B1.2 What Happens In Cells

Question 1

Role and structure of DNA

Answer 1

Substance that contains instructions that determine your characteristics
Deoxyribose nuclei acid, genetic material found in the nucleus in each one of your cells

Structure:
DNA -> nucleotide -> Base -> A, C, T, G

DNA is a polymer consisting of two long strands of small units that repeat throughout the structure, called nucleotides
A nucleotide is made up of a phosphate and a base attached to the sugar
Sugar and phosphates of nucleotides form the long strands
Attraction between opposite bases holds the two strands together

Question 2

Place in size order:
Gene, chromosome, genome, DNA, nucleus, cell, nucleotide

Answer 2

Nucleotide (smallest)
Gene
DNA
Chromosome
Genome
Nucleus
Cell (largest)

Question 3

Chromosome

Answer 3

Each long polymer of DNA

Question 4

Nucleotides

Answer 4

The units that make up polymer of DNA

Question 5

Each nucleotide is made up of…

Answer 5

1 phosphate
1 deoxyribose
1 organic base
O - ⭔ - ▭
Phosphate - Deoxyribose sugar - nitrogenous base

Question 6

4 organic bases

Answer 6

Adenine (A)
Thymine (T)
Cytosine (C)
Guanine (G)

Question 7

What is a gene

Answer 7

Short section of DNA found upon a chromosome which codes for a specific protein

Question 8

Protein that DNA coils around in the formation of a chromosome

Answer 8

Histone protein

Question 9

Complementary base pairing

Answer 9

Adenine pairs with thymine
Cytosine pairs with guanine

Question 10

Name of the structure formed by DNA, discovered by Watson and Crick in 1950s

Answer 10

Double helix

Question 11

Who produced the first ever photograph of DNA, Photo 51, that lead to the discovery of DNA’s structure

Answer 11

Rosalind Franklin

Question 12

Why double helix is described as being anti parallel

Answer 12

2 strands are parallel but run in opposite directions

Question 13

Sugar phosphate backbone

Answer 13

The phosphate and deoxyribose molecules in a DNA polymer are joined
O - ⭔ - [C] ≡ [G] - ⭔ - O
/ \
O - ⭔ - [A] = [T] - ⭔ - O

Question 14

Hydrogen bonds

Answer 14

Weak bonds formed between bases of opposing strands of DNA
O - ⭔ - [C] ≡ [G] - ⭔ - O
/ \
O - ⭔ - [A] = [T] - ⭔ - O

Question 15

2 main sages of protein synthesis

Answer 15

Transcription
Translation

Question 16

Where does protein synthesis take place

Answer 16

Transcription starts in nucleus and ends where mRNA strand leaves through nuclear pore towards the ribosomes
Translation happens in cytoplasm with assistance of ribosomes

Question 17

Transcription

Answer 17

DNA unzips to allow mRNA to use it as template to make a copy of a section which codes for a specific protein
Once copied, mRNA detaches and leaves nucleus and DNA zips back up
Base T is replaced by U

Question 18

Translation

Answer 18

mRNA is read by nucleus in groups of 3 codons to produce a protein
tRNA molecules are attracted to 3 complementary bases upon mRNA bringing specific amino acids with them
These join together into a chain to form a protein

Question 19

Differences between DNA and RNA

Answer 19

DNA = Deoxynucleotides
Bases A T C G
Deoxyribose sugar
Double helix structure
Cannot leave nucleus
Long polynucleotide chain
DNA is completely protected by the body from degradation
Self replicating

RNA = Ribonucleotides
Bases A U C G - THYMINE REPLACED WITH URACIL
Ribose sugar
Single strand
Can move in and out of nucleus
Short polynucleotide chain - SHORTER THAN DNA
Strands are continually made, broken down and reused
Synthesised from DNA on an as-needed basis

Question 20

Enzymes

Answer 20

Proteins
Biological catalysts - used to speed up reactions
Can’t be used up

Question 21

What molecule do enzymes bind to

Answer 21

Substrate

Question 22

Active site

Answer 22

Part of enzyme that binds to substrate
Has specific shape which is formed by way its amino acids are folded together within protein

Question 23

Lock and key hypothesis

Answer 23

Only 1 substrate will fit into active site of 1 enzyme
They must be an exact fit

Question 24

What is formed when a substrate binds to an enzyme

Answer 24

Enzyme-substrate complex

Question 25

Factors affecting enzyme activity

Answer 25

Temperature
pH
Substrate availability / concentration
Enzyme concentration

Question 26

Effect of temperature on enzyme activity

Answer 26

Rate of reaction increases due to increased kinetic energy, meaning increased number of successful collisions
Higher temperature = faster reaction
If temperature becomes too high, enzymes denature

Question 27

Denatured

Answer 27

Structure of protein that forms enzyme has been altered due to high heat or a change in pH
Change of shape affects active site
Substrate can no longer bind to enzyme

Question 28

If an enzyme is denatured, what happens to rate of reaction

Answer 28

Enzyme can no longer catalyse the reaction
Rate of reaction decreases

Question 29

How substrate concentration affects enzyme controlled reactions

Answer 29

Higher the substrate availability, higher the rate of reaction,
until all the enzyme-substrate bases are used up

Question 30

Genotype

Answer 30

All the genes you can have (blue/brown eyes)
All combinations of alleles present in an organism

Question 31

Phenotype

Answer 31

Gene that is being expressed (brown eyes only)

Question 32

Rate of reaction

Answer 32

Rate of reaction = Amount of product formed / Time

Rate of a reaction increases if:
Temperature is increased
Concentration of a dissolved reactant is increased
Pressure of a reacting gas is increased
Solid reactants are broken into smaller pieces
A catalyst is used

Question 33

DNA database pros and cons

Answer 33

+
Check on heredity / establish family tree / find relatives
Look for genetic disorders / identify health risk factors
To choose correct medication / genomics
Confirm a person’s identity

-
Avoid being identified for a crime
Avoid high insurance costs
Remain unaware of family history / genetic disorders
Dislike of sharing personal details / privacy (reasons)