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ADVANCED HIGHER BIOLOGY > UNIT 1 - KA3 > Flashcards

UNIT 1 - KA3 Flashcards

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1
Q

What is the function of the plasma membrane

A

The plasma membrane surrounds cells and controls entry and exit of materials

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2
Q

What is the fluid mosaic model

A

The fluid mosaic model describes the structure of the plasma membrane

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3
Q

What is the plasma membrane composed of

A
  • phospholipids
  • proteins
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4
Q

Phospholipid head

A

The head region of a phospholipid molecule is charged therefore hydrophilic (attracted to water)

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5
Q

Phospholipid tail

A

The tail region is uncharged and non polar therefore hydrophobic (repelled by water)

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6
Q

What gives the membrane its fluid quality

A

The phospholipids are constantly changing position this gives the membrane its fluid quality.

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7
Q

How are phospholipids arranged in the plasma membrane

A

The phospholipids are arranged into a bilayer in the plasma membrane

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8
Q

What does the hydrophobic centre of the phospholipid bilayer allow

A

The hydrophobic centre of the phospholipid bilayer allows oxygen and carbon dioxide to pass through directly by simple diffusion because they are small non polar molecules

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9
Q

How must many molecules pass through

A

Many molecules therefore must pass across the membrane with the help of proteins

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10
Q

What is the cell membrane embedded with

A

The cell membrane is embedded with protein which form a patchy mosaic

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11
Q

What are some functions of membrane proteins (5)

A
  • active transport proteins
  • Chanel forming proteins
  • enzymes
  • receptors
  • proteins for the cell cytoskeleton
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12
Q

What are the two types of protein in the plasma membrane

A

1- integral protein
2- peripheral protein

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13
Q

Where are integral proteins found

A

These are proteins found within the membrane

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14
Q

What are transmembrane integral proteins

A

Some integral proteins are transmembrane, this means that they span the entire width of the membrane

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15
Q

What are examples of transmembranes

A
  • channels
  • transporters
  • many receptors
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16
Q

What are phospholipid bilayer integral proteins held in place by

A

They are held in place by strong hydrophobic interactions with the lipid tails

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17
Q

What do regions of strong hydrophobic R groups allow

A

Regions of hydrophobic R groups allow strong hydrophobic interactions that hold integral proteins within the phospholipid bilayer

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18
Q

Where are peripheral proteins found

A

These proteins are found on the surface of the membrane

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19
Q

What kind of R groups predominate on the surface of peripheral membrane proteins

A

Hydrophilic R groups on their surface and are bound to the surface of membranes

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20
Q

What kind of interactions bind peripheral membrane proteins to the surface of the membrane / integral proteins

A

Mainly by weak ionic and hydrogen bond interactions

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21
Q

Summary of integral and peripheral

A

Integral - within membrane - hydrophobic - hydrophobic interactions
Peripheral - surface of membrane - hydrophilic - weak ionic and hydrogen bonds

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22
Q

What is the phospholipid bilayer a barrier to

A

The phospholipid bilayer is a barrier to ions and most uncharged polar molecules

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23
Q

What is facilitated diffusion

A

Facilitated diffusion is the passive transport of substances across the membrane through specific transmembrane proteins

24
Q

What do different cells have to perform specialised functions

A

To perform specialised functions, different cell types have different channel and transporter proteins

25
Q

What are the types of proteins involved in transporting substances

A

1) Channel - a) ligand gated b) voltage gated
2) transporter proteins
3) protein pumps

26
Q

What are most channel proteins in animal and plant cells

A

Most channel proteins in animal and plant cells are highly selective

27
Q

What are channels

A

Channels are multi-subunit proteins with the subunits arranged to form water-filled pores that extend across the membrane.

28
Q

Why are some channel proteins gated and change conformation

A

Some channel proteins are gated and change conformation to allow or prevent diffusion

29
Q

What are ligand gated channels controlled by

A

Ligand-gated channels are controlled by the binding of signal molecules

30
Q

What are voltage gated channels controlled by

A

voltage gated channels are controlled by changes in ion concentration

31
Q

What is a key point about gated channel proteins

A

Whilst gated-channel proteins undergo conformational change to open or close the channel. movement of molecules across the channel is dependant on the concentration gradient and the molecule is not transported across the membrane by the action of proteins

32
Q

Transporter proteins

A

Transporter proteins bind to the specific substance to be transported and undergo a conformational change to transfer the solute across the membrane

33
Q

What do transporters alternate between

A

Transporters alternate between two conformations so that the binding site for a
solute is sequentially exposed on one side of the bilayer, then the other.

34
Q

How does transporter protein differ from channel proteins

A

It differs from transport through channel proteins in that it involves a conformational change in the protein. The proteins actually pass the ions or molecules across the membrane rather than just providing a route through

35
Q

What does active transport use

A

Active transport uses pump proteins that transfer substances across the membrane against their concentration gradient

36
Q

What are pumps that mediate active transport

A

Pumps that mediate active transport are transporter proteins coupled to an energy source.

37
Q

A source of what is required for active transport

A

A source of metabolic energy is required for active transport

38
Q

What do some active transport proteins that hydrolyse atp do

A

Some active transport proteins hydrolyse ATP directly to provide the energy for the conformational change required to move substances across the membrane

39
Q

What do ATPases hydrolyse

A

ATPases hydrolyse ATP

40
Q

Describe what is meant by the term electrochemical gradient

A

For a solute carrying a net charge, the concentration gradient and the electrical potential difference combine to form the electrochemical gradient that determines the transport of the solute

41
Q

What is a membrane potential (electrical potential difference)

A

A membrane potential (an electrical potential difference) is created when there is a difference in electrical charge on the two sides of the membrane.

42
Q

How do ion pumps establish and maintain ion gradients

A

Ion pumps, such as the sodium-potassium pump, use energy from the hydrolysis of ATP to establish and maintain ion gradients

43
Q

What does the sodium-potassium pump transport

A

The sodium-potassium pump (also known as Na/K-ATPase) transports ions against a steep concentration gradient using energy directly from ATP hydrolysis

44
Q

Describe the action of the sodium - potassium pump include number of ions and directions

A

Three sodium ions are pumped out of the cell for every two potassium ions that are pumped into the cell

45
Q

2-K-IN

A

Two potassium ions pumped into the cell three sodium pumped out

46
Q

a

A

The pump has high affinity for sodium ions inside the cell therefore binding occurs

47
Q

b

A

The pump hydrolyses ATP and phosphate attaches to it. Phosphorylation by ATP causes the conformation of the protein to change

48
Q

c

A

The affinity for sodium ions decreases resulting in sodium being released outside the cell

49
Q

d

A

The pump has high affinity for potassium ions outside the cell therefore binding occurs

50
Q

f

A

Potassium ions are taken into the cell and the affinity returns to the start

51
Q

Where is the sodium-potassium found

A

The sodium-potassium pump is found in most animal cells, accounting for a high proportion of the basal metabolic rate in many organisms

52
Q

What drives the active transport of glucose in the small intestine

A

In the small intestine, the sodium gradient created by the sodium-potassium pump drives the active transport of glucose

53
Q

What does the sodium potassium pump generate in intestinal epithelial cells

A

In intestinal epithelial cells the sodium-potassium pump generates a sodium ion
gradient across the plasma membrane.

54
Q

What is the glucose transporter responsible for the active transport of glucose in the small intestine

A

The glucose transporter responsible for the active transport of glucose in the small intestine is a glucose symport protein

55
Q

What is a symporter protein

A

A symporter transports molecules across the plasma membrane at the same time and in the same direction

56
Q

Describe the action of the glucose symport protein

A

Sodium ions enter the cell down their concentration gradient and the simultaneous transport of glucose pumps glucose into the cell against its concentration gradient

ADVANCED HIGHER BIOLOGY (13 decks)

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