Membrane Proteins

Question 1

What describes the structure of the plasma membrane?

Answer 1

Fluid mosaic model

Question 2

Some integral proteins are…

Answer 2

Transmembrane proteins

Question 3

What are transmembrane proteins?

Answer 3

Span entire width of the membrane e.g. channels, transporters and many receptors

Question 4

What is facilitated diffusion?

Answer 4

Passive transport of substances across the membrane through specific transmembrane proteins, used by channel and transporter proteins

Question 5

what are the proteins involved in transporting substances?

Answer 5

Channel
Transporter
Protein pumps

Question 6

Function of plasma membrane

Answer 6

Surrounds cells and controls entry and exit of materials

Question 7

Plasma membrane is composed of…

Answer 7

Phospholipids and proteins

Question 8

What gives the membrane it’s fluid quality?

Answer 8

Phospholipids are constantly changing position

Question 9

Structure of phospholipids

Answer 9

Charged, hydrophilic head and uncharged, non-polar, hydrophobic tail

Question 10

Integral proteins react extensively with…

Answer 10

hydrophobic region of membrane phospholipids

Question 11

Membrane proteins are either…

Answer 11

Integral (within membrane) or peripheral (on surface of membrane)

Question 12

How are integral proteins held within the phospholipid bilayer?

Answer 12

Regions of hydrophobic R groups allow strong hydrophobic interactions

Question 13

Peripheral proteins have…

Answer 13

Hydrophilic R groups on their surface and are bound to the surface of membranes mainly by ionic and hydrogen bond interactions

Question 14

Many peripheral proteins interact with…

Answer 14

The surface of integral proteins

Question 15

The phospholipid bilayer is a barrier to…

Answer 15

Ions and most uncharged polar molecules

Question 16

Small molecules such as oxygen and carbon dioxide can pass through membrane by…

Answer 16

Simple diffusion

Question 17

What are channel proteins?

Answer 17

Multi-subunit proteins with subunits arranged to form water filled pores that extend across membrane

Question 18

Most channel proteins in plants and animals are…

Answer 18

Highly selective

Question 19

Some channel proteins are…

Answer 19

Gated- change conformation to allow/prevent diffusion

Question 20

What are ligand-gated channels controlled by?

Answer 20

Binding of signal molecules, correct binds>gate opens>allows flow of ions through, have chemical stimulus

Question 21

What are voltage-gated channels controlled by?

Answer 21

Changes in ion concentration, have electrical stimulus

Question 22

How do transporter proteins transfer the solute across the membrane?

Answer 22

Bind to specific substance to be transported and undergo conformational change

Question 23

Transported proteins alternate between… so that…

Answer 23

2 conformations, the binding site for the solute is sequentially exposed on one side of the membrane and then the other

Question 24

What are pumps that carry out active transport?

Answer 24

Transporter proteins coupled to an energy source

Question 25

Active transport uses..

Answer 25

Pump proteins that transfer substances across the membrane against their concentration gradient so require a source of metabolic energy

Question 26

Some active transport proteins...

Answer 26

Hydrolyse ATP directly using ATPases to provide energy for the confrormational change require to move substances across the membrane

Question 27

What does the electrochemical gradient determine?

Answer 27

Transport of a solute e.g. where and how far it goes

Question 28

What is the concentration gradient?

Answer 28

Difference in concentration of a solute across the plasma membrane

Question 29

What is the electrical potential difference?

Answer 29

Created when there is a difference in electrical charge on the 2 sides of a membrane

Question 30

For a solute carrying a net charge, what combines to form the electrochemical gradient?

Answer 30

Concentration gradient and electrical potential difference

Question 31

What does the sodium-potassium pump account for?

Answer 31

A high proportion of the basal metabolic rate in many organisms

Question 32

Sodium-potassium pump actively transports...

Answer 32

3 sodium ions out and 2 potassium ions in cell (per ATP hydrolysed)

Question 33

Function of ATP hydrolysis in SPP

Answer 33

Establishes and maintains ion gradient

Question 34

Ion pumps such as the SPP transports ions...

Answer 34

Against a steep concentration gradient using energy directly from ATP hydrolysis

Question 35

How does the SPP work?

Answer 35

1. Pump has high affinity for sodium ions inside cell so binding occurs 2. Pump hydrolyses ATP and phosphate attaches (phosphorylation by ATP), conformation of protein changes 3. Affinity for sodium ions decreases so released outside cell 4. Pump has high affinity for potassium ions outside cell so binding occurs 5. Dephosphorylation causes the protein to change conformation 6. Potassium ions are taken into cell and affinity returns to start

Question 36

In intestinal epithelial cells of the small intestine, the SPP generates a...

Answer 36

sodium ion gradient across the plasma membrane, this gradient drives the active transport of glucose

Question 37

What is the protein that transports glucose called?

Answer 37

Glucose symport

Question 38

Glucose symport is responsible for...

Answer 38

The active transport of glucose and sodium ions at the same time and in the same direction.

Question 39

Sodium ions enter the cell down their concentration gradient and the simultaneous transport of...

Answer 39

Glucose pumps glucose into the cell against its concentration gradient