
e) carrier are integral membrane proteins whereas ion channels are merely holes in lipid bilayer

A

c) membrane carrier proteins can become saturated if the concentration of their cargo molecule is high, whereas channels allow passage of ions at very high rates as long as there is diffusion gradient

BIO 130 (5 decks)

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