exam revision - nucleic acids & proteins

Question 1

What is a nucleotide made up of

Answer 1

nitrogenous bases
deoxyribose sugar
phosphate group

Question 2

What are the complementary base pairs

Answer 2

G-C
A-T
T-A
C-G
U-A (in mRNA)

Question 3

What is DNA replication

Answer 3

is a process whereby nucleotides are matched with complementary base pairs using enzymes to complete the process. The outcome is an identical DNA molecule of the original molecule.

Question 4

What is protein synthesis

Answer 4

protein synthesis is a two stage process that leads to the formation of specific proteins based of DNA. The process requires DNA and ribosomes.

Question 5

What are the steps of photosynthesis

Answer 5

1. Transcription

2. Translation

Question 6

What is the process of transcription

Answer 6

is the process by which the information in a DNA sequence is copied (transcribed) into a complimentary RNA sequence.
DNA unwinds using helicase, the exposed strand is copied using RNA polymerase using the base pair rule. When the mRNA iss completed it separates from the DNA and moves away. After the introns have been removed and the axons have joined together and been cap and tailed, it is ready for translation.

Question 7

What is the process of translation

Answer 7

is the process of building a polypeptide chain from amino acids, guided by the sequence of codons on the mRNA. mRNA leaves the nucleus, the mRNA joins onto a ribosome, and the nucleotide tDNA is brought into the ribosome. The anticodon bases of tRNA match with the codons of mRNA. The tRNA carries an amino acid specific for the mRNA codon. The amino acid is joined to the next amino acid, which forms a chain of amino acids.

Question 8

Helicase

Answer 8

unwinds and separates the double stranded DNA molecule

Question 9

Polymerase

Answer 9

copies the mRNA onto the DNA strand

Question 10

Lygase

Answer 10

joins neighbouring fragments together

Question 11

What is gene regulation

Answer 11

is the process of specialisation which occurs because genes within the cell can be switched on and off. This contributes to the conservation of energy and resources within the cell.

Question 12

How are genes structured

Answer 12

so that the transcription of the coding region is carefully regulated.

Question 13

What is a regulator gene

Answer 13

controls transcription, is composed of a promotor region and an operator region.

Question 14

What is a structural gene

Answer 14

is used to produce proteins, consists of axons and introns.

Question 15

what is an operator

Answer 15

a sequence of nucleotides to which a repressor can attach. The binding of the repressor will stop RNA polymerase from attaching and therefore stop transcription.

Question 16

what is a repressor

Answer 16

a protein that inhibits transcription. Binds to the operator.

Question 17

what is a promotor

Answer 17

a region of the operon where the RNA polymerase initially attaches

Question 18

What is the lock and key model

Answer 18

explains the specificity of an enzyme by describing the enzyme as a lock, and the substrate as the key. Only the right shaped key (substrate) can into the lock (active site).

Question 19

What is the induced fit model

Answer 19

explains that an active site of an enzyme has a defined shape but one with a degree of flexibility. The active site changes shape to fit tightly around the substrate and returns to its original shape in resting state.

Question 20

What is catabolism

Answer 20

cellular reactions that release useful energy from the breakdown of complex molecules

Question 21

what is anabolism

Answer 21

cellular reactions when complex molecules required by cells are synthesised from simpler building blocks, a process that requires input of energy.

Question 22

What is exergonic

Answer 22

metabolic reactions that release energy

Question 23

What is endergonic

Answer 23

reactions that require energy

Question 24

what are factors that effect enzymes

Answer 24

temperature, pH, enzyme concentration, substrate concentration

Question 25

what is inhibition of enzymes

Answer 25

cell metabolism can be controlled by regulating genes or regulating enzymes, enzymes are controlled by competitive or non competitive inhibitors

Question 26

What are competitive inhibitors

Answer 26

are compounds that resemble the substrate molecules and compete for the same active site of the enzyme. The inhibitors reduce the amount of product formed. They can be reversible or non-reversible.

Question 27

What are non-competitive inhibitors

Answer 27

are molecules that bind to a site seperate from the active site, which changes the shape of the active site. This therefore does not allow the substrate to bind to the active site