The building blocks of cells

Question 1

Describe the function of the components of a bacterial cell

Answer 1

1) chromosomal dna - carries most of the bacterial genes
2) plasmid dna - contain additional genes that are not found in chromosomes
3) flagellum - to help them move
4) cell wall - for protection, made of different substances to plant cell walls.

Question 2

Describe the function of the components of a plant cell

including chloroplast, large vacuole, cell wall, cell membrane, mitochondria, cytoplasm and nucleus

Answer 2

> cell membrane - controls what enters and leaves the cell
nucleus - large structure that contains DNA - instructions for the building and working of the cell
cytoplasm - jelly-like substance that fills the cell - many reactions take place here
mitochondria - tiny structures where respiration takes place releasing energy for cell processes
cell wall - made of cellulose, and it is tough so that it helps support the cell and helps it keep it shape
chloroplast - structures where photosynthesis takes place to make food for the plant cell
central vacuole contains cell sap, which helps keep the plant rigid

Question 3

Describe the function of the components of an animal cell

including cell membrane, mitochondria, cytoplasm and nucleus

Answer 3

> cell membrane - controls what enters and leaves the cell
nucleus - large structure that contains DNA - instructions for the building and working of the cell
cytoplasm - jelly-like substance that fills the cell - many reactions take place here
mitochondria - tiny structures where respiration takes place releasing energy for cell processes

Question 4

Describe how plant and animal cells can be studied in greater detail with a light microscope

Answer 4

light microscope uses light to magnify objects. the greatest possible magnification using a light microscope is about *2000

Question 5

how changes in microscope technology have enabled us to see cells with more clarity and detail than in the past

Answer 5

magnification enables us to see plant cells, animal cells an bacterial cells, and the structure inside them.

Question 6

magnification formula

Answer 6

magnification of object = magnification of eyepiece * magnification of objective

Question 7

what is a gene

Answer 7

gene is a section of a molecule of DNA and that it codes for a specific protein

Question 8

Describe a DNA molecule

Answer 8

DNA is a long, coiled molecule formed from two strands. the strands are twisted in a double helix. the two strands of the double helix are joined by pairs of bases. there are four different bases in DNA: A(adenine), T(thymine), C(cytosine), G(guanine). A always pairs with T, C always pairs with G. weak hydrogen bond’s between the base pairs hold the DNA strands together

Question 9

how to extract DNA from cells

Answer 9

1) kiwi fruit is mashed up and mixed with salty water and detergent. breaking open the cells and helps to release the DNA from the nuclei.
2) protease enzyme is added to the filtered mixture. the enzyme helps to break up proteins in cell membrane and so release more DNA
3) ice-cold ethanol is poured carefully down inside the tube into the mixture. the ethanol makes the DNA separate from the liquid so it is easy to lift out

Question 10

Explain how the structure of DNA was discovered, including the roles of the scientists Watson, Crick, Franklin and Wilkins

Answer 10

wilkins and franklin studied the structure of DNA using X-rays. Franklin studied X-ray photographs of DNA to work out how the atoms were grouped. watson and crick interpreted data from other scientists in their study of DNA structure. Franklins photographs were the final clue that helped them build the double helix model

Question 11

describe the process of genetic engineering.

Answer 11

1) a gene is cut out of a human chromosome using enzymes
2) a DNA plasmid is taken out of a bacterium and cut open using enzymes.
3) the human gene and the plasmid are mixed together.
4) the human gene and the plasmid are stuck together to make a new plasmid.
4) the new plasmid with the human insulin gene is put back into a bacterium. the bacterium has been genetically modified.

Question 12

Discuss the advantages and disadvantages of genetic

engineering to produce GM organisms

Answer 12

A) making bacteria insulin using GM bacteria is quicker and cheaper than producing it any other way. so more people with diabetes can be treated.
D) a few diabetic people react badly to this insulin and need a different form
A) golden rice is a GM plant that contains genes from other plants that increases the production of beta-carotene. Beta-carotene makes Vitamin A. it could prevent illness caused by lack of vitamin A in people who mainly eat rice
D) golden rice seed costs more than normal rice seed, so the poorest people cant afford to grow it

Question 13

Describe the division of a cell by mitosis

Answer 13

the parent diploid cell, which has two sets of chromosomes, copies each chromosome exactly. when the cell divides in two, each cell gets one copy of each chromosome. the daughter cells are genetically identical to each other and the parent cells. they are also diploid cells

Question 14

when does mitosis occur

Answer 14

mitosis occurs during growth, repair and asexual reproduction

Question 15

what happens at fertilisation

Answer 15

haploid gametes combine to form a diploid zygote

Question 16

Describe the division of a cell by meiosis

Answer 16

the parent cell is a diploid cell. it has two sets of chromosomes. the parent cell divides in two and then in two again. four daughter cells are produced. before the parent cell divides each chromosome is copied. each daughter cell gets a copy of one chromosome from each pair. each daughter cell has only one set of chromosomes. so these are haploid cells. the daughter cells are not all identical - meiosis results in variation .

Question 17

what is cloning

Answer 17

cloning is an example of asexual reproduction that produces genetically identical copies

Question 18

Demonstrate an understanding of the stages in the

production of cloned mammals

Answer 18

a) removal of diploid nucleus from a body cell
b) nucleus removed from egg cell
c) insertion of diploid nucleus into empty egg cell. the cell is then stimulated with an electric pulse to start mitotic division.
d) cell is stimulated with an electric pulse to start mitotic division
e) cell divides and grows as embryo
f) embryo is placed in the uterus of a surrogate mother until it is ready to be born
g) the surrogate mother is a different animal form the donors of the body cell and egg cell.

Question 19

the advantages, disadvantages

and risks of cloning mammals

Answer 19

A) if animal that is cloned has good features, all of its offspring will have the same good features
D) more difficult to clone a mammal than a plant. it may take many attempts before a healthy cloned mammal is born, and each attempt costs more money
D) cloned mammals may suffer more health problems than usual, which may cause them to die early
D) any genetic defect will be passed on to offspring

Question 20

describe how embryonic stem cells change as an animal matures

Answer 20

stem cells in the embryo can differentiate into all other types of cells, but that cells lose this ability as the animal matures

Question 21

the advantages, disadvantages and risks arising from adult and embryonic stem cell research

Answer 21

embryonic
A) easy to extract from embryo
A) produce any type of cell
A) replaces fault cell with healthy cell
D) embryo destroyed when cells removed. some people think embryos have a right to life
D) body recognises the cells as different and will reject them without use of drugs.
I) may produce cancer cells instead of healthy cells
adult stem cells
A) no embryo destroyed so not an ethical issue
A) if taken from the person to be rejectyed, will not cause rejection by the body
D) difficult to find and extract from tissue
D) produce only a few types of cell

Question 22

Demonstrate an understanding of how gene mutations change the DNA base sequence and that mutations can be harmful, beneficial or neither

Answer 22

a mutation can change one or more of the bases in the DNA base sequence. this may change the amino acid that is added to the chain during translation of the ribosome. a change in amino acid may:
> have no effect if it doesn’t change the shape of the protein or the way it works
> be beneficial if it helps the protein to work better than before
> be harmful if the protein changes shape and does not work so well. an example is sickle cell disease

Question 23

Describe enzymes

Answer 23

enzymes are biological catalysts

Question 24

are enzymes specific?

Answer 24

enzymes are highly specific for their substrate, because only a substrate with the right shape can fit into the active site.

Question 25

Demonstrate an understanding of the action of enzymes in terms of the ‘lock-and-key’ hypothesis

Answer 25

the lock and key describes the way that the substrate fits like a key into the active site.

Question 26

Describe how enzymes can be denatured due to changes in the shape of the active site

Answer 26

at very high temperatures the active site breaks up and the enzyme is denatured

Question 27

define active site and explain its role

Answer 27

the active site matches the shape of the substrate molecules and holds them together so bonds can for between them to make the product