Lecture 4-5

Question 1

What are lipids?

Answer 1

Large biological molecules that do not form polymers and are hydrophobic

Lipids include fats, phospholipids, and steroids.

Question 2

What are fats constructed from?

Answer 2

Glycerol and fatty acids

Fats are a type of lipid used for energy storage.

Question 3

Define glycerol.

Answer 3

A 3-carbon alcohol with a hydroxyl attached to each carbon.

Question 4

What are fatty acids?

Answer 4

Consist of a carboxyl group linked to a long hydrocarbon chain.

Question 5

What characterizes saturated fatty acids?

Answer 5

No double bond, solid at room temperature, most animal fats are saturated.

Question 6

What characterizes unsaturated fatty acids?

Answer 6

One or more double bonds, liquid at room temperature, found in plant and fish fats.

Question 7

What is hydrogenation?

Answer 7

The process of synthetically converting unsaturated fats to saturated fats by adding hydrogens.

Question 8

What is the major function of fat?

Answer 8

Energy storage, stored in adipose tissues.

Question 9

What are the functions of adipose tissues?

Answer 9

• Cushion vital organs
• Insulate the body

Question 10

What are phospholipids composed of?

Answer 10

Two fatty acids and a phosphate group attached to glycerol.

Question 11

What are the properties of phospholipids?

Answer 11

• Two fatty acid tails are hydrophobic
• Phosphate head group is hydrophilic

Question 12

What is the role of phospholipids in cell membranes?

Answer 12

They are the major component of the cell membrane and the most abundant lipid in plasma membranes.

Question 13

What are steroids?

Answer 13

Lipids with a carbon skeleton consisting of 4 fused rings.

Question 14

What is cholesterol’s role in cell membranes?

Answer 14

It is a component in animal cell membranes.

Question 15

What does the fluid mosaic model describe?

Answer 15

A membrane as a fluid structure with a mosaic of proteins embedded in it.

Question 16

What holds membranes together?

Answer 16

Weak hydrophobic interactions.

Question 17

What happens to most lipids and some proteins in the membrane?

Answer 17

They drift laterally.

Question 18

What did Frye and Edidin demonstrate in their experiment?

Answer 18

They labelled membrane proteins of mouse and human cells and observed hybrid cells.

Question 19

How does cholesterol affect membrane fluidity at warm temperatures?

Answer 19

It restrains movement of phospholipids, preventing the membrane from becoming too fluid.

Question 20

How does cholesterol affect membrane fluidity at cold temperatures?

Answer 20

It maintains fluidity by preventing tight packing.

Question 21

What are peripheral proteins?

Answer 21

Proteins bound to the surface of the membrane.

Question 22

What are integral proteins?

Answer 22

Proteins that penetrate the hydrophobic core and are embedded in the membrane.

Question 23

What are transmembrane proteins?

Answer 23

Integral proteins that span the membrane.

Question 24

List the six major functions of membrane proteins.

Answer 24

• Transport
• Enzymatic activity
• Signal transduction
• Cell-cell recognition
• Intercellular joining
• Attachment to the cytoskeleton and extracellular matrix

Question 25

How do cells recognize each other?

Answer 25

By binding to extracellular surface molecules containing carbohydrates.

Question 26

What does selectively permeable mean in the context of plasma membranes?

Answer 26

It regulates the molecular traffic of the cell.

Question 27

What type of molecules can easily cross the plasma membrane?

Answer 27

Hydrophobic (non-polar) molecules.

Question 28

What type of molecules do not cross the plasma membrane easily?

Answer 28

Hydrophilic (polar) molecules.

Question 29

What role do transport proteins play?

Answer 29

They allow hydrophilic substances to pass through the plasma membrane.

Question 30

What are aquaporins?

Answer 30

Transport proteins that facilitate the passage of water.

Question 31

What are carrier proteins?

Answer 31

Proteins that bind molecules and change shape to shuttle them across the membrane.

Question 32

What is diffusion?

Answer 32

The tendency for molecules to spread out evenly into available space.

Question 33

What is passive transport?

Answer 33

Diffusion of substance across a biological membrane without energy expended by the cell.

Question 34

Define osmosis.

Answer 34

Diffusion of water across a selectively permeable membrane.

Question 35

What is tonicity?

Answer 35

The ability of a surrounding solution to cause cells to gain or lose water.

Question 36

What is isotonic?

Answer 36

Solute concentration is the same as that inside the cell, resulting in no net movement across the plasma membrane.

Question 37

What is hypertonic?

Answer 37

Solute concentration is greater than that inside the cell, causing the cell to lose water.

Question 38

What is hypotonic?

Answer 38

Solute concentration is less than that inside the cell, causing the cell to gain water.

Question 39

What is osmoregulation?

Answer 39

The control of solute concentrations and water balance.

Question 40

In what type of environment do animal cells fare best?

Answer 40

Isotonic environment.

Question 41

In what type of environment are plant cells healthiest?

Answer 41

Hypotonic environment.

Question 42

What happens to plant cells in an isotonic environment?

Answer 42

They become limp due to no net movement of water (flaccid).

Question 43

What happens to plant cells in a hypertonic environment?

Answer 43

The plasma membrane pulls away from the cell wall, causing the plant to wilt (plasmolysis).

Question 44

What is facilitated diffusion?

Answer 44

Transport proteins aid the passive movement of molecules across the plasma membrane.

Question 45

What are the two types of transport proteins?

Answer 45

* Channel proteins * Carrier proteins

Question 46

What do channel proteins do?

Answer 46

Provide corridors that allow a specific molecule or ion to cross.

Question 47

What do carrier proteins do?

Answer 47

Undergo a subtle change in shape that translates the solute binding site across the membrane.

Question 48

What is active transport?

Answer 48

Moves substances against their concentration gradient and requires energy.

Question 49

What is the function of the sodium-potassium pump?

Answer 49

It is an example of active transport that helps maintain concentration gradients.

Question 50

What is membrane potential?

Answer 50

The voltage difference across a membrane.

Question 51

What creates the electrochemical gradient?

Answer 51

* Chemical force * Electrical force (effect of membrane potential on ions movement)

Question 52

What is an electrogenic pump?

Answer 52

A transport protein that generates voltage across a membrane.

Question 53

What is the main electrogenic pump in plants, fungi, and bacteria?

Answer 53

Proton pump.

Question 54

What do electrogenic pumps help store?

Answer 54

Energy that can be used for cellular work.

Question 55

What is co-transport?

Answer 55

Active transport of a solute indirectly drives transport of another solute.