Membrane Transport-Lecture 2 Exam 1

Question 1

Describe the structure of the plasma (cell) membrane, including its composition and arrangement of lipids, proteins, and carbohydrates

Answer 1

Primarily composed of a phospholipid bilayer, with embedded proteins and attached carbohydrates, forming a fluid mosaic structure where components can move freely within the membrane

Question 2

Describe the functions of different membrane transport proteins

Answer 2

-Channel Proteins: cylinder-shape allows for the passage of water, ions, and some molecules
-Carrier Proteins: undergo a conformational change to “carry” substances across the membrane

Question 3

Carrier Proteins Transport Directions

Answer 3

• Uniport: transport 1 substrate
• Symport: transport 2 or more substrates in the same direction
• Antiport: transport substrates in the opposite direction

Question 4

Simple Diffusion

Answer 4

-Mechanism: molecules diffuse from high to low concentration through the phospholipid bilayer
-Materials Moved: small and/or non-polar molecules such as water, oxygen, carbon dioxide, etc.
-Transport Proteins Involved: none -Concentration Gradient: passive transport concentration gradient (high to low)

Question 5

Facilitated Diffusion

Answer 5

-Mechanism: uses membrane proteins to transport molecules across the membrane
-Materials moved: carbohydrates (polar or large molecules)
-Transport Proteins Involved: channel/carrier
-Concentration Gradient: moving down

Question 6

Primary Active Transport

Answer 6

-Mechanism: directly uses chemical energy to transport all species of solutes across a membrane
-Materials moved: Sodium(Na+) & Potassium(K+), etc.
-Transport Proteins Involved: carrier(Na+-K+ pumps)
-Concentration Gradient: against gradient (low to high)

Question 7

Secondary Active Transport

Answer 7

-Mechanism: uses potential energy stored in concentration
gradients as an “energy source”
-Materials moved: Na+ ions, glucose, amino acids, etc.
-Transport Proteins Involved: carrier(antiport & symport)
-Concentration Gradient: created by active transport(ATP)

Question 8

Sodium/Potassium ATP Pump

Answer 8

LOOK AT NOTES!!!

Question 9

Define phosphorylation of a transport protein and describe the role this process plays in active transport

Answer 9

The chemical process where a phosphate group is added to a specific amino acid residue on a transport protein, which often results in a conformational change in the protein, allowing it to actively move molecules across a cell membrane against their concentration gradient by changing its binding affinity for the transported molecule

Question 10

Define dephosphorylation of a transport protein and describe the role this process plays in active transport

Answer 10

The removal of a phosphate group from a transport protein molecule, which is a crucial step in the cycle of active transport, often causing a conformational change in the protein that allows it to switch between states

Question 11

Properties of Protein Carrier-Mediated Transport and Describe how they influence transport across a membrane

Answer 11

-Specificity: A carrier protein can only bind and transport a specific molecule or similar group of molecules
-Competition: Different molecules may “compete” for binding sites on carrier proteins; Competitive inhibitors bind to the carrier protein and prevents the transport of the intended molecule