Unit 1 - Membrane Proteins

Question 1

How are integral membrane proteins held within the phospholipid bilayer?

Answer 1

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

Question 2

What do integral proteins react extensively with?

Answer 2

the hydrophobic region of membrane phospholipids.

Question 3

What are some integral membrane proteins?

Answer 3

Some integral membrane proteins are
transmembrane proteins

Question 4

How are peripheral membrane proteins bound the membrane of the phospholipid bilayer?

Answer 4

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

Question 5

What is the function of the phospholipid bilayer?

Answer 5

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

Question 6

What small molecules can pass through the phospholipid bilayer by simple diffusion?

Answer 6

Some small molecules, such as oxygen and
carbon dioxide,

Question 7

How do small molecules pass through the bilayer?

Answer 7

pass through the bilayer by simple diffusion

Question 8

What is facilitated diffusion?

Answer 8

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

Question 9

To perform specialised functions what do different cell types have?

Answer 9

have different channel and
transporter proteins

Question 10

What is a feature of most channel proteins in animal and plant cells?

Answer 10

highly selective

Question 11

What are channels?

Answer 11

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

Question 12

What do channel proteins do/have?

Answer 12

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

Question 13

What are ligand gated channels?

Answer 13

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

Question 14

What are voltage-gated channels?

Answer 14

Voltage-gated channels are controlled by changes in
ion concentration

Question 15

What do transporter proteins do?

Answer 15

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

Question 16

Why do transporters alternate?

Answer 16

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.

Question 17

What is active transport?

Answer 17

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

Question 18

What are the pumps involved in active transport connected to?

Answer 18

coupled to an energy source.

Question 19

What is required for active transport to occur?

Answer 19

A source of metabolic energy is required for
active transport

Question 20

What hydrolyses ATP?

Answer 20

ATPases

Question 21

What do ATPases do?

Answer 21

Hydrolyse ATP

Question 22

Why doe some active transport proteins hydrolyse ATP directly?

Answer 22

to provide the energy for the
conformational change required to move
substances across the membrane

Question 23

What is the electrochemical gradient?

Answer 23

the concentration gradient and the electrical potential difference combine to form the electrochemical gradient

Question 24

When is the electrochemical gradient required and what does it determine?

Answer 24

It is required for a solute carrying a net charge and determines the transport of the solute.

Question 25

What is the membrane potential?

Answer 25

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

Question 26

How are ion pumps maintained?

Answer 26

use energy from the hydrolysis of ATP
to establish and maintain ion gradients

Question 27

What does the sodium-potassium pump do?

Answer 27

The sodium-potassium pump transports ions
against a steep concentration gradient using energy directly from ATP hydrolysis

Question 28

Where/how is sodium and potassium transported?

Answer 28

It actively transports sodium ions out of the
cell and potassium ions into the cell

Question 29

What is the process of the Sodium-Potassium pump?

Answer 29

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

Question 30

When an ATP molecule is hydrolysed, how many sodium’s are transported out of the cell?

Answer 30

Three sodium ions

Question 31

When an ATP molecule is hydrolysed, how many potassium ions are transported into the cell?

Answer 31

Two

Question 32

How is an electrochemical gradient established in terms of Na/K pump?

Answer 32

For each ATP hydrolysed, three sodium ions are transported out of the cell and two potassium ions are transported into the cell. This establishes both concentration gradients
and an electrical gradient.

Question 33

Where does the sodium gradient drive the active transport of glucose?

Answer 33

In the small intestine

Question 34

What happens at a glucose transporter?

Answer 34

The glucose transporter responsible for this
glucose symport transports sodium ions and glucose at the same time and in the same
direction

Question 35

What is the process of sodium and glucose symport?

Answer 35

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