Quiz 2

Question 1

What is primary protein structure?

Answer 1

The linear sequence of amino acids in a straight line. They have an NH3 (Amino) on one end and a COO (Carboxyl) on the other.

Question 2

What is secondary protein structure?

Answer 2

The formation of a-helices or b-pleated sheets due to hydrogen bonding between the O of
a carbonyl group and the H of the amino group. B pleated sheets form when the peptide lies in a parallel or an antiparallel direction.

Question 3

What are tertiary protein structures?

Answer 3

The arrangement of the peptide chain due to interactions between R-groups gives proteins a distinct shape. These can include hydrophobic interactions,van der Waals interactions, ionic bonds, hydrogen bonds, disulphide bonds

Question 4

What are quaternary protein structures?

Answer 4

Results from the aggregation of two or more polypeptide subunits

Question 5

What can change protein functions?

Answer 5

A change in primary structure

Question 6

What determines protein structure?

Answer 6

Primary structure and physical and chemical nature can alter the structure. Alterations in pH, salt concentration, temperature or other environmental factors can cause a protein to unravel

Question 7

What is denaturation?

Answer 7

The loss of a protein’s native structure. It is now biologically inactive.

Question 8

What happens if a protein folds improperly?

Answer 8

Misfolded proteins can cause certain diseases like mad cow disease

Question 9

What are chaperonins?

Answer 9

Proteins that assist with the folding of other proteins.

Question 10

What are the steps of chaperonin actions?

Answer 10

An unfolded polypeptide enters the cylinder from one end, the cap attaches causing the cylinder to change shape to make a hydrophilic environment for folding. Then the cap come off and the properly folded protein releases

Question 11

What are nucleic acids?

Answer 11

Contain coded information for cells to transmit to future generations that determine protein production. There are two types; DNA & RNA

Question 12

What is a nucleotide made of?

Answer 12

A phosphate, sugar and nitrogenous base joined together

Question 13

What are the different sugars in DNA and RNA?

Answer 13

DNA uses deoxyribose ( OH and H on the bottom and RNA uses ribose( 2 OH at the bottom)

Question 14

What are the features of a nucleotide?

Answer 14

There’s a 5’ C phosphate group, a 1’ C base, 2 C’ OH in RNA and H in DNA, and a 3’ C OH for polymer function

Question 15

What are pyrimidines?

Answer 15

Single six-sided ring nitrogenous base, Cytosine, Thymine and uracil

Question 16

What are purines?

Answer 16

Six and Five sided rings fused, Adenine and Guanine

Question 17

What are integral membrane proteins?

Answer 17

They are embedded in the bilayer due to the protein being hydrophobic

Question 18

What are peripheral membrane proteins?

Answer 18

They are attached loosely to the surface of the membranes ( it usually interacts with the membrane proteins)

Question 19

What are glycoproteins?

Answer 19

Membrane proteins that have sugar attached, important in cell recognition

Question 20

What are glycoproteins?

Answer 20

Membrane lipids that have sugar attached

Question 21

What is cholesterol?

Answer 21

Inserted between phospholipid molecules to increase membrane fluidity and permiablity

Question 22

How do phospholipids move?

Answer 22

They move laterally or rarely flip-flip transversely

Question 23

What does high temperature do to membrane fluidity

Answer 23

It increases fluidity and permiablity since gaps in the membrane will form if the temperature goes high enough

Question 24

What happens when temperature changes in a membrane?

Answer 24

Phase change will change from solid to liquid or reverse

Question 25

The temperature at which phase transition occurs depends on?

Answer 25

The length of the fatty acid Long=Solid, Short=Liquid. Shape; Saturated=solid, Unsaturated=liquid.Cholesterol acts as a fluidity buffer to maintain membrane fluidity at differing temperatures since it interferes with lateral movement and also prevents the packing of phospholipids at cooler temperatures.

Question 26

What are the six major functions of membrane proteins?

Answer 26

Transport of molecules into or out of the cell, enzymatic reactions near the membrane, signalling via receptors, cell-cell recognition, intercellular attachment, attachment of the cell to extracellular matrix proteins

Question 27

What are the three ways of transport in membranes?

Answer 27

Diffusion facilitated diffusion and active transport.

Question 28

What is diffusion?

Answer 28

It occurs best with small hydrophobic molecules that are soluble in the bilayer and they spread out until equilibrium is reached. Uncharged can rarely pass through and charged never can.

Question 29

What is osmotic lysis?

Answer 29

An influx of water in animal cells from an outside hypotonic solution

Question 30

What is plasmolysis?

Answer 30

When a turgid (normal) plant cell shrivels and the membrane pulls away from the cell wall from a hypertonic solution and becomes plasmolyzed

Question 31

What is facilitated diffusion?

Answer 31

When specific molecules are impeded by the membrane but are transported by specific proteins. Channel proteins only allow one type of molecule or ion to pass through, channel proteins are gated and can be turned on by specific stimulus. Carrier proteins undergo a slight change in shape to translocate a solute across the membrane, it can move in any direction but always down the concentraion gradient.

Question 32

What is active transport?

Answer 32

It is used to move a substance against the concentration gradient, which is needed to; concentrate nutrients in the cells, expel waste, and establish voltage/chemical gradients, all these proteins are carrier proteins which are specific.

Question 33

How do animals maintain a high internal concentration of K and NA?

Answer 33

A Sodium and potassium pump and a stored energy molecule called ATP ( Adenosine triphosphate, it breaks apart and releases energy)

Question 34

What are the steps of active transport?

Answer 34

Cytoplasmic Na binds to the pump, which stimulates phosphorylation by ATP, this causes the protein to change shape expelling Na to the outside, K+ binds on the extracellular side and triggers the release of the phosphate group, loss of phosphate restores the protein’s original shape, K+ is released and the cycle repeats. 3 Na+ (in) + 2 K+ Start (out) + ATP
End 3 Na+ (out) + 2 K+ (in) + ADP + Pi this creates a more negtaive inside than outside which is membrane potential.

Question 35

What forces drive diffusion?

Answer 35

A difference in concentration (chemical force), a difference in total charge (electrical force) which is the electrochemical gradient. Charged molecules flow down the electrochemical gradient.

Question 36

What do electrogenic pumps do?

Answer 36

Create electrochemical gradients. Animals use K Na+ pump and plants use proton pumps.

Question 37

What are cotransporters?

Answer 37

Couple the “downhill” transport of a solute to the “uphill” transport of a second substance against its own concentration gradient