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AS Biology > 4) Cell membranes and Transport > Flashcards

4) Cell membranes and Transport Flashcards

1
Q

how thin is the cell surface membrane ?

A

7 nm

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2
Q

what is the phospholipid structure ?

A
  • polar phosphate head (hydrophilic)
  • hydrophobic fatty acid (lipid) tails
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3
Q

what does hydrophobic mean ?

A

no electrical charge, so not attracted to water molecules

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4
Q

what does hydrophilic mean ?

A

has an electrical charge, and is attracted to water molecules

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4
Q

what is a glycoprotein ?

A

carbohydrate attached to a protein

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5
Q

difference between placement of integral and peripheral proteins ?

A
  • peripheral : on the edge or outside (do not cross middle line)
  • integral : cross the middle line
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6
Q

state the roles of a phosphate head

A
  • stability
  • hydrophilic/attracted to water
  • attracted to extracellular water/ water in cytoplasm
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7
Q

state the roles of a fatty acid tail

A
  • fluidity = unsaturated
  • stability = hydrophobic interactions between tails
  • barriers to hydrophilic substances (eg. glucose/ions)
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8
Q

state the roles of cholesterol

A
  • stability between fatty acid tails
  • prevents passage between tails
  • decreases fluidity
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9
Q

state the roles of glycolipids

A
  • stability (hydrophobic)
  • receptor for signal molecule
  • cell recognition (can be an antigen)
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10
Q

state the roles of peripheral proteins

A
  • cell recognition/ antigen
  • cell adhesion (cells stick together)
  • eg: glycoproteins
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11
Q

state the roles of integral proteins

A
  • moves polar substances/ions through membrane
  • transport proteins (channel/carrier)
  • pumps (active transport)
  • membrane bound enzymes
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12
Q

state the roles of glycoproteins

A
  • cell recognition (antigen)
  • cell signalling
  • receptor for hormones (neurotransmitters)
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13
Q

the main stages of cell signalling

A
  • ligands (cell signalling molecules) are secreted from a cell (the sending cell) into the extracellular space.
  • They are then transported through the extracellular space to the target cell.
  • The ligands bind to the surface receptors (specific to that ligand) on the target cell. : These receptors are formed from glycolipids & glycoproteins.
  • The message carried by the ligand is relayed through a chain of chemical messengers inside the cell = triggering a response.
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14
Q

2 differences between active and passive transport

A
  • Active : uses ATP
    : goes against concentration gradient. (low –> high)
  • Passive : does not use ATP
    : goes down the concentration gradient. (high –> low)
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15
Q

What are the 2 types of active transport and also their types?

A
  • Active transport : pumps & carrier
  • Bulk transport : endocytosis & exocytosis
16
Q

what are the 3 types of passive transport?

A
  • Simple diffusion
  • Osmosis
  • Facilitated diffusion : channel & carrier
17
Q

what is diffusion ?

A

net movement of molecules from a region of high concentration to low concentration, using energy from the random movement of particles.

18
Q

what are some factors affecting diffusion ?

A
  • concentration gradient (greater the diff in concentration between 2 regions, greater amount diffuses)
  • distance (shorter the distance, greater the diffusion)
  • area (larger the area, greater the diffusion)
  • size/type of diffusing molecules (smaller / soluble will diffuse faster)
19
Q

what can go through the lipid bilayer, and what cannot ?

A
  • can go through : hydrophobic & small uncharged molecules (H20)
  • cannot : large uncharged molecules & ions (Na+)
20
Q

what is facilitated diffusion ?

A

the transport of polar molecules and ions into and out of a cell. It involves the use of carrier and channel proteins.

21
Q

state 5 differences between channel & carrier proteins

A

channel proteins (position fixed)
- transport ions
- soluble molecules diffuse thru the pores
- high transport rates
- do not bind with solute molecules it transports
- only transport water soluble molecules

carrier proteins (flip between 2 conformations)
- transport molecules
- solute molecules bound to one side, released from other side
- low transport rates
- consist of alternative solute-bound conformations
- transport both water soluble and insoluble molecules.

22
Q

what is osmosis ?

A

diffusion of water molecules from high water potential to low water potential through a partially permeable mebrane

23
Q

what is the highest water potential ? (and unit)

A

0 kPa = water

24
Q

define hypotonic, isotonic, and hypertonic

A
  • hypotonic : higher water potential than the cell (turgid)
  • isotonic : same water potential as cell.
  • hypertonic : lower water potential than cell (flaccid/plasmolysed)
25
Q

state basic stages of active transport

A
  • particle enters the pump
  • binds to a specific site
  • uses ATP to change shape of pump
  • particle released on the side w higher concentration
  • pump then returns to its original shape
26
Q

describe endocytosis

A

(into cells)
- part of plasma membrane pulled inwards
- a droplet of fluid becomes enclosed when a vesicle is pinched off
- vesicles can then move through the cytoplasm carrying contents

27
Q

describe exocytosis

A

(out of cells)
- vesicles FUSE w plasma membrane
- contents of vesicle expelled
- membrane then flattens out again

28
Q

differentiate between phagocytosis & pinocytosis

A
  • Phagocytosis : bulk uptake of SOLID material + cell EATING.
    (eg: engulfing of bacteria by white blood cells)
  • Pinocytosis : bulk uptake of LIQUID + cell DRINKING.
    (eg: absorb nutrients from food)
29
Q

Summary of differences between passive and active transport

A

(pg. 16 of 31 from chapter 4 notes )

30
Q

relationship between surface area and diffusion

A

greater the surface area, faster the diffusion

31
Q

describe turgid plant cell

A
  • hypotonic solution
  • higher water potential than the cell, so water moves into the cell
  • protoplast swells and presses against cell wall
32
Q

describe plasmolysis (flaccid)

A
  • hypertonic solution
  • lower water potential than the cell, so water moves out of the cell
  • protoplast pulled away from cell wall
33
Q

explain why phospholipds are able to form bilayer

A
  • polar hydrophilic phosphate groups on the outside.
  • so heads face watery env & tails face away / each other
34
Q

explain how the structure of phospholipid molecule makes it suitable for its function

A
  • polar hydrophilic phosphate heads face outwards into water.
  • alternatively 2 layered structures called bilayers can form in sheets.
  • forms hydrogen bond with water & stabilises membrane.
35
Q

how does inner membrane differ from outer membrane

A
  • fewer channel proteins
  • less unsaturated fats
  • reduced gaps between membrane molecules
36
Q

2 similarities between active transport and faciliated diffusion

A
  • both use carrier proteins
  • both are specific/ have specific binding site.

AS Biology (11 decks)

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