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AQA AS Biology > Transport Across Membranes > Flashcards

Transport Across Membranes Flashcards

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1
Q

What is a cell membrane?

A

A phospholipid bilayer

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2
Q

What can the cell membrane contain?

A
  • Glycoproteins- Cholesterol- Transport proteins- Glycolipids
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3
Q

What are transport proteins?

A

Channel and carrier proteins

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4
Q

How is the phospholipid bilayer arranged?

A
  • Hydrophilic heads face outwards- Hydrophobic tails face inwards
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5
Q

Why is the phospholipid bilayer fluid?

A

Phospholipids can slide over each other

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6
Q

What molecules can diffuse through the phospholipid bilayer?

A

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

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7
Q

How does water cross the phospholipid bilayer?

A

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

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8
Q

What is the role of cholesterol in the phospholipid bilayer?

A

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

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9
Q

How does cholesterol strengthen the membrane?

A

It binds to the hydrophobic tails

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10
Q

What is diffusion?

A

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

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11
Q

What type of movement is diffusion?

A

Passive

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12
Q

Does diffusion require ATP?

A

No

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13
Q

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

A
  • Short diffusion pathway- Large surface area- Concentration gradient
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14
Q

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

A
  • Ventilation- Circulation
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15
Q

Give an example of how the body maintains short diffusion pathways

A
  • Thin capillary walls
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16
Q

Give examples of the body increasing surface area

A
  • Villi- Microvilli- Alveoli- Cristae- Thylakoids
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17
Q

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

A
  • 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
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18
Q

What is facilitated diffusion?

A

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

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19
Q

What molecules use carrier proteins?

A

Large molecules e.g. glucose

20
Q

What molecules use protein channels?

A

Small polar molecules like ions

21
Q

How does facilitated diffusion interact with a concentration gradient?

A

It goes along it from high to low

22
Q

What else can transmembrane transport proteins be used for?

A

Active transport

23
Q

How are the different transmembrane transport proteins different?

A

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

24
Q

Does active transport go with or against the concentration gradient?

A

Against

25
Q

How does active transport work?

A

Using a carrier protein and energy from ATP

26
Q

How does co-transport work?

A

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

27
Q

What are the 3 stages of the absorption of glucose?

A
  1. Sodium-potassium pump2. Co-transport3. Facilitated diffusion
28
Q

What is the first stage of the absorption of glucose?

A

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

29
Q

What is the second stage of the absorption of glucose?

A

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

30
Q

What is the third stage of the absorption of glucose?

A

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

31
Q

What is osmosis?

A

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

32
Q

What is a high water potential?

A
  • High % of water - Low % of solute - Low solute concentration- Hypotonic
33
Q

What is a low water potential?

A
  • Low % of water - High % of solute - High solute concentration- Hypertonic
34
Q

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

A

Osmosis

35
Q

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

A

ATP

36
Q

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

A

Animal - no cell wall

37
Q

Within active transport, which proteins are not involved?

A

Channel

38
Q

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

A

They both use a protein

39
Q

Within facilitated diffusion, which proteins are not involved?

A

Receptor

40
Q

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

A

Isotonic

41
Q

What is a definition for water potential?

A

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

42
Q

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

A

Into the cells

43
Q

Which molecule diffuses within the process of osmosis?

A

Water

44
Q

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

A

Respiration

45
Q

Carrier proteins are involved in which processes?

A

Facilitated diffusion and active transport

46
Q

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

A

Oxygen

AQA AS Biology (18 decks)

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