1.3 and 1.4 bio mols 2 and enzymes

Question 1

bases can either be purine or pyrimidine which are attracted by hydrogen bonds , what are they?

Answer 1

purine - 2 nitrogen containing rings. adenine, guanine in rna and DNA

pyrimidine -1 nitrogen containing rings
-thymine, cytosine in DNA
- uracil and cytosine in RNA

Question 2

what is atp?

Answer 2

a nucleotide which is a universal energy supply molecule

Question 3

how does atp release energy?

Answer 3

in a hydrolysis reaction the 3rd phosphate bond is broken, this is catalysed by ATPase enzyme, ADP is the product

Question 4

nucleic acid?

Answer 4

-polymers consisting of nucleotide monomers that carry info to make new cells

Question 5

whats a phosphodiester bond in dna?

Answer 5

bond formed between phosphate mol in one nucleotide and the sugar of another nucleotide in a condensation reaction

Question 6

how is DNA replicated? (Semi conservative)

Answer 6

1. enzyme DNA helicase unzips the DNA molecule by breaking through hydrogen bonds
2. Nucleotides line up along strands by complimentary base pairing
3. DNA polymerase joins adjacent nucleotides catalysing condensation reactions, and forming pdb
4. dna ligase joins sections of dna together, forming phosphodiester bonds. between sug and phosphates

Question 7

define a gene

Answer 7

sequence of bases on a DNA molecule coding for a sequence of amino acids in a polypeptide chain

Question 8

whats a codon/triplet

Answer 8

sequence of 3 bases of mRNA

Question 9

the genetic code is degenerate , give an adv

Answer 9

degenerate - more than one triplet can code for the same amino acid
adv - mutations occur triplets can may code for same aa. Helps maintain same protein structure

Question 10

triplet code is non - overlapping…

Answer 10

each triplet is read separately

Question 11

describe steps of transcription

Answer 11

1. DNA molecule unzips, separating dna strands
2. complimentary RNA nucleotides attach to template strand
3. phosphodiester bonds form in condensation reactions
4. rna polymerase

Question 12

describe steps of translation

Answer 12

5. ribosome attaches to mRNA
6. At each codon a molecule of tRNA with complimentary anticodons line up.
7. each tRNA has a specific amino acid binding site
8. amino acid joined by peptide bonds formed in condensation reactions

Question 13

what is the structure of enzymes ?

Answer 13

globular proteins

Question 14

explain enzyme specificity..

Answer 14

enzymes have specific shapes resulting from their tertiary and quaternary structures
-bc of this they only catalyse specific reactions

Question 15

enzymes can catalyse ..

Answer 15

intracellular reactions (reactions within cell)
extracellular reactions (reactions outside cell)

Question 16

What takes place in mutation substitution and silent

Answer 16

1. Base changes in dna
2. Mrna transcribes a diff codon
3. Codon codes for diff aa making a diff polypeptide as it’ll fold In a diff way

Question 17

What takes place in mutation deletion

Answer 17

1. Base deleted from dna, frame shift occurs
2. Deletion affects the position of start/stop codon , resulting in diff sequence of Amino acids

Question 18

What’s a mutation

Answer 18

Changes to a base sequence such as base deletions , insertions or substitutions

Question 19

Enzymes are biological catalysts

Answer 19

That speed up the rate of reaction by lowering the activation energy required

Question 20

Induced fit hypothesis?

Answer 20

Active site has distinct shape but is flexible.
Once substrate enters active site the shape of the site modifies around it forming active complex

Question 21

state the importance of miosis

Answer 21

they result in genetic variation thru independent assortment and crossing over
-halves chromosome number to produce haploid nuc so at fertalistion the no of chromosomes is restored

Question 22

2 types of genetic variation in miosis

Answer 22

crossing over (recombination) - the exchange of sections of DNA between homologous chromosomes.

independent assortment - where the chromosomes derived from female and male parent are distributed into the gametes at random

Question 23

what are chromosome mutations ?

translocation?

Answer 23

during meiosis parts of the chromosomes break off and are reattached in the wrong place

a type of cm where part of a chromosomes breaks off and joins to another chormosme

Question 24

what is non disjunction error?

Answer 24

pair of chromosomes fail to separate, during division of meiosis, resulting in one gamete w 2 copies of the chromsome and one gam with 0 copies

Question 25

how can non disjunction lead to polysomy? whats an example?

Answer 25

one gamete has 2 copies of the chromosome, after fertilisation with a normal gamete , the zygote will have polysomy (3 chro) down syndrome

Question 26

how can non disjunction lead to monosomy?

Answer 26

only one member of a pair of chromosomes is present in a cell

Question 27

what is competitive inhibition? reversible

Answer 27

when the substrate and inhibitor molecule have similar shapes to each other and both compete for the enzyme active site. preventing sub entering

Question 28

what is non competitive inhibition? reversible

Answer 28

when the inhibitor molecule binds to the allosteric site / away from as changes the shape of the active site so it cant catalyse reactions

Question 29

why is enzyme inhibition important ? what is end product inhibition?

Answer 29

to regulate metabolic pathways when the amount of end product is high it binds non competitively to an enzyme in the pathway blocking further production

Question 30

what is spermatogenesis ? what is oogenesis?

Answer 30

the creation of spermatozoa by primordial germ cells in the testes the creation of ova by primordial germ cells in the ovary

Question 31

what happens in oogenesis?

Answer 31

1. primary diploid ococyte divides by miosis to produce a big secondary haploid oocyte and a smaller polar body 2. secondary ooctye divids to produce haploid ovum and another polar body. the first polar body divides to produce 2 more

Question 32

what happens in spermatogenesis?

Answer 32

the primary diploid spermatocyte divides by miosis into 2 haploid cells called secondary spermatocytes -these each divide again so there are 4 haploid cells called spermatids -spermatids differentiate to produce sperm, which includes an acrosome etc.

Question 33

adv of sperm cells

Answer 33

contain flagellum to allow the cell to move

Question 34

summarise fertalisation

Answer 34

1. sperm cluster around 2nd oocyte 2. one sperm head touches surface , acrosome reaction triggered 3. enzymes are released by many sperm , which digest the follicle cells and jelly layer 4. head of one sperm fuses w oocyte membrane, enters cell, tail left behind 5. head absorbs water, bursts releasing chromosomes to fuse w ovums second mietoic divisio triggered after fertalisation

Question 35

prevention of polyspermy?

Answer 35

sperm cell fuses w egg cell membrane cortical granuels fuse with egg cell membrane -exyocytosis of cortical granuels happen and contents they contain are released into jelly layer of egg cell -protease enzymes cause jelly layer to thicken, fertalisation membrane

Question 36

Explain the role of the active site in the conversion of succinate to fumarate (exam q )

Answer 36

-Active site has a specific shape to fit the specific substrate succinate -lowers a.e -double bond forms between carbons - esc formed

Question 37

Explain the effect of ph on enzyme activity

Answer 37

- change in pH affect the interactions between r groups

Question 38

after fertalisation what happens

Answer 38

cleavage - mitosis without interphase blastocyst - undifferentiated ball of cells in the embryo each cell can produce any tissue

Question 39

draw out male and female gametogenesis in plants

Answer 39

.

Question 40

in male gametogenesis in plants what are the functions of the tube and generative nuclei

Answer 40

tube - has function of producing a pollen tube, which penetrates thru the ovary and down to the ovule g - divides by mitosis in the pollen tube , one of these then fuse w egg cell nucl to form offspring

Question 41

fertilisation in plants..

Answer 41

pollen grain lands on stigma. pollen tube grows from pollen grain and grows to the ovary (ovary is where embryo female sac is) -generative nucleus travels down it -g.n divides by mitosis to from 2 male nuclei

Question 42

fertlisation in plants p2

Answer 42

pollen tube fuses with embryo sac double fertalisation takes place one male nuc fuses w egg cell nuleus to produce diploid zygote other male nuc fuses w 2 polar nuclei to produce triploid endosperm nucleus

Question 43

how is tube growth achieved in plants?

Answer 43

by the production of enzymes which digest the tissue of the style making a hollow tube