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Biology A level > 2.1.5 - Biological Membranes > Flashcards

2.1.5 - Biological Membranes Flashcards

1
Q

Phospholipid structure

A

A glycerol molecule
Two fatty acid tails (saturated and unsaturated)
Phosphate group

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2
Q

Properties of phospholipid

A

Phosphate group is polar —> hydrophilic
Fatty acid tails are non polar —> hydrophobic

(Amphipathic)

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3
Q

Why does soap dissolve the membrane easily

A

Membranes are made from lipids

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4
Q

What is selective permeability

A

When what goes in and out of the cell is regulated by only letting certain things in and out

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5
Q

Major molecules in cell membranes

A

Phospholipids

Proteins

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6
Q

Amphipathic

A

The molecule has dual nature (hydrophobic and hydrophilic)

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7
Q

What roles do proteins play in transport

A

Regulation

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8
Q

What kinds of cells have cell walls

A

Plant
Bacterial
Fungal

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9
Q

What are glycoproteins made from

A

Proteins

Sugars

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10
Q

Example of a glycoprotein

A

Antibodies - important in immune response

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11
Q

What are glycolipids made of

A

Fats

Sugars

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12
Q

Why can’t water pass through the phospholipids

A

The inside is non polar

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13
Q

How do proteins assist in transport

A

Allow big things and things that have a charge to move across the membrane

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14
Q

What is a plant cell wall made of

A

Cellulose

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15
Q

What is a bacteria cell wall made from

A

Peptidoglycan

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16
Q

What is a fungal cell wall made from

A

Chitin

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17
Q

Function of chlolesterol in cell membranes

A

Regulates fluidity of membrane by keeping phospholipids slightly apart or pulling them closer
Hydrophilic ends interact w/ heads and hydrophobic end interacts w/ tails; pulls them together
Prevent phospholipids from grouping together too closely and crytsallising

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18
Q

Function of glycoprotein in cell membrane

A

Cell adhesion - binding site for hormones and drugs
Cell signalling to coordinate activities of organisms
Antigens for the recognition of ‘self’
Acts as receptor

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19
Q

Function of glycolipid

A

Form cell markers/ antigens

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20
Q

Function of carbohydrates in cell membrane

A

Hydrophilic molecules that sit on the cell surface membrane and attracts water with dissolved solutes

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21
Q

Carrier protein

A

Changes shape to allow specific molecules in and out of the cell

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22
Q

Channel protein

A

These provide a hydrophilic channel that allows the passive movement of polar molecules down a concentration gradient

Water filled channel inside is lined with hydrophilic amino acids

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23
Q

Integral/ intrinsic proteins

A

Proteins that span the whole membrane

Either channel or carrier proteins

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24
Q

Protein receptor site

A

Acts as receptors to detect hormones and/or drugs

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25
How do carrier proteins work
Molecule binds Carrier protein changes shape Releases molecules on the other side
26
When is diffusion rapid
Small | Non-polar molecules
27
Facilitated diffusion
Involves carrier and channel proteins within the cell membrane. These help transport large, polar molecules e.g. glucose, across the membrane
28
Functions of a cell membrane
Can be a site of chemical reactions - contain enzymes Cell signalling Create conc. gradient Has antigens so the immune system recognises it as ‘self’ Separates contents from outside - barrier (cell or organelles) Regulates transport of molecules in/out of a cell or organelle Seperates metabolic pathways
29
Factors affecting diffusion
``` Temperature Molecule size Conc. gradient Diffusion distance Surface area ```
30
Cell membrane permeability at higher temps
Phospholipids moving around so fluidity and permeability increases (more kinetic energy) Cholesterol reduces the fluidity The proteins could denature and the bilayer could be completely permeable
31
What does water dissolve
Polar solutes
32
What does ethanol dissolve
Membranes, disrupting cells which is why alcohols are used in antiseptic wipes
33
How do solvents affect permeability
Non polar or less polar solutes will disrupt membranes as the tails no longer orientate towards the middle. The membrane will become more fluid and more permeable
34
What happens if animal cells are put into pure water
Cell bursts open, it is cytolysed
35
What happens if animal cells are put in a solution with low water potential
Cell shrinks and appears wrinkled - it is crenated
36
What happens if a plant cell is put in pure water
Plant cell wall prevents bursting. Membrane pushes against cell wall - cell is turgid
37
What happens if a plant cell is put in a solution with very low water potential
Plasma membrane pulls away from the cell - it is plasmalysed
38
Water tendency
Measure of the tendency of water molecules to diffuse from one region to another Measured in kPa
39
What is water potential affected by
The amount of solute it contains The greater the amount of solute it contains, the lower or more negative the lower water potential
40
Osmosis
The passive movement of water from an area of high water potential to an area of low water potential across a partially permeable membrane
41
Active transport
Movement of substances from low to high conc. across a cell membrane, using ATP and protein carriers (against a conc. gradient)
42
What do carrier proteins combine reversibly with
Specific solute molecules or ions. They also have a region that binds to and allows the hydrolysis of a molecule of ATP to release energy
43
Sodium potassium pump
Carrier proteins binds 3 Na+ ions and 1 ATP | ATP is hydrolysed to release energy and the carrier protein changes shape
44
Tonicity
How much solute is in the solution
45
Hypotonic
Less solute | Higher water potential
46
Hypertonic
More solute | Lower water potential
47
Highest water potential
0 kPa | Pure water - no solute dissolved
48
Endocytosis
Taking in large particles into the cell using vesicles and ATP Csm invaginates when it comes into contact w/ substance Enfolds membrane til it fuses --> forms vesicle Vesicle pinches off and moves into cytoplasm to necessary organelle
49
Phagocytosis
Endocytosis carries out by phagocytic cells
50
Pinocytosis
Taking in liquid into the cell
51
Passive transport
Diffusion Facilitated diffusion Osmosis
52
Bulk transport
Movement of molecules through a membrane by the action of vesicles
53
Thickness of plasma membrane
7.5 nm
54
How factors affect the rate of diffusion
(Temp x SA x Conc. diff)/(diffusion distance x size of particle)
55
Receptor mediated endocytosis
Transports LDLs and viruses into the cell only | Requires ATP
56
Investigating cell membrane permeability
Cut 5 equally sized beetroots w/ a cork borer Rinse and dry - to remove all pigment Add beetroots to diff test tubes w/ 5cm^3 of water Add each tt to a diff water bath w/ diff temp for same amount of time Remove beetroot and using a pipette transfer remaining sol. to cuvette until 3/4 full Use blue filter and measure abs High abs, more pigment released, more permeable
57
Investigating water potential of plant cells
Prepare sucrose sol. of diff conc. Use cork borer to get identically sized potato cylinders Measure mass w/ mass balance Place each cylinder is diff conc. solution for same amount of time Calculate % change in mass Plot conc. on x and % change on y to find when conc. was isotonic
58
Examples of model cells
Agar jelly Visking tubing Gelatine cubes These have a similar cytoplasm to our cells
59
Investigating diffusion using model cells (conc.)
Prepare agar jelly / indicator and alkali (pink) Prepare tt w/ diff conc. of acid Cut equal sized cubes from agar jelly and place into tt Use stopwatch and record time taken to go colourless Higher conc. of acid = less time to go colourless Repeat at least 3x and calculate mean
60
Why do we do repeats
Calculate mean | Reduce effect of random error
61
Precision
Having all your values close to EACH OTHER
62
Accuracy
Having all your values close to the TRUE VALUE
63
Why does facilitated diffusion not use ATP
Molecules have their own kinetic energy | Uses gradient
64
Which type of fatty acid tail contributes most to fluidity
Unsaturated
65
Intrinsic proteins
Channel proteins Carrier proteins Glycoproteins
66
Extrinsic proteins
Present in one side of bilayer Hydrophilic R groups on outer surface Can be present in either layer and some move between layers
67
Process of active transport
Molecule binds to receptor in channel of carrier protein Binding of phosphate causes proteins to change shape - opening up to the inside Molecule released to inside of cell Phosphate released and recombines w/ ADP Carrier protein returns to orig shape
68
Processes requiring ATP as an immediate source of energy
Active transport Exocytosis Endocytosis

Biology A level (32 decks)

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