Proteins in cells or cell membrane

Question 1

Membrane proteins

Answer 1

1) peripheral (loosely attached to one side surface)
2) integral (embeds inside membrane)
3) transmembrane (all the way through, both sides- this is a TYPE of integral)

Question 2

Peripheral membrane proteins are generally hydrophilic or hydrophobic?

Answer 2

Hydrophilic; held in place by H-bonding and electrostatic interaction

Question 3

How do you disrupt or detach peripheral membranes?

Answer 3

by changing salt concentration or pH.

Question 4

integral proteins are generally hydrophilic or hydrophobic?

Answer 4

hydrophobic

Question 5

How do you disrupt or detach integral membranes?

Answer 5

use detergent to destroy membrane and expose these proteins

Question 6

channel proteins

Answer 6

Provide passageway through membrane for hydrophilic (water-soluble) substances (polar, and charged)

Question 7

recognition proteins

Answer 7

Distinguish between self and foeign. They are glocoproteins (due to oligosaccharides attached). Ex: major-histocompatibility complex on macrophage

Question 8

ion channels

Answer 8

Passage of ions across membranes. Called gated channels in nerve and muscle cells, respond to stimuli. There are 3 types of gated channels: voltage, ligand, and mechanical

Question 9

Types of gated channels?

Answer 9

1) voltage-gated: respond to different in membrane potential
2) ligand-gated: chemical binds and opens channel
3) mechanical-gated: respond to pressure, vibration, temp, etc

Question 10

porins?

Answer 10

allows passage of certain ions + small polar molecules. These tend not to be specific, they’re just large passages, if you can fit you’d go through.
Ex: aquaporins

Question 11

carrier proteins

Answer 11

bind to specific molecules, protein changes shape, molecule passed across. Movement typically through integral proteins
Ex: glucose

Question 12

transport proteins

Answer 12

can use ATP to transport materials across membrane (not all use ATP)

• Active uses ATP (lower to higher concentration)
• Facilitated diffusion doesn’t use ATP, uses diffusion

Question 13

adhesion proteins

Answer 13

attach cells to neighboring cells, provide anchors for internal filaments and tubules (stability)

Question 14

receptor proteins

Answer 14

binding site for hormones + other trigger molecules

Question 15

cholesterol

Answer 15

adds rigidity to membrane of animal cells under normal conditions (but at low temperatures it maintains its fluidity)

Question 16

glycocalyx

Answer 16

a carbohydrate coat that covers the outer face of cell wall of some bacteria and outer face of plasma membrane (some animal cells). It consists of glycolipids (attached to plasma membrane) and glycoproteins (such as recognition proteins). It may provide adhesive capabilities, a barrier to infection, or markers for cell-cell recognition