Transport Across Membranes

Question 1

What is a cell membrane?

Answer 1

A phospholipid bilayer

Question 2

What can the cell membrane contain?

Answer 2

• Glycoproteins- Cholesterol- Transport proteins- Glycolipids

Question 3

What are transport proteins?

Answer 3

Channel and carrier proteins

Question 4

How is the phospholipid bilayer arranged?

Answer 4

• Hydrophilic heads face outwards- Hydrophobic tails face inwards

Question 5

Why is the phospholipid bilayer fluid?

Answer 5

Phospholipids can slide over each other

Question 6

What molecules can diffuse through the phospholipid bilayer?

Answer 6

Small non-polar ones e.g. CO2 and O2

Question 7

How does water cross the phospholipid bilayer?

Answer 7

Water is polar so cannot diffuse straight through the phospholipid bilayer, instead it crosses through aquaporins

Question 8

What is the role of cholesterol in the phospholipid bilayer?

Answer 8

It adds strength and support by making the membrane more rigid and less flexible. This is useful because animal cells have no cell wall and cells like haemoglobin nneed more strength as they travel alone

Question 9

How does cholesterol strengthen the membrane?

Answer 9

It binds to the hydrophobic tails

Question 10

What is diffusion?

Answer 10

The net movement of molecules from an area of high concentration to low concentration along a concentration gradient

Question 11

What type of movement is diffusion?

Answer 11

Passive

Question 12

Does diffusion require ATP?

Answer 12

No

Question 13

What are the three features that increase the rate of diffusion?

Answer 13

• Short diffusion pathway- Large surface area- Concentration gradient

Question 14

Give an example of how the body can maintain a concentration gradient?

Answer 14

• Ventilation- Circulation

Question 15

Give an example of how the body maintains short diffusion pathways

Answer 15

• Thin capillary walls

Question 16

Give examples of the body increasing surface area

Answer 16

• Villi- Microvilli- Alveoli- Cristae- Thylakoids

Question 17

How are the lungs adapted to maintain a fast rate of diffusion?

Answer 17

• Ventilation of air and circulation of the blood maintains the high concentration gradient- Alveoli and capillaries have thin walls to keep the diffusion pathway short- Alveoli and highly folded to increase the surface area

Question 18

What is facilitated diffusion?

Answer 18

The passive movement of molecules across the cell membrane via a specific transmembrane transport protein

Question 19

What molecules use carrier proteins?

Answer 19

Large molecules e.g. glucose

Question 20

What molecules use protein channels?

Answer 20

Small polar molecules like ions

Question 21

How does facilitated diffusion interact with a concentration gradient?

Answer 21

It goes along it from high to low

Question 22

What else can transmembrane transport proteins be used for?

Answer 22

Active transport

Question 23

How are the different transmembrane transport proteins different?

Answer 23

Each molecule has a specific transmembrane protein with its a specific tertiary structure

Question 24

Does active transport go with or against the concentration gradient?

Answer 24

Against

Question 25

How does active transport work?

Answer 25

Using a carrier protein and energy from ATP

Question 26

How does co-transport work?

Answer 26

Via a carrier protein which moves 2 molecules at once, one along the concentration gradient and one against the concentration gradient

Question 27

What are the 3 stages of the absorption of glucose?

Answer 27

1. Sodium-potassium pump2. Co-transport3. Facilitated diffusion

Question 28

What is the first stage of the absorption of glucose?

Answer 28

The sodium-potassium pump1. Na is pumped from the epithelial cell into the capillary against its concentration gradient therefore using energy from ATP2. K is pumped from the capillary into the epithelial cell

Question 29

What is the second stage of the absorption of glucose?

Answer 29

Co-Transport1. There is a low concentration of sodium in the epithelial cell so it enters via co-transport via a carrier protein from the lumen of the ileum2. The glucose also enters the epithelial cell from the lumen of the ileum via the same carrier protein as sodium against its concentration gradient

Question 30

What is the third stage of the absorption of glucose?

Answer 30

Facilitated Diffusion 1. Glucose is in a high concentration within the epithelial cells 2. Glucose uses a carrier protein to diffuse out of the epithelial cell into the blood where it is absorbed

Question 31

What is osmosis?

Answer 31

The passive movement of water molecules from an area of high water potential to low water potential

Question 32

What is a high water potential?

Answer 32

- High % of water - Low % of solute - Low solute concentration- Hypotonic

Question 33

What is a low water potential?

Answer 33

- Low % of water - High % of solute - High solute concentration- Hypertonic

Question 34

Water move into the roots of a plant by which process?

Answer 34

Osmosis

Question 35

In active transport using carrier proteins, what form of energy is used?

Answer 35

ATP

Question 36

What type of cells are most likely to burst when placed in a hypotonic solution?

Answer 36

Animal - no cell wall

Question 37

Within active transport, which proteins are not involved?

Answer 37

Channel

Question 38

What is a similarity between the processes of active transport and facilitated diffusion?

Answer 38

They both use a protein

Question 39

Within facilitated diffusion, which proteins are not involved?

Answer 39

Receptor

Question 40

What is a solution called which has the same water potential as the cell?

Answer 40

Isotonic

Question 41

What is a definition for water potential?

Answer 41

The likeliness of water to diffuse into or out of a solution

Question 42

If a cell is placed into a hypotonic solution, what will the net direction of water be?

Answer 42

Into the cells

Question 43

Which molecule diffuses within the process of osmosis?

Answer 43

Water

Question 44

Which of the process provides the energy for active transport to occur in humans?

Answer 44

Respiration

Question 45

Carrier proteins are involved in which processes?

Answer 45

Facilitated diffusion and active transport

Question 46

Which of molecules are able to move via simple diffusion across a cell membrane?

Answer 46

Oxygen