B3a

Question 1

What is the mitochondria and which cell do you find it in?

Answer 1

It is in an animal cell.

Respiration occurs in the mitochondria providing energy for life processes.

Question 2

Why do liver and muscle cells have large numbers of mitochondria?

Answer 2

They need lots of energy.
Liver cells - which carry out lots of energy-demanding metabolic reactions
Muscle cells - which need energy to contract and cause movement.

Question 3

What do chromosomes in the nucleus do and what are they made of?

Answer 3

Carry coded information in the form of genes and are made of a molecule called DNA.

Question 4

What is the structure of DNA?

Answer 4

Two strands coiled to form a double helix, each strand containing chemicals called bases, of which there are four different types, with cross links between the strands formed by pairs of bases.

Question 5

What is the information in genes in the form of?

Answer 5

Coded instructions called the genetic code.

Question 6

What is the structure of chromosomes like?

Answer 6

Long, coiled molecules of DNA, divided up into regions called genes.

Question 7

What cell structure in cells is too small to be seen with a light microscope?

Answer 7

Ribosomes.

Question 8

Where are ribosomes and what are they the site of?

Answer 8

Ribosomes are in the cytoplasm and are the site of protein synthesis.

Question 9

What are the four bases of DNA?

Answer 9

A, T, C and G.

Question 10

What are the complementary base pairings?

Answer 10

A-T

G-C

Question 11

What does the genetic code do?

Answer 11

Controls cell activity and consequently some characteristics of the organism.

Question 12

What does each gene contain and code for?

Answer 12

Each gene contains a different sequence of bases and codes for a particular protein.

Question 13

How is protein structure determined by the base code?

Answer 13

Proteins are made up of chains of molecules called amino acids. each different protein has its own particular number and order of amino acids. This gives each protein a different shape, which means each protein can have a different function.

IT’S THE ORDER OF BASES IN A GENE THAT DECIDES THE ORDER OF AMINO ACIDS IN A PROTEIN.
EACH AMINO ACID IS CODED FOR BY SEQUENCE OF THREE BASES.

Question 14

What does DNA control?

Answer 14

The production of different proteins.

Question 15

Who worked out the structure of DNA first?

Answer 15

By two scientists called Watson and Crick.

Question 16

Where are proteins made and why is a copy of the gene needed?

Answer 16

Proteins are made in the cell cytoplasm by tiny structures called ribosomes. To make proteins, ribosomes use the code in the DNA.
DNA is found in the cell nucleus and can’t move out of it because it’s really big. So the cell needs to get the code from the DNA to the ribosome. This is done by using a molecule called mRNA - which is made by copying the code from DNA. The mRNA acts a messenger between the DNA and the ribosomes - it carries the code between the two.

Question 17

How did Watson and Crick use data from other scientists to build a model of DNA?

Answer 17

They used:
X-ray data showing that DNA is a double helix formed from two chains wound together.
Other data showing that the bases occurred in pairs.

Question 18

How does DNA control cell function by controlling the production of proteins?

Answer 18

The proteins produced in a cell affect how it functions. Some of them determine cell structure, others (like enzymes) control cell reactions. Different types of cell have different functions because they make different proteins. They only make certain proteins because only some of the full set of genes is used in any one cell. Some genes are ‘switched off’, which means the proteins they code for aren’t produced. The genes that are switched on determine the function of the cell.

Question 19

Why are new discoveries, such as Watson and Crick’s, not accepted or rewarded immediately?

Answer 19

Other scientists need to repeat the work first to make sure the results are reliable.