Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

BIOSCI107 (MY OWN) > Cell Processes - Lecture 1 > Flashcards

Cell Processes - Lecture 1 Flashcards

1
Q

How thick is a membrane structure

A

8nm (8x10^-9 m)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

general features of a membrane (structure / barrier)

A
  • thin
  • flexible
  • sturdy
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

how can we describe a membrane structure

A

fluid mosaic model

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

what is a membrane made up of

A

50% lipid
50% protein
held together by Hydrogen bonds

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What is a lipid

A

barrier to entry or exit of POLAR substances

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

what are proteins?

A

“gatekeepers” - regulate traffic

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

can molecules cross the lipid bilayer?

A

some can, some cannot

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is the role of cholesterol in the lipid bilayer

A

it is scattered among a double row of phospholipid molecules
- is a lipid which can insert in phospholipid backbone
- can change composition or properties of lipid bilayer

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

what is the role of glycolipids in the lipid bilayer

A

it is scattered among a double row of phospholipid molecules
- is a sugar group
- attached to hydrophobic lipid molecule which can embed in lipid bilayer

NOTE: it is a sugar group in and out of the membrane

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Give the properties of phospholipids

A
  • comprises 75% of lipids
  • phospholipid bilayer = 2 parallel layers of molecules
  • each layer in the bilayer known as a leaflet
  • each molecule is amphipathic (has both polar & non-polar regions)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

features of membrane fluidity

A
  • membranes are fluid structures
  • cholesterol changes fluidity
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

features of lipids according to membrane fluidity

A
  • lipids can move around within the plane of the membrane leaflet
  • lipid rarely flip flop between the leaflets
  • due to reduced flip flop, lipid composition of leaflets can be asymmetric
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

what is membrane fluidity determined by

A
  • lipid tail length –> longer tail = less fluid of the membrane
  • number of double bonds –> more double bonds = increased fluidity
  • amount of cholesterol –> more cholesterol = decreased fluidity
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Two different types of membrane proteins and where they can be found

A
  1. Integral proteins
    extend into or completely across cell membrane
    (also known as a transmembrane protein)
  2. Peripheral proteins
    attached to inner or outer surface of cell membrane
    can be easily removed from it
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

features of integral membrane proteins

A
  • amphipathic
  • have hydrophobic regions which span hydrophobic core of lipid bilayer
  • hydrophobic region consists of non-polar amino acids coiled into helices
  • hydrophilic ends / regions interact with aqueous solution
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

what are the different functions of membrane proteins

A

Can act as:
- receptor proteins
- cell identity markers
- linkers
- enzymes (can form enzymes)
- ion channels
- transporter proteins

Ion channels & transporter proteins move things across cell membrane

17
Q

what does permeability mean

A

ability to cross membrane

18
Q

what causes selective permeability

A

the molecular organisation
^^ the membrane allows some substances to cross but excludes others

19
Q

How can be apply selective permeability to a lipid bilayer

A
  • permeable to non-polar, uncharged molecules (O2, N2, benzene)
  • permeable to lipid soluble molecules (steroids, fatty acids, some vitamins)
  • permeable to small uncharged polar molecules (water, urea, glycerol, CO2)
  • impermeable to large uncharged polar molecules (glucose, amino acids)
  • impermeable to ions (Na+, K+, Cl-, Ca2+, H+)
20
Q

How do large uncharged polar molecules AND ions move across the membrane?

A

via transport protein
^^ it moves them across the membrane

21
Q

How do substances which cannot permeate the hydrophobic core of the lipid bilayer get across? and give examples

A

membrane proteins mediate the transport of the substances across the membrane.
this is:
ion channels
transport protiens

22
Q

when does diffusion occur

A

if we have a difference in concentrations & molecules will move across the membrane until they reach equilibrium

23
Q

How does net diffusion work

A

net diffusion from a higher dye concentration to the region of lower dye

24
Q

How do we know equilibrium has been reached?

A

when the dye (or colour) is spread out evenly / evenly distributed

25
Q

What are the principles of diffusion

A
  • random mixing of particles in a solution due to a particles kinetic energy
  • more molecules move away from an area of high conc to an area of low conc
  • greater difference in concentration between 2 sides of the membrane = faster the rate of diffusion
  • higher temp = faster rate of diffusion
  • larger size of diffusing substance = slower rate of diffusion
  • increase in surface area = higher rate of diffusion
  • increasing diffusion distance = slower rate of diffusion
26
Q

what are the physical consequences of diffusion

A
  • rate of diffusion sets a limit on the size of cells of about 20nm
  • to increase diffusion a cell can increase membrane area available for exchange (diffusion) of a substance
  • thicker membrane = slower rate of diffusion
  • small distances = fast diffusion
27
Q

What are the two gradients across the cell membrane

A
  • concentration gradient
  • electrical gradient
28
Q

Concentration gradient

A
  • non charged molecules will diffuse down their concentration gradients

NOTE: driving force for dilution will solely be conc gradient because they are non-charged so no electrical gradient acting

the selective permeability of the membrane enables:
- a difference in concentration
OR
- concentration gradient across the membrane to be established

29
Q

electrical gradient

A
  • ions will be influenced by membrane potential in addition to their conc gradient

NOTE: electrochemical gradient drives

cells can maintain a difference in charged ions between the inside & outside of membrane establishing an electrical gradient or membrane potential

30
Q

what is the movement of ions influenced by

A

electrochemical gradient

31
Q

What do membranes mimic

A

capacitors: can seperate AND store charge

32
Q

ion gradients across the membrane

A
  • cells use ~30% of resting energy to maintain concentration and electrical gradients
  • gradients represent stored energy
33
Q

what is osmosis

A

net movement of water through a selectively permeable membrane from an area of high water concentration to an area of low water concentration

NOTE: we want to have hemeostatis

34
Q

features of osmosis

A
  • only occurs if membrane is permeable to H2O but not to certain solutes
  • this is the situation in biological membranes
  • if an osmotic gradient exists water will move to eliminate it
35
Q

osmosis equation and meaning of the variables

A

Pw = Pd + Pf

Pw = membrane permeability to water

Pd = through lipid bilayer
- small
- mercury insensitive
- temp dependent (lipid fluidity)

Pf = through water channel
- large
- mercury sensitive
- temp independent

NOTE:
- Pf is mediated by the aquaporins (9 isoforms)
- cells have different Pw because they express different aquaporin isoforms

36
Q

osmotic pressure

A

is the pressure applied to a solution to prevent inward flow of water across semi-permeable membrane

BIOSCI107 (MY OWN) (2 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions