Topic 2 Plasma Membrane & Biological Molecules

Question 1

4 main elements that make up human body are?

Answer 1

1. Oxygen
2. Carbon
3. Hydrogen
4. Nitrogen

Question 2

Function of the plasma membrane?

Answer 2

• Separates the cell from the surroundings

- controls the transport in/out of the cell

Question 3

3 major macromolecules found in the plasma membrane are?

Answer 3

1. Proteins
2. Lipids
3. Carbohydrates

Question 4

Describe the Plasma Membrane Structure

Answer 4

Lipid bilayer
Fluid mosaic model:
Fluid: lipids and proteins within the membrane move > oil consistency = better movement
Mosaic: proteins of dif types are distributed throughout the membrane lipids

Question 5

What is a chemical bond? What are 3 types of Chemical bond?

Answer 5

Link formed when atoms of REACTIVE elements combine into molecules

1. Covalent: polar & nonpolar - share e-
2. Hydrogen bonds
3. Ionic bonds - transfer of e-

Question 6

What is a covalent bond?

Answer 6

The sharing of an electron between molecules to complete the valence shell

Question 7

What is meant by organic molecule?

Answer 7

Molecule containing carbon

Question 8

What are functional groups? Provide some examples.

Answer 8

Groups of atoms on molecules that readily enter the chemical reactions to change the molecule, with hydrogen or carbon as the background atom

Ie 
Hydroxyl
Carbonyl
Carbonyl
Amino
Phosphate

Question 9

What is electronegativity?

Answer 9

Measure of an atoms attraction for the electrons it shares in a chemical bond with another atom

UNEQUAL SHARING

Question 10

Order the four most common atoms found in humans by highest electronegativity to lowest?

Answer 10

Oxygen
Nitrogen
Carbon
Hydrogen

Question 11

How is there diversity in molecules based on the initial four?

Answer 11

The way the elements bond creates diversity:
Dif lengths, patterns types of covalent bond etc

Single vs double
Position of atoms around carbon
Formation of rings - branching patterns

Question 12

Explain how water is partially charged.

Answer 12

Oxygen has ahigher pull for electrons (electronegativity) than hydrogen creating a partially negative side (near the oxygen atom) and a partially positive side (near the hydrogens)

Question 13

How is the structure of the cell membrane beneficial?

Answer 13

The Inside of t he cell is 70% water and the outside environment is also made of water so having a phospholipid bilayer with hydrophilic heads allows the cell to interact with the environment

Question 14

What is meant by polar and non-polar? What is the difference?

Answer 14

Polar: forms btwn atoms with dif electronegativity resulting in the unequal sharing of e-. Get a partial charge. hydrophilic molecules - interact with/ dissolve in water

Non polar: forms between atoms with similar electronegativities and results in equal sharing of e- hydrophobic - are excluded by water (don’t interact with water)

Question 15

What is a hydrogen bond?

Answer 15

Bond that forms Btwn positively charged hydrogen atom within a polar covalent bond in one molecule and the negatively charged atom within a polar covalent bond in another molecule.

Ie two molecules interacting because of partially positive/negative charges

Question 16

What are lipids commonly known as?

Answer 16

Fats and steroids

Question 17

What are some functions of lipids?

Answer 17

• Energy, fuel
• Insulation/protection (myelin sheath)
• Major component of membranes

Question 18

What is the typical lipid structure?

Answer 18

Carbon skeleton = hydrocarbon chain

With a functional group (hydroxyl , carboxyl)

Question 19

What is the difference between amphiphilic and amphipathic molecules?

Answer 19

In reference to phospholipids: partially hydrophobic and partially hydrophilic

Question 20

Two hydrocarbon chains attached to a glycerol would form what molecule?

Answer 20

A phospholipid

Question 21

Difference between saturated and unsaturated fatty acids

Answer 21

Saturated Fatty acid chains lack double bonds in order to hold as many hydrogen molecules as possible
H h. H
H-c-c-c-h
H.h. H

Solid at room temp due to packing of straight molecules

Unsaturated: one or more double bonds creates a bend or kink in the fatty acid means more movement means liquid at room temp

Question 22

What types of movement do the phospholipids on the cell membrane do?

Answer 22

Lateral movement occurs ~10^7 x per second

Flip flopping across the membrane is rare (about once a month) and is not spontaneous - requires energy and help from enzymes

Question 23

How does temperature effect the cell membrane?

Answer 23

Decreasing temperature= reduces fluidity

Increasing temperature- increases fluidity

Question 24

Why is fluidity increased with a temprrature rise?

Answer 24

Increase in kinetic energy results in an increase in fluidity making the membrane less stable. This creates holes where leakage occurs

Question 25

How does decreasing temperature cause a reduction in cell fluidity?

Answer 25

Slows movement down. At extreme cold temperatures the cytoplasm can freeze and ice shards will puncture the membrane creating holes where leakage can occur

Question 26

What is the “transition temperature”

Answer 26

Temperature that determines the freezing point of a cell.

Must bE above in order to function, but not high enough that the cell becomes too fluid and causing leaks

Question 27

How does does the type of phospholipid effect membrane fluidity?

Answer 27

Unsaturated phospholipids are more fluid than saturated phospholipids because of the bent shape in the leg. Creates more space between the lipids

Shorter phospholipid chains are more fluid than long chains

Question 28

How would a cell regulate its membrane fluidity in extreme temperatures?

Answer 28

By using enzymes to increase of decrease the saturation of the phospholipid and/or changing the length of the chain

Question 29

What is the natural regulator of cell fluidity and how does it work?

Answer 29

Cholesterol

Large planar molecule inserted in the bilayer and regulates fluidity.

At cold temperature - hinders solidification
High temperature - decreases fluidity, reduces ‘melting’

Question 30

What are the 3 major lipids?

Answer 30

1. Phospholipids
2. Sterols
3. Fats (triglyceride)

Question 31

What is the structure of a triglyceride and what is the function ?

Answer 31

Glycerol molecule with 3 fatty acids attached

Used for insulation and energy (myelin)

Question 32

3 cellular examples of a macromolecule are:

Answer 32

Carbohydrates
Proteins
Nucleic acids