Exam 3 Study Guide

Question 1

What two components are cell membranes composed of?

Answer 1

Phospholipids and Proteins

Question 2

Which Component provides the cell membrane with its structure?

Answer 2

Phospholipids

Question 3

Which component provides the cell membrane with its functions?

Answer 3

Proteins

Question 4

What part of a phospholipid is hydrophobic? and Hydrophilic?

Answer 4

Tail, Head

Question 5

Sketch a phospholipid in your brain

Answer 5

2 tails, glycerol head with phosphate group attached and maybe choline or serine

Question 6

Name other lipids found in cell membranes

Answer 6

Cholesterol, Phosphoatidylserine, galactocerebroside

Question 7

Can lipid molecules exchange places with their neighbors such as flip flopping?

Answer 7

Yes but its rare bc hydrophilic heads have to cross hydrophobic tails

Question 8

More unsaturated (double) bonds in the hydrocarbon tails lead to membranes being more _________. Why?

Answer 8

Fluid because bent tails do not pack in as tightly together

Question 9

What does the inclusion of cholesterol do to the fluidity of the lipid bilayer?

Answer 9

Makes it less fluid

Question 10

The cytosolic face of a cell membranes faces ____. the non-cytosolic face of the cell membrane faces _____

Answer 10

IN, OUT

Question 11

Glycolipids tend to be found on which face of the plasma membrane?

Answer 11

Non-cytosolic face

Question 12

Transporter Proteins

Answer 12

Transport molecules (Na+ pump)

Question 13

Ion Channel Proteins

Answer 13

Act as a pore and allow ions to leave cells (K+ leak channel)

Question 14

Anchor Proteins

Answer 14

Integrins anchor cell membrane

Question 15

Receptor Proteins

Answer 15

PDGF receives signal and transmits it to the inside

Question 16

Enzyme Proteins

Answer 16

Amylase-> breaks down carbs

Question 17

Transmembrane Proteins

Answer 17

Span the length of the lipid bilayer

Question 18

Mono-layer Associated Proteins

Answer 18

Associated within one layer of the membrane

Question 19

Lipid Linked Proteins

Answer 19

Lipid is attached to protein

Question 20

Protein Attached Proteins

Answer 20

Protein attached to protein

Question 21

What are the two main classes of proteins that move molecules across the membrane?

Answer 21

Channel Proteins and Carrier Proteins

Question 22

Which proteins move substances by changing their conformation?

Answer 22

Carrier Proteins

Question 23

Which proteins move substance through pores?

Answer 23

Channel Proteins

Question 24

Where are the higher levels of Na+, K+, and Cl- in the cell?

Answer 24

K+ is in the cell, Na+ and Cl- are found outside of the cell predominately

Question 25

How do carrier proteins and channel proteins discriminate between substances to be moved?

Answer 25

Carrier proteins bind only to specific ligands
Channel proteins do this by allowing ions through of a specific size and charge

Question 26

Define passive transport. What proteins (carrier or channel) carry out passive transport?

Answer 26

Passive transport does not require the input of external energy and can only move molecules down a concentration gradient. Channels are passive, carrier proteins can be passive or active.

Question 27

Define active transport. What proteins- carrier and or channel carry out active transport?

Answer 27

Active transport requires energy input and moves molecules against a concentration gradient

Question 28

What is meant by the term “Electrochemical Gradient?”

Answer 28

Electrical forces coupled with chemical gradients

Question 29

What do we call movement of one type of molecule across the membrane? Two molecules in the same direction? Two molecules in opposite directions?

Answer 29

Uniport, Symport, and Antiport

Question 30

Describe the steps in the function of the Na+ K+ Pump. What is the result on Na+ and K+ ion concentrations and the cell membrane?

Answer 30

Na+ binds, pump phosphorylates itself hydrolyzing ATP, conformational change occurs and Na+ is ejected, K+ binds, pump dephosphorylates itself, pump returns to OG conformation and K+ is ejected

Result is High Extracellular Na+ and High Intracellular K+

Question 31

How does the electrochemical gradient affect the movement of Na+ and K+

Answer 31

Both electrical and chemical gradients want to move Na+ in. Electrical wants to move K+ in while chemical gradient wants to move K+ out

Question 32

What occurs during an action potential and the propogation of an action potential from one nerve cell to another?

Answer 32

Cell has negative resting potential because of higher concentrations of negative ions inside. High Na+ concentration outside, High K+ concentration inside. Concentration gradient wants to push K+ ions out, electrical gradient want to push K+ ions in.
Once action potential starts, Na+ voltage gated ion channels open and Na+ rushes in depolarizing local spot of membrane. Due to Na+ electrochemical gradient, Na+ rapidly rush in changing local membrane potential to positive 40 mV, switching Na+ channels to inactive state. Solwer K+ Voltage gates channels are activated by voltage change in membrane potential and K+ leaks out returning membrane to resting potential. Voltage change then switches the Na+ back to OG state and K+ channels back to closed state. Meanwhile, Na+/K+ ion pump (active carrier protein) works to return ion concentrations to OG gradients