Mod 2 biology PMT + revision pack questions I got wrong

Why is protease an important enzyme in DNA purification

To break down proteins associated with DNA/histones

Describe how 2 polynucleotide chains are held together

• phosphodiester bonds form between nucleotides via a condensation reaction forming a sugar phosphate backbone

• Hydrogen bonding occurs between purines and pyramidines because they are different sizes. Adenine binds to thymine and cytosine binds to guanine

Explain how nitrogenous bases allows DNA identical copies to be made

• complementary base pairing and hydrogen bonding

• purine can only bind with pyramidine because they are different sizes

• One base known can pair with only one other base

Explain why only a small portion of the students mass was ATP at the end of the day

• ATP provides energy for movement e.g muscle contraction

• ATP is hydrolysed to ADP and inorganic phosphate

• ATP is constantly recycled

Differences between DNA replication and transcription

• RNA/DNA nucleotides

• Only a small section of DNA unzips in transcription

• Both strands act as a template strand in transcription

• Different helicase enzymes for both transcription and DNA replication

Explain why the process of transcription is necessary for polypeptide synthesis

• DNA is too large to leave nucleus

• DNA is transcribed to mRNA

Compare properties and functions of fibrous proteins and globular proteins in human body ( long 5 mark q)

Fibrous:

• Insoluble, long, strong, flexible

  • Collagen- provides strength in bones/ cartilage/ connective tissue

  • for protection - keratin in skin/hair/nails to give elasticity/ elastic properties

Globular:

• soluble, spherical , round in shape

• have 3D shape

• ref conjugated/ prosthetic group

• hydrophilic on outside

Functions:

• to package/ organise DNA

• hormones/receptors for cell signalling , insulin + blood glucose conc regulation

• Enzymes to catalyse reactions and lower activation energy

• fibrinogen in blood clotting

Explain the difference between the structure of a starch molecule and cellulose molecule

• Starch - alpha glucose, cellulose beta glucose

• In cellulose, the position of hydrogen and hydroxyl groups on carbon atom 1 is inverted

Explain one way in which starch molecules are adapted for their function

• compact so able to store lots of glucose molecules

• insoluble - does not affect water potential

• large - prevents diffusion out of cell

Explain how cellulose is adapted to its function in plant cells

cellulose molecules provide mechanical strength to the plant cells

They are long and unbranched

Hydrogen bonding forms fibrils

Competitive inhibitors with substrates

• Competitive inhibitor has similar shape to substrate

• Competitive inhibitor binds to active site on the enzyme so fewer enzyme substrate complexes form

Explain why water is a good solvent

Water is a polar molecule - the polarity enables it to bind to solute molecules

Describe how an enzyme such as pepsin breaks down a substrate

• Substrate is complementary to active site

• substrate fits into active site

• induced fit (FOR COMPETITIVE INHIBITORS)

• destabilising of bonds forms enzyme-product complex

• products/amino acids leave

Why was the ability of water to act as a solvent important for the survival of organisms?

• medium for metabolic reactions

• because it allows ionic compounds to separate

• organisms can absorb/take in minerals

• able to dilute toxic substances

Describe the structure of the collagen molecule

• peptide bonds between amino acids in polypeptide

• every 3rd amino acid is same/glycine

• coil/twist/spiral/helix

• three polypeptide chains

• hydrogen bonds between polypeptide chains

• crosslinks/ends of molecules being staggered

• fibrils

(ANY 3 OF THESE)

Describe three ways in which the structure of haemoglobin differs from that of collagen

• haemoglobin is globular

• Hydrophobic groups on inside/hydrophilic groups on outside

• 4 chains / sub-units/ polypeptides

• alpha helix

• subunits are two different types

Explain the shape of the substrate concentration - rate of reaction graph shown 5 mark

• more successful collisions with active site

• more ESC

• more product is formed in a given time

curve/plateau means

• most active sites are occupied

• amylase is working at Vmax

• enzymes become limiting

Suggest why the lock and key and induced fit are termed models 

Simple representation of process/structure 

Suggest how a more flexible structure might help this enzyme work faster at lower temperatures

• more bonds can form/greater surface area for contact

• easier for active site to change shape

• easier for increased chance of substrate entering active site

Suggest how the structure of the enzymes may differ in Antarctic and non-Antarctic fish

• different amino acid sequence/primary sequence

• Different tertiary structure

Suggest how the DNA of Antartic and non-Antartic fish might differ

• different base sequence

• different allele/gene 

Why loss of enzymes might be undesirable

Enzymes could have a potential/future application

Describe two functions of RER/ribosomes

• site of protein synthesis

• Folding of glycoproteins/secondary structure formation/tertiary structure formation

Virus structure

• no cytoplasm

• contains capsid

Describe how you could make a temporary mount of a piece of plant tissue to observe the position of starch grains when using an optical microscope 

1. Add a drop of water to the glass slide 

2. Obtain thin section of plant tissue and place it on the slide 

3. Stain with iodine/potassium in potassium iodide 

4. Lower cover slip using mounted needle 

Why was a TEM used to produce the image

• has high resolution

• can see internal structures of organelles

Structures that can not be seen by an optical microscope

• mitochondria

• golgi apparatus

RIBOSOMES CAN BE SEEN BY OPTICAL MICROSCOPE

One farmer concluded from the graph that feeding cows on corn reduces the omega - 3 fatty acid content in milk. Evaluate the conclusion 

• graph shows decrease with time feeding on corn 

• no control group 

• might have fallen anyway/might decrease with time rather than decrease with time spent feeding on corn 

• other factors/named factor that may have also changed 

• only one investigation so may not be representative