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A Level Biology > Transport Across Membranes > Flashcards

Transport Across Membranes Flashcards

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1
Q

What is a plasma membrane

A

All membranes sighing and around all cells and organelles

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2
Q

Structure of plasma membrane

A 
Phospholipid bilayer with hydrophilic heads facing outside and tails facing each other 
Proteins (extrinsic and intrinsic)
Cholesterol in animal cells 
Glycolipids 
Glycoproteins
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3
Q

Cell - surface membrane is —— membrane

A

Plasma

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4
Q

Mitochondria membrane called/is

A

Two plasma membranes wrap around organelle

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5
Q

Phospholipid in plasma membrane purpose

A

Allows lipid soluble substances to enter and leave cell
Prevent water soluble substances entering and leaving cells
Make the membrane flexible and self sealing

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6
Q

Purpose of proteins in plasma membrane

A

Extrinsic - give mechanical support, or as cell receptors for hormones or in conjunction with glycolipids
Intrinsic - Protein channels or Carrier proteins for allowing water soluble molecules to pass or for active transport
Also help dells adhere together

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7
Q

What characteristics of molecules allow it to pass through phospholipid membrane by simple diffusion

A

Small,non polar apart from water which is small hence passes through

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8
Q

Extrinsic proteins means

A

Proteins that do not extend through bi layer/ on surface

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9
Q

Intrinsic proteins mean

A

Extend all the way through membrane

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10
Q

Phospholipid has

A

Single phosphate head and two fatty acid tails

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11
Q

Cholesterol purpose in bilayer only in animal cells k

A

Pulls fatty acid tails together, limiting movement
Reduces lateral movement of molecules including phospholipid
Less fluid membrane at high temperature
Prevents the leakage of water and dissolved ions from cells

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12
Q

Glycolipids made of

A

Carbohydrate covalently bonded to a lipid

Carbohydrate extends out of bi layer into watery environment where it acts as a receptor for specific chemicals

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13
Q

Blood type depends on

A

Type of receptor glycolipids

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14
Q

Glycolipids function

A

Recognition sites
Stability of the membrane
Help cells to attach to one and other and form tissues

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15
Q

Glycoproteins are

A

Carb chains are attached to extrinsic proteins on the outer surface more for hormones and neurotransmitters

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16
Q

Glycoproteins function

A

Recognition sites for neurotransmitters and hormones
Helps cells attach to each other and form tissues
Allows cells to recognise each other for example lymphocytes can recognise an organisms own cells

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17
Q

Why cholesterol only in animal cell membrane

A

Because animal cells don’t contain cell walls so need added protection and strength from cholesterol

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18
Q

Why can water pass through plasma membrane

A

Small enough

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19
Q

Fluid mosaic model of plasma membranes

A

Large macromolecular proteins floating in a sea of phospholipids

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20
Q

Why are plasma membranes described as adhering to the fluid mosaic model? 2 marks

A

The glycoproteins are embedded within the phospholipid hence like a mosaic and float and move within a sea of phospholipids hence fluid

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21
Q

Factors that affect the fluidity of plasma membranes

A

Saturated/unsaturated more flows if saturated
Temperature if higher more random movement so more fluid but then becomes disordered
Length

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22
Q

Osmosis definition

A

The passage of water from a region of high water potential to a region of low water potential, through a selectively permeable membrane.

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23
Q

Water potential

A

Psi = trident like symbols
Measures in kilopascals
Pressure created by water molecules
Under standard conditions (25°C and 100kPa) water potential is 0.

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24
Q

Increase in solute causes an —— in water potential

A

Decrease

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25
Increase in solute and concentration cause an —— in water potential
Decrease
26
In terms of positive/ negative how does water move
Less negative to more negative
27
Water potential is equal inside cells and outside in solution when
There is no net movement of water
28
Osmosis will continue till
Enough H2O molecules will pass through the selectively permeable membrane for dynamic equilibrium to be obtained.
29
What is the highest value of water potential = only when water is pure.
0
30
A hypotonic solution
Higher concentratation in solution than in cell
31
A hypertonic solution
Higher concentration of solute in cell than solution
32
If RBC is in a solution with a higher water potential (hence less negative) then what happens
Absorbs water, then cell surface membrane will break (haemolysis)
33
A lower water potential
Means a less negative solution hence the cell will absorb water
34
A lower water potential of solution means
Means more negative hence water leaves cell
35
RBC in a soo with lower water potential hence more negative
Water leaves cell and cell shrinks Haemoglobin is more concentrated hence darker Cell shrivels and becomes cremated
36
Blood plasma and RBC have the same
Water potential
37
Plant cell places in a sol with higher water potential hence less negative
Water enters the cell Protoplast swells Cell is turgid
38
Wall of protoplast pushed against cell wall is
Turgid
39
Plant cell in sol with equal water potential
No change | Incipient plasmolysis when protoplast is beginning to pull away from the cell
40
Incipient plasmolysis
When protoplast begins to pull away from the cell
41
When plant cell is place in a solution with lower water potential hence more negative
Water leaves cell Cell shrinks Protoplast pulls complexity away from cell wall Plasmolysis
42
Plasmolysis
Protoplast has been complete pulled away from cell wall
43
A hypotonic sol will have a —— water potential
Higher
44
A hypertonic sol will have a —— water potential
Lower
45
Diffusion definition
The net movement of molecules/ions from a region of high concentration to a region of low concentration until they are evenly distributed.
46
Diffusion is passive
Energy comes from the natural inbuilt motion of particles rather than an external source like ATP
47
Facilitated diffusion
movement of large/charged/polar molecules/ion through the plasma membrane vis transmembrane channels and carriers - no energy required
48
Why do charged/polar molecules not diffuse essily through plasma membrane
Due to Hydrophobic fatty acid tails
49
Protein channels are/do
Water filled hydrophilic proteins, hence allow water soluble molecules to pass Very selective - only opens up in the presence of a specific ion Ion bonds to protein causing a change of shape that closes one side of the membrane and opens up the other
50
Carrier proteins
When s molecule like glucose binds with its specific protein, a change in shape causes the glucose to be released to the inside of the membrane
51
What is the active transport def
The movement of molecules/ions from a region of low concentration to a region of high concentration (into/out of cell) using ATP and carrier proteins (also know as pumps)
52
Direct Active Transport Process
Intrinsic carrier proteins are specific to substrate Molecule/ion binds to the receptor sited on the protein On the insides of the carrier protein, ATP binds to the protein causing it to split into ADP and a phosphate molecule, hence protein shape changes and it opens to the opposite side Molecule/ion is released as is the phosphate, which allows the protein to revert to its original shape Phosphate molecule recombined with ADP to form ATP during respiration
53
4 ways direct active transport differs from passive transport methods
Metabolic energy in the form of ATP is needed Against the concentration gradient whereas passive is down the concentration gradient Carrier proteins/pumps are needed Very selective (so is facilitated though!)
54
Explain the purpose of ATP in active transport (2 marks)
Directly moves molecules in direct active transport | Induvidually moves molecules using a concentration gradient already set up by active transport hence in co-transport.
55
Co - transport
More than one molecule is moved in the same direction by active transport
56
Sodium-Potassium Pump
Sodium ions are actively removed from cell/organelle, whilst potassium ions are actively taking in from the surroundings NOT SAME DIRECTION OF TRAVEL NOT CO-TRANSPORT
57
Use of sodium-potassium pump
Many processes including, the creation of nerve impulses.
58
Co-Transport of a glucose molecule full steps
1) Na+ ions moved out of epithelial cells, via sodium-potassium pump, which lowers intracellular concentration. 2) hence higher concentration of Na+ in blood than epithelial cell in lumen 3) Na+ ions diffuse from the lumen (cavity of ileum) into epithelial cells, down the concentration gradient. During this diffusion, glucose (or amino acids) are pulled in against glucose’s (or amino acids’) concentration gradient (in order to get the most of those molecules in the cell) 4) Glucose molecules leave the cell into blood plasma via facilitated diffusion using a third carrier protein.
59
Sodium potassium pump is — transport
Active
60
How does sodium leave the epithelial cell? | State the concentration gradient
Active transport via sodium - potassium pump | Low concentration to high concentration
61
How does glucose leave the epithelial cell? | State the concentration gradient
Via facilitated diffusion | High concentration to low concentration
62
How does sodium enter the epithelial cell? | State concentration gradient
Co - transport | High concentration to low concentration
63
How does glucose enter the epithelial cell?
Co - transport | Low concentration to high concentration
64
In the co - transport of a glucose molecule, how many proteins are used?
Three One for sodium- potassium pump One for sodium and glucose entering cell One for glucose leaving cell
65
Rate of movement improve in ileum
Microvilli on villi greatly increase SA Capillary = short diffusion distance Constant circulation of blood and constant respiration maintains the concentration gradient (higher in the ileum than blood) Active transport
66
Dilution series production
S
67
Concentration formula (osmosis)
``` V1= (C1xV2)/C2 1= stock solution 2= new solution ```

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