B1.2 What happens in cells

Question 1

State the role of DNA in the body

Answer 1

DNA is the substance that contains all the instructions that determine your characteristics

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

What is DNA?

Answer 3

DNA is deoxyribose nucleic acid, the genetic material found within the nucleus of every one of your cells.

Question 4

Each long molecule (polymer) of DNA is a…

Answer 4

Chromosome

Question 5

The units that make up the polymer DNA are called

Answer 5

nucleotides

Question 6

Each nucleotides are composed of:

Answer 6

1 phosphate 1 deoxyribose 1 organic base

Question 7

There are four organic bases

Answer 7

Adenine Thymine Cytosine Guanine

Question 8

A gene is

Answer 8

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

Question 9

Name the protein that DNA coils around in the formation of a chromosome

Answer 9

Histone

Question 10

What it complementary base pairing?

Answer 10

Adenine always pairs with thymine Cytosine always pairs with guanine

Question 11

What is the name of the structure formed by DNA, as discovered by Watson and Crick in the 1950s

Answer 11

Double Helix

Question 12

Why is the double helix described as being ‘anti-parallel’?

Answer 12

The two strands which form DNA are parallel but run in opposite directions

Question 13

The phosphate and deoxyribose molecules in a DNA polymer are joined to form the…

Answer 13

sugar-phosphate backbone

Question 14

What is the name of the weak bonds formed between bases of opposing strands of DNA?

Answer 14

Hydrogen bonds

Question 15

Name the two main stages of protein synthesis

Answer 15

Transcription Translation

Question 16

Where does protein synthesis take place

Answer 16

Transcription - starts in the nucleus, and ends when the mRNA strand leaves through the nuclear pore to towards the ribosomes Translation - In the cytoplasm with the assistance of ribosomes

Question 17

Define transcription

Answer 17

The process by which DNA unzips to allow mRNA to use it as a template to make a copy of a section which codes for a specific protein. Once copied the mRNA detaches and leaves the nucleus and the DNA zips back up.

Question 18

Define translation.

Answer 18

The process by which mRNA is read by the nucleus in groups of three ‘codons’, to produce a protein. During translation tRNA molecules are attracted to their complementary bases upon the mRNA bringing specific amino acids with them that join together into a chain to form a protein.

Question 19

What are the key differences between DNA and RNA?

Answer 19

DNA

• Deoxyribonucleotides
• Bases: A, T, C, G
• Sugar: deoxyribose
• Double helix
• Can not leave the nucleus
• Long polynucleotide chain
• DNA is completely protected by the body from degradation.
• Self-replicating

RNA

RNA

• Ribonucleotides
• Bases: A, U, C, G
• Sugar: ribose
• Single strand
• RNA can move in and out of the nucleus.
• Short polynucleotide chain
• Strands are continually made, broken down and reused
• Synthesized from DNA on an as-needed basis.

Question 20

What are enzymes?

Answer 20

Proteins which act as biological catalysts - meaning they speed up reactions without being used up in the process.

Question 21

What is the name of the molecule that an enzyme binds to?

Answer 21

Substrate

Question 22

What is an ‘active site’?

Answer 22

An active site is part of an enzyme that binds to the substrate. It has a specific shape which is formed by the way its amino acids are folded togther within the protein.

Question 23

This hypothesis states that only one substrate will fit one enzyme, and that they must be an exact fit.

Answer 23

Lock and key hypothesis

Question 24

What is formed when a substrate binds to an enzyme

Answer 24

Enzyme-substrate complex

Question 25

State the factors affecting enzyme activity?

Answer 25

• Temperature
• pH
• Substrate availability/concentration
• Enzyme concentration

Question 26

What is the affect of temperature upon enzyme activity

Answer 26

• The rate of reaction increases as increase kintetic energy, means increased number of successful collisions.
• The higher the temperature, the faster the reaction
• If the temperature becomes too high the enzyme denatures

Question 27

What does ‘denatured’ mean?

Answer 27

• The structure of the protein that forms the enzyme has been altered due to high heat or a change in pH.
• The change in shape affects the active site
• The substrate can no longer bind with the enzyme

Question 28

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

Answer 28

As the enzyme can no longer catalyse the reaction, the rate of reaction decreases.

Question 29

How does substrate concentration affect enzyme-controlled reactions?

Answer 29

The higher the substrate availability the higher the rate of reaction until all the enzyme-substrate bases are used up.