Cell Membrane and its Functions

Question 1

Functions of the Membrane

Answer 1

• Physical barrier
• Gateway for exchange
• Communication
• Structure

Question 2

What is it Made of?

Answer 2

-Phospholipids with a choline head and a fatty acid tail
-Cholesterol

Question 3

Glycocalyx

Answer 3

• Glycolipids and glycoproteins on the surface of the cell
• Cell identity and orientation

Question 4

Diffusion

Answer 4

-Movement of particles down their concentration gradient
-Membrane diffusion is used for small molecules like 02 and CO2, and steroids

Question 4

Permeability

Answer 4

• Permeable to small molecules
• Transmembrane Proteins for polar particles
• Macromolecules are transported via vesicles

Question 5

Osmosis

Answer 5

• Water is pulled along by diffusible molecules or ions across a membrane

Question 6

Tonicity

Answer 6

-Isotonic = same number of diffusible particles on both sides of the membrane, So same amount of water
-Hypertonic =more diffusible particles outside the cell, so water rushes out (crenation)
- Hypotonic =more diffusible particles inside the cell, so water rushes in (hemolysis)

Question 7

Channel Mediate Facilitated Diffusion

Answer 7

-Proteins are used as non-selective channels for ions to pass through
- follows the concentration gradient
-Eg. Na or k channel
- Molecule does not bind to channel

Question 8

Carrier Mediated Facilitated Diffusion

Answer 8

• Product entering the cell binds to a membrane protein and enters the cell
  -No ATP required
  -Powered by concentration gradient

Question 9

Active Transport

Answer 9

-Works against the concentration gradient
- ATP required
-Carrier protein required

Question 10

Primary Active Transport

Answer 10

• Product binds to carrier protein
• 1 ATP used to power the protein

Question 11

Cotransport Mechanism/Symporter

Answer 11

• One product is following its gradient while the other is going against
• Both products bind to the carrier protein and as one enters naturally the other will follow with it

Question 12

Counter Transport/Antiporter

Answer 12

• same concept as cotransport but as one product enters, the other leaves

Question 13

Vesicle Transport

Answer 13

• Endocytosis and exocytosis
  -Vesicles made of phospholipids merge with the cell wall in order to transport large molecules

Question 14

Receptor Mediated Endocytosis

Answer 14

-Particles bind to receptors on the outside of the cell and are taken in as vesicles
-Ex transport of lipids into the cell

Question 15

Phagocytosis

Answer 15

• Products entering a phagocyte to be destroyed

Question 16

Pinocytosis

Answer 16

• Moving water into the cell

Question 17

Epithelial Transport

Answer 17

• Combines diffusion and active transport
• Happens most in the gut and kidneys

Question 18

Ligands

Answer 18

Molecules that bind to other cells for communication, such as hormones and neurotransmitters

Question 19

Channel Linked Receptors

Answer 19

• Neurotransmitters bind to ion channels in order to open them
• Ions are allowed into the cell
• Electrify nerve and muscle cells

Question 20

Enzymatic Receptors

Answer 20

• Nothing moves in or out of the cell
• Ligand binds to an inactive receptor attached to a protein kinase enzyme, activating it
• Receptor directly activates a protein kinase
• Kinase phosphorylates another enzyme causing it to turn on or off

Question 21

G-Protein Coupled Receptors

Answer 21

• Indirectly activates protein kinase enzymes
• Ligand binds to an inactive receptor, activating it
• G-protein attaches itself to the receptor, becoming active
• Active G-protein activates an effector protein

Question 22

Second Messenger Response

Answer 22

• Activated effector protein makes a secondary messenger available within the cell
• Secondary messenger activates a protein kinase
• Active kinase phosphorylates other enzymes

Question 23

cAMP, Calmodulin, Calcium

Answer 23

Three types of secondary messengers