Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

Biology > Section 2 - Transport across cell membranes > Flashcards

Section 2 - Transport across cell membranes Flashcards

(100 cards)

Start Studying
1
Q

What is the function of glycoproteins in the cell-surface membrane?
(5 things)

A
  1. Receptors
  2. Antigens
  3. Cell signalling
  4. Receptor for hormone
  5. Cell adhesion
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

How can small, non polar substances move through membrane?

A

Pass through phospholipid bilayer

By simple diffusion

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

How can large substances move through membrane?

A

Transport
Carrier proteins
Endocytosis

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

How can polar substances move through membrane?

A

Facilitated diffusion
Channel and carrier proteins

Active transport - use of ATP

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

What is the role of membranes within cells?

A

Compartmentalisation

Reactions take place on membranes

Enzymes attached to membrane

Nuclear pore permits RNA to leave

Increases surface area of organelle

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

Why are phospholipids in the cell-surface orientated in a specific way?

A

Hydrophilic heads attracted to water

Hydrophobic tail repelled by water so they point into centre.

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

What does cholesterol within the cell-surface membrane do?

A

Add strength to the membrane
Reduce movement
Reduces fluidity

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

What is the process of co-transport?

A
  1. Sodium ions actively transported out of epithelial cells by sodium-potassium pump
  2. Low concentration of sodium ions in epithelial cell, so sodium ions diffuses down concentration gradient bringing glucose/ amino acid with it
  3. Glucose passes into blood plasma by facilitated diffusion
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

How do bacteria divide?

A

Binary fission

Replication of DNA
Division of cytoplasm

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

How does the phospholipid bilayer affect entry and exit of substances into and out of a cell?

A

Allows movement of lipid soluble/ non-polar molecules

Prevents movement of water soluble molecules

Large molecules do not move through

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What are the functions of the cell-surface membrane?

A 
Providing partially permeable barrier
Compartmentalisation
Transport of solutes
Signal transduction
Cell to cell recognition
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What are the 2 organelles without a membrane?

A

Ribosome

Centriole

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

How many nanometres wide are membranes?

A

7 nm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Why is the cell-surface membrane also known as the fluid mosaic model?

A

Fluid: individual phospholipids and proteins can move around freely within their monolayer

Mosaic: pattern produced by scattered protein molecules when the membrane is viewed from above

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is the difference between intrinsic and extrinsic proteins in the membrane?

A

Intrinsic proteins: span the bilayer and form channel/ carrier proteins

Extrinsic proteins: Found on one side of bilayer, involved in cell recognition or act to stabilise membrane

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Why are phospholipids important in the membrane?

A

Form sheets (bilayer)

Hydrophilic heads attract water

Hydrophobic tails repel water

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What is the function of the phospholipid in the membrane?

A

Allow lipid-soluble substances to enter and leave the cell

Prevent water-soluble substances entering and leaving the cell

Make the membrane flexible and self-sealing

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What is the function of proteins in the membrane?

A

Provide structural support

Act as a channels transporting water-soluble substances across

Allow active transport through carrier proteins

Form cell-surface receptors for identifying cells

Acts as receptors

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What are the functions of cholesterol in the membrane?

A

Reduce lateral movement of other molecules including phospholipids

Make membrane less fluid at high temperatures

Prevent leakage of water and dissolved ions from the cell

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Why is cholesterol important in the membrane?

A

Add strength

Limit movement of fatty acid tails by pulling them together

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What is the function of glycolipids in the membrane?

A

Act as a recognition site

Help to maintain stability of the membrane

Help cells to attach forming tissues

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What is the function of glycoproteins in the membrane?

A

Help cells to attach forming tissues

Allows cells to recognise one another

Acts as a recognition site

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What are the glycolipids in the membrane made of?

A

Carbohydrate covalently bonded to a lipid

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What are the glycoproteins in the membrane made of?

A

Carbohydrate attached to extrinsic protein

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
What is fluidity of the membrane controlled by?
Amount of cholesterol Length of fatty acid (shorter increases fluidity) Proportion of saturated and unsaturated fatty acids (Saturated decreases fluidity)
26
Why do most molecules not freely diffuse across the membrane?
Not soluble in lipids Too large to pass through Of same charge as protein channel Electrically charged (polar)
27
What is the function of the membrane in lysosmes?
Isolated harmful substances to the cell
28
What is the function of the membrane in mitochondria/ chloroplast?
Controls reaction rate Increases surface area Controls rate substances enter
29
What is the function of the membrane in nucleus?
Forms separate compartment for cells | Allows RNA out in the pores
30
What is the function of the membrane in vesicles?
Allows substances in and out of cell
31
What is the function of the membrane in cell surface?
Take up fluid and form membrane-bound vesicles
32
What is the overall function of the cell-surface membrane?
To control the movement of substances in and out of the cell
33
Which end of the phospholipid lies towards the inside of the cell-surface membrane?
Hydrophobic tail
34
What 2 properties should a drug possess if it is to enter a cell rapidly?
Lipid soluble Small in size Have no electrical charge Opposite charge of protein channel
35
What are the features of facilitated diffusion?
Passive process Down concentration gradient No energy is requires Requires channel or carrier proteins to pass through membrane
36
What are channel protiens?
Form water-filled hydrophilic channels across membrane Allow specific water-soluble ions to pass through Channels are selective, each opening to specific ion
37
What are carrier proteins?
Molecule fits into proteins Protein changes shape and molecule passes through
38
What is osmosis?
Net movement of water molecules from a region of higher water potential to a region of lower water potential across a partially permeable membrane.
39
What are 3 factors that affect the rate of diffusion?
Concentration gradient Diffusion area Thickness of exchange surface Temperature
40
What is the difference between facilitated and simple diffusion?
Facilitated only occurs at channels on the membrane where there are specific protein carrier molecules
41
Why is facilitated diffusion a passive process?
No ATP from respiration used in the process
42
Why do glucose molecules not easily pass through the phospholipid bilayer?
Only lipid-soluble substances diffuse across the phospholipid bilayer
43
What are 2 structures of the membrane that would increase the rate at which glucose is transported into a cell?
Increase in surface area | More proteins with pores
44
What is osmosis?
Net movement of water molecules from a region of higher water potential to a region of lower water potential across a partially permeable membrane.
45
If you have a high water potential, you have a...
Low solute concentration
46
If you have a low water concentration, you have a...
High solute concentration
47
Where would water move with 3 water potentials of - 400 - 600 - 200
- 200 into -400 & -600 | - 400 into -600
48
What does hypotonic mean?
Region of higher water potential (lower solute)
49
What does hypertonic mean?
Region of lower water potential (higher solute)
50
What does isotonic mean?
Region where equal water potential on either side of membrane
51
What would happen to an animal cell if it was placed in a hypotonic cell?
Water potential of cell lower than external Water enters cell by osmosis and bursts
52
What would happen to an animal cell if it was placed in a hypertonic cell?
Water potential of cell higher than external Water leaves cell by osmosis and shrinks
53
What would happen to an animal cell if it was placed in a isotonic cell?
Water potential of cell same as external Water enter/ leaves as same rate = dynamic equilibrium
54
What would happen to a plant cell if it was placed in a hypotonic cell?
As water enter turgor pressure increases, resists further entry Cell is turgid
55
What would happen to a plant cell if it was placed in a hypertonic cell?
As water leaves, membrane pulls away from cell (plasmolysis) Cell is flaccid
56
What would happen to a plant cell if it was placed in a isotonic cell?
No net movement of water Cells stays the same
57
What would happen to a plant cell if it was placed in a isotonic cell?
No net movement of water Cells stays the same
58
What is a selectively permeable membrane?
Membrane permeable to water molecules but not to larger molecules
59
Under standard conditions of pressure and temperature, what is the water potential of pure water?
Zero
60
What is active transport?
The movement of molecules into or out of a cell from a region of lower concentration to a region of higher concentration
61
What 2 things does active transport require?
ATP | Carrier proteins
62
What is the process of active transport?
1. Molecule binds to complimentary site on carrier protein 2. ATP is hydrolysed to ADP and carrier protein changes shape 3. Molecule is transported across membrane 4. One way flow as membrane can only fit into carrier protein on one side of membrane
63
What is the difference between endocytosis and exocytosis?
Endocytosis: moving large amounts in Exocytosis: moving large amount out
64
How does active transport differ from passive forms of transport?
ATP is needed Against concentration gradient Carrier proteins act as 'pumps' Selective process
65
What is one difference and one similarity between active transport and facilitated diffusion?
Similarity: both use carrier protein in plasma membrane Difference: active transport requires ATP/ occurs against concentration gradient
66
Why are many mitochondria present in cells that carry out active transport?
Mitochondria supply ATP in cells which is required for active transport to occur
67
What is the process of co-transport?
1. Na ions actively transported out epithelial cell by sodium-potassium pump into blood 2. Na ions diffuse into epithelial cell down conc. gradient through protein carrier and carries glucose with it 3. Glucose passes into blood by facilitated diffusion using carrier protein
68
How is a low concentration of sodium ions in the cell ensured in active transport?
Sodium potassium ion ATPase pump, pumps out 3 sodium in exchange for 2 potassium ions
69
What are the 3 types of co-transporter proteins?
``` Uniport = single Symport = 2 in same direction Antiport = 2 in alternate direction ```
70
What are 3 ways the rate of movement across membrane can be increased?
Increasing concentration gradient Increasing surface area Increasing density of protein channel
71
Why is the term co-transport use to describe the transport of glucose into cells?
As glucose molecules and sodium ions move into the cells coupled together
72
What are 2 similarities between the movement of substances in diffusion and osmosis?
Both move down concentration gradient Passive process Don't use energy/ ATP
73
Where in plants can cells undergoing mitosis be found?
Shoot and root tips
74
What is the mitotic index?
Ratio of cells undergoing mitosis to the total number of cells in sample
75
How do you work out mitotic index?
Mitotic index= | number of cells with visible chromosomes / number of cells in sample
76
What are the hazards and precautions needed to be taken in the mitotic index practical?
HCl = corrosive, avoid contact with skin, eye protection Blue stain = irritant, avoid contact with skin Scalpel = cut away from fingers
77
What is the purpose of calibration curves?
Used to determine concentration of unknown sample, comparing it to set of standard values with known concentrations
78
How is a calibration curve used to find concentration of plant tissue?
Plot calibration curve of percentage change in mass against concentration Find x-intercept where plant tissue is isotonic to sucrose solution
79
How would you prepare a root tip squash?
1. Use mounted needle to transfer root tips to clean microscope slide 2. Add drop of water and spread root tips with mounted needle =no overlap 3. Place another microscope slide on top, at right angles, minimising air bubbles 4. Press slides together to squash root tips and spread them out
80
What occurs when plant tissue is placed in a hypotonic solution?
Water moves into plant tissue by osmosis, plant tissue increases in mass
81
What occurs when plant tissue is placed in hypertonic soltuion?
Water moves out of plant tissue by osmosis, plant tissue decreases in mass
82
Why are potato discs left in solution for 20 minutes?
To allow time for osmosis until plant tissue reaches equilibrium with its surrounding solution
83
What is water potential determined by?
The concentration of solutes
84
Why is percentage change in mass of potato used rather than actual change in mass?
Potato chips may not all have same starting mass Percentage change allows comparison
85
What is the procedure of investigating osmosis using potato tissue?
1. Make simple dilution of 1M sucrose to produce 5 concentration. Add 5cm to 5 different test tubes. 2. Cut potato into equal sized chips and weigh 3. Place chip in each test tube and leave for 20 minutes 4. Take out and dab excess water and weigh again 5. Calculate percentage change in mass
86
What is indicated by the x-intercept of the calibration curve?
The concentration that is isotonic to solution tested
87
What does the mass of potato change after 20 minutes?
Potato chips with concentration lower than sucrose solution lose mass as there is not movement of water out of cell Potato chips with concentration higher than sucrose solution gain mass as there is net movement of water into cells
88
Why are potato chips dabbed dry after removing from the sucrose solution?
To remove any excess water clinging to its surface
89
What are the controlled variables of the potato practical?
Volume of sucrose solution Size of potato chips Length of time left in solution
90
What are 2 factors that affect permeability of cell membranes?
Temperature Concentration of solvents
91
How is beetroot used to measure permeability of cell membranes?
Higher permeability, more red pigment leaks into solution. Colorimeter used to determine absorbance
92
What is the process of investigating the effect of temperature on permeability of cell membrane?
1. Cut beetroot into 6 identical cubes 2. Place each cube in different test tube with equal volume of distilled water 3. Place each test tube into water baths at various temperatures 4. Filter each solution into cuvette and measure absorbance using colorimeter
93
What is the effect on temperature on membrane permeability?
Increasing temperature results in increase membrane permeability
94
What is the effect of ethanol concentration on membrane permeability?
Increasing ethanol concentration leads to increased membrane permeability
95
Why would placing potato in ethanol stop osmosis?
Ethanol dissolved the phospholipids
96
Why would boiling a potato piece stop osmosis?
Boiling disrupts membrane by denaturing the proteins
97
What is the sequence of events following the production of extracellular proteins that leads to their release from the cell?
Moved to golgi apparatus where they're processed Into vesicles which fuse with membrane Exocytosis
98
What are some of the roles of membranes within cells?
Compartmentalisation Nuclear pore permits RNA to leave nucleus Attachment of ribosomes
99
How can a carrier protein move glucose across a membrane by facilitated diffusion?
Glucose molecule attaches to carrier protein Protein changes shape and is released on the opposite side
100
Describe a method a student could use to prepare colour standards without using a colorimeter?
Use known concentration of blueberry juice Prepare dilution series Use colour standards for comparisons

Biology (25 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions