June wjec Unit 1 2023

Question 1

What is meant by primary structure?

Answer 1

structure of amino acids

Question 2

Secondary?

Answer 2

contains an alpha helix and beta pleated sheet

Question 3

Tertiary?

Answer 3

secondary structure folded into a 3D shape

Question 4

Cytoplasm of bacterial cellsis hypertonic to saliva and tears
suggest how the destruction of the cell wall bacteria by lysozyme results in the death by the bacteria?

Answer 4

Bacteria absorb water by osmosis
there is a higher solute potential outside of the bacteria cell compared to the inside
this creates a water potential
bacterial cells lyce due to cell wall damage

Question 5

Lysozyme works by an induced fit mechanism what does it mean?

Answer 5

the substrate changes the shape of the active site of the enzyme, allowing it to bind

Question 6

Describe + explain the effect of pH on the activity of lysozyme?

Answer 6

optimum pH for lysozyme is 5.2
changing the pH breaks the bonds that hold the enzymes shape as it is denaturing
disruption of the active site prevents the substrate binding so fewer enzyme-substrate complexes are formed

Question 7

1 advantage of lysozyme having wider pH activity than many other enzymes?

Answer 7

Lysozyme is active in a range of Ph around the body

Question 8

Metaphase of mitosis?

Answer 8

in a line of chromosomes

Question 9

Metaphase in meiosis I?

Answer 9

2 homologous pairs

Question 10

Metaphase in Meiosis II?

Answer 10

single files of 3 - reduction - half number of chromosomes in m2

Question 11

Differences in daughter cells of mitosis and meiosis?

Answer 11

Mitosis
genetically identical
6 chromosomes
diploid

Meiosis
genetically different
3 chromosomes
haploid

Question 12

Calculate the rate of distance between the centromeres of the sister chromatids between 15 and 30 minutes?

Answer 12

rate - change in y over change in x

Question 13

How does the Graoh provide evidence to show what happens in the chromosomes during anaphase of mitosis?

Answer 13

sister chromatids are pulled to the poles as the distance between the centromere increases
centromere pulled towards the spindle poles
as the distance between them and the poles decreases

Question 14

Use a scale bar to calculate magnification.

Answer 14

3.8 cm = 38 mm
38 x 1000 = 38,000/50
= x760

Question 15

Which part of the onion cells was image 2.3 taken?

Answer 15

meristem
region of growth

Question 16

What line represents oxygen?

Answer 16

straight line
diffusion

Question 17

What line represents Glucose?

Answer 17

Straight then plateaus
active transport

Question 18

Why do they have these shapes of lines?

Answer 18

glucose uses an intrinsic carrier protein as it is a polar molecule
glucose is actively transported but the rate is eventually limited by the number of carrier proteins

Oxygen passes through the phospholipid bilayer because it is non-polar
it has a linear relationship as the concentration is directly proportional to the rate

Question 19

Why can the red blood cell not make haemoglobin?

Answer 19

no golgi body as there is no post transitional modification
no DNA to code for haemoglobin
no mitochondria to make ATP for protein synthesis
no Ribosome for protein synthesis

Question 20

Why can they only transport substances across the cell membrane against a conc gradient at very low rates?

Answer 20

no mitochondria
no ATP fora active transport

Question 21

1 similarity and 1 difference between amylose + amylopectin?

Answer 21

both made of alpha glucose
amylose = straight chained whereas amylopectin is branched

Question 22

Hydrolysis def?

Answer 22

chemical insertion of water in order to break a bond

Question 23

Complete hydrolysis of starch?

Answer 23

starch is digested to maltose by amylase - carbohydrate
maltose is digested to glucose by maltase
isomaltase hydrolysis amylopectin at the 1,6 glycosidic link

Question 24

Why does this lower ratio result in an increase in the rate of starch hydrolysis?

Answer 24

more sites to be digested
and is less tightly packed
more amylopectin present

Question 25

A chemical test that shows starch is no longer present at the end of hydrolysis?

Answer 25

iodine solution
remains brown

Question 26

State the conclusion that can be made regarding the base composition of DNA?

Answer 26

there is a complementary base pairing fir all organisms
G has a very similar percentage to C and A is close to T
variation is due to experimental error

Question 27

State what is meant by semi-conservative replication.

Answer 27

Each strand acts as a template for a new strand
newly synthesised DNA molecules contain 1 old and 1 new strand

Question 28

How do these 4 bases allow the production of so many different proteins?

Answer 28

3 bases code for 1 amino acid
64 combinations of the 4 bases is 2 to the power of 6
different base sequences give rise to different amino acids sequences
different amino acid sequences as produce a wide variety of different proteins due to the removal of introns

Question 29

How to do graphs?

Answer 29

0.0 on both axis
label
but a 0 for example 90.0

Question 30

Pressure potential at incipient plasymolysis?

Answer 30

0

Question 31

How can the experiment be altered to improve?
confidence in the results
accuracy of estimated solute potential in tradescantia cells?

Answer 31

improving confidence - repeat all recordings and take more sample
smaller incremental values of the sucrose solution

Question 32

Describe the function of each of the 4 types of nucleic acid involved in protein synthesis and state where in the cell carries out the function.

Answer 32

DNA?
provides a template for the production of mRNA which provides the genetic code for the sequence of amino acids
rRNA?
to form ribosomes at the site of translation
mRNA?
synthesized in transcription and used in translation to transfer the genetic code from the nucleus to the ribosomes
tRNA?
delivers the amino acids to the site of protein synthesis

site of the function?
DNA - nucleus
RNA - cytoplasm
mRNA - cytoplasm
tRNA - cytoplasm

how tRNA activation works
ATP provides energy for the reaction
2 phosphates are released
amino acids react with ATP to form activated amino acid
amino acid is transferred to tRNA forming activated tRNA