Membrane Proteins Flashcards

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1
Q

What are integral membrane proteins ?

A

They are proteins found in the cell membrane within the phospholipid bilayer.

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2
Q

What allow these integral proteins to hold to the phospholipid bilayer ?

A

Regions of hydrophobic R groups allow strong hydrophobic interactions that hold the proteins within the phospholipid bilayer , integral proteins interact extensively with the hydrophobic regions of the membrane phospholipids.

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3
Q

What are some integral proteins ?

A

Transmembrane proteins

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4
Q

What are peripheral membrane proteins ?

A

They are proteins which are found on the the surface of the membranes.

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5
Q

How are peripheral membrane proteins bond there ?

A

Peripheral membrane proteins have hydrophilic R groups on their surface and are bound to he surface of membranes mainly by ionic and hydrogen bond interactions .

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6
Q

What do they bind to ?

A

Many peripheral membrane proteins interact with the surfaces of integral memberane proteins .

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7
Q

What is the phospholipid bilayer?

A

It is a barrier to ions and most uncharged polar molecules

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8
Q

What can pass the phospholipid bilayer and how ?

A

Some small molecules such as oxygen and c02 can pass the bilayer by diffusion.

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9
Q

What is facilitated diffusion?

A

Is the passive transport of substances across the membrane through specific transmembrane proteins

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10
Q

How do they preform specific functions ?

A

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

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11
Q

How selective are channel proteins?

A

They are highly selective.

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12
Q

What are channels ?

A

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

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13
Q

What can some channel proteins do ?

A

Some channel proteins are gated and change confirmation to allow of prevent diffusion

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14
Q

What are ligand gated channels ?

A

Ligand-gated channels are controlled by the binding of signal molecules, when a molecule binds a gate opens and ions are allowed to flow through. and voltage- gated channels are controlled by changes in ion concentration

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15
Q

What are transporter proteins ?

A

They bind to the specific substance to be transported and undergo a confirmational change to transfer the solute across the membrane.

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16
Q

Why do transporters alternate between 2 conformations ?

A

So that the binding sight for a solute is sequentially exposed on one side of the bilayer , then on the other

17
Q

What are protein pumps ?

A

Active transport uses proteins that transfers substances across the membrane against their concentration gradient. Pumps mediate active transport are transporter proteins

18
Q

What is required for active transport ?

A

A source of metabolic energy

19
Q

What do some transport proteins hydrolyse ?

A

ATP . this directly provides the energy for the conformational change required to move the substances across the membrane.

20
Q

What hydrolyses ATP

A

ATPases

21
Q

What is an ion gradient and how is it come by ?

A

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

22
Q

What are ion pumps ?

A

Examples - sodium potassium pump

They use energy from hydrolysis of atp to establish and maintain ion gradients.

23
Q

How are membrane potentials made ?

A

When there is a difference in electrical charge and the two sides of the membrane

24
Q

What does the sodium potassium pump do ?

A

They transport ions against the concentration gradient using energy from hydrolysis

It actively transports 3 sodium’s out and 2 potassium in, This establishes both concentration gradients and an electrical gradient.

25
Q

The process of the sodium potassium pump.

A

The pump has high affinity for sodium ions inside the cell; binding occurs; phosphorylation by ATP; conformation changes; affinity for sodium ions decreases; sodium ions released outside of the cell; potassium ions bind outside the cell; dephosphorylation; conformation changes; potassium ions taken into cell; affinity returns to start

26
Q

What do sodium potassium pumps account for .

A

The sodium potassium pump is found in most animal cells and it accounts for m the basal metabolic rate in many organisms

27
Q

What happens in the small intestine

A

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

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

28
Q

What is a glucose transporter responsible for in the small intestine?

A

Active transport of glucose (glucose symport ), this transports sodium ions and glucose at the same time in the same direction

29
Q
A

Sodium goes down a gradient and simultaneous transport of glucose pumps glucose in against its concentration gradient .