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BIOL 130 > Unit 4 - Membranes > Flashcards

Unit 4 - Membranes Flashcards

1
Q

Structure

Describe membrane phospholipid structure.

(4 sections)

A
  • polar head
  • phosphate
  • 3-C glycerol
  • fatty acid chain
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2
Q

Structure

Which end faces the water?

A

polar end

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3
Q

Structure

Describe movement of phospholipids.

A
  • spins/rotates in place
  • can swap within leaflets
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3
Q

Structure

Describe how temperature affects fluidity.

A
  • transition temeperature (Tm) is where a membrane can become a fluid or gel
  • if above Tm, membrane is fluid, more movement
  • if below Tm, membrane is gel-like
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4
Q

Structure

What factors affect Tm?

A
  1. Length of fatty acid chains: longer chains = higher Tm
  2. Double bonds: more double bonds = lower Tm
  3. Amount of sterol: e.g. cholestorol prevents phase changes
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5
Q

Structure

Describe homeo viscous adaptations

A

Adapting to lower temperatures:
* shorter fatty acid chains
* more double bonds

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6
Q

Structure

Describe the location of proteins in membranes.

A

Proteins are transmembrane, spanning across both leaflets

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7
Q

Structure

Describe protein movement.

A
  • Proteins move within the membrane
  • orientation is maintiained
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8
Q

Structure

Describe how epithelial cells prevent protein movement.

A
  • tight junctions prevent proteins from the top to cross into the bottom/sides of the cell
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9
Q

Structure

Describe membrane carbohydrates

A
  • sugars attatch to proteins
  • they attatch to non-cysotsolic side
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10
Q

Structure

Describe 4 steps of membrane formation.

A
  1. Fatty acids in cytosol, creating phospholipids
  2. Phospholipids attatch to the cytosolic side in ER
  3. Phospholipids cross leaflets to even out
  4. In golgi, flippase move phospholipids between leaflets to sort them out
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11
Q

Structure

Describe distribution of phospholipids and cholestorol between leaflets.

A
  • phospholipids are distributed unevenly
  • cholestorol is always even on both sides
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12
Q

Transport

Name 3 ways substances can enter a cell.

A
  1. Directly through lipid bilayer
  2. Membrane proteins
  3. Engulfing
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13
Q

Transport

Describe water movment across a membrane.

A
  • moves in both directions
  • moves from low concentration of solutes to high until equilibirum (osmosis)
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14
Q

Transport

Hypotonic Solution

A
  • lower concentration of solutes
  • water moves into cell
  • ideal for plants
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15
Q

Transport

Hypertonic Solution

A
  • higher concentration of solutes
  • water moves out of cell
16
Q

Transport

What molecules can freely cross bilipid membrane?

A

small, uncharged, polar/non-polar moleculres

17
Q

Transport

Compare channel and carrier proteins.

A
  • channels can allow anything to pass as long as it can fit and open
  • carriers have a particular binding-site, transports molecules one at a time
18
Q

Structure

Which phospholipids are moved to the cytosolic leaflet by flippase?

A

PS and PE

19
Q

Transport

Describe ion channels.

A
  • highly selective based on size and charge
  • allows ions to move along concentration/electrical gradient
  • can move ions in both directions
20
Q

Describe the 3 ways ion channels open/close

A
  1. voltage gated: inside of membrane becomes positively charged
  2. ligand-gated: ligand binds to a site on channel
  3. mechanically-gated: pressure opens/closes the channel
21
Q

transport

Describe carrier proteins

A
  • has a binding site that flips at random
  • molecules pass through diffusion one at a time
  • moves along gradient
  • binding site can be blocked by inhibitors that fit in binding site
22
Q

Transport

What are the two types of transports that go against a gradient?

A

Active Transport and Coupled Transport
(co-transport)

23
Q

Transport

Describe active transport

A

uses (releases) enegry to move ions against their concentration gradients

24
Q

Describe the Na-K ATPase

A
  • ATP pump that moves sodium into cell and potassium out
  • 3 Na per 2 K
  • coupled reaction: ATP to ADP
25
Q

Transport

What is the significance of the Na+ gradient?

A

Transports glucose, amino acids and other molecules to cell, useful for co-transport

26
Q

Transport

What is coupled transport?

A

two substances (usually a molecule and ion) are transported across a membrane simultaneously

27
Q

Transport

What is a symport?

A

a molecule and ion move in the same direction across membrane

28
Q

Transport

What is an antiport?

A

a molecule and ion move in opposite directions across membrane

29
Q

Transport

In which direction does the ion usually move?

A

The ion usually moves along its gradient to create a driving force for the coupled molecule

30
Q

Transport

Describe glucose-sodium symport

A
  • occurs in intesntinal epithelium cell
  • Na+ moves along gradient and glucose moves against graidient into the cell
  • Na-K ATPase continues to move sodium out of cell to maintain gradient
31
Q

Transport

Describe proton-driven symport in plant cells.

A
  • co-transport occurs with H+ ions
  • there is an H+ gradient
  • H+ ATPase is used to maintain gradient
32
Q

Transport

What mutation relating to membrane transport could occur?

A
  • transporters are proteins, coded by DNA
  • a mutation in an important transporter is very bad

BIOL 130 (3 decks)

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