B3

Question 1

Where does aerobic respiration occur?

Answer 1

Aerobic respiration occurs in the mitochondria of living cells.

Question 2

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

Answer 2

1. Liver and muscle cells are using lots of energy therefore they need lots more mitochondria to provide this energy through aerobic respiration. 1. In the liver, lots of energy-demanding metabolic reactions take place. Lots of mitochondria are needed to provide that energy.2. Muscle cells need lots of energy to contract; mitochondria provide this energy.

Question 3

What are chromosomes and genes and where are they ?

Answer 3

Chromosomes are in the nucleus of cells . They are made of DNA . A section of the DNA is a gene.

Question 4

Describe the structure of DNA.

Answer 4

DNA is a double helix that contains four different bases.

Question 5

What is the genetic code and how does it control characteristics?

Answer 5

Genes contain a different sequence of bases.The genetic code controls cell activity and the production of different proteins. Each gene codes for a particular protein.

Question 6

Who discovered DNA and how did they do it?

Answer 6

Watson and Crick worked out the structure of DNA.They used data from other scientists to build a model of DNAX-rays showed that two chains were wound together to form DNA.- Data showed that bases occurred pairs.This model wasn’t accepted right away, as it was necessary for other scientists to repeat and test their work.

Question 7

Recall some examples of proteins.

Answer 7

Structural proteins - e.g. collagenHormones - e.g. insulinCarrier molecules - e.g. haemoglobinEnzymes

Question 8

What are enzymes?

Answer 8

Enzymes are protein molecules that speed up a chemical reaction.

Question 9

How do enzymes work?

Answer 9

1. The substrate molecules fit into the active site. Each substate molecule fits the active site perfectly. This is called the ‘lock and key’ mechanism.2. Enzymes are highly specific - usually only working for one substrate.3. The active site has a very specific shape; if the substrate’s shape doesn’t match the shape of the enzyme’s active site, the reaction won’t be catalysed.

Question 10

What is a gene mutation and what causes them ?

Answer 10

Gene mutations are changes to the genes.They can occur spontaneously or by radiation or chemicals. ( like the chemicals in cigarette smoke).

Question 11

What are proteins made of ?

Answer 11

Proteins are made of long chains of amino acids. Different proteins will have a different sequence of amino acids.

Question 12

Describe some jobs of proteins

Answer 12

Proteins can be enzymes, hormones, structural proteins ( eg collagen in the skin).

Question 13

What factors can change the rate of an enzyme controlled reaction?

Answer 13

A change in temperature and pH will change the rate of an enzyme-catalysed reaction

Question 14

Recall the word and symbol equation for aerobic respiration

Answer 14

Glucose + Oxygen –> Carbon dioxide + Water. C6H12O6 + 6O2 —-> 6H2O + 6CO2

Question 15

Describe examples of life processes that require energy.

Answer 15

Life processes that require energy are: movement of muscles, active transport.

Question 16

What is anaerobic respiration ?

Answer 16

Anaerobic respiration takes place during hard exercise when there is not ample oxygen for aerobic respiration. It produces lactic acid which accumulates in the muscles and causes pain and fatigue. It produces a lot less anergy than aerobic respiration.

Question 17

Write the word equation for anaerobic respiration.

Answer 17

Glucose———-> lactic acid

Question 18

Describe why during exercise breathing and pulse rates increase

Answer 18

Unicellular organisms are made of one cell and multicellular are made of more than one usually millions.

Question 19

Explain why anaerobic and aerobic respiration takes place during hard exercise.

Answer 19

Unicellular organisms are made of one cell and multicellular are made of more than one usually millions.

Question 20

Calculate respiratory quotient

Answer 20

RQ= carbon dioxide produced / oxygen used.The RQ compares the respiration rate.

Question 21

Explain the advantages of being multicellular

Answer 21

Organisms can become bigger, more complex and cells can become specialised (differentiated).

Question 22

Describe the difference between unicellular and multicellular organisms

Answer 22

Unicellular organisms are made of one cell and multicellular are made of more than one usually millions.

Question 23

How are gametes produced so that they have half the number of chromosomes?

Answer 23

They are made by a type of cell division called meiosis .

Question 24

What does the word diploid and haploid mean and what cells are examples of this?

Answer 24

Body cells are diploid and gametes are haploid . Diploid means having the normal number of chromosomes ( both chromosomes of the homologous pair) and haploid means having half ( one of the pair).

Question 25

Explain why fertilisation results in genetic variation

Answer 25

Fertilisation results in variation because each sperm and egg is genetically unique. One sperm can fertilise an egg so each fertilised egg is genetically unique.

Question 26

Explain how the structure of a sperm cell is adapted to its job

Answer 26

Sperm are adapted to be able to fertilise an egg because :1. They have a tail so they can swim towards the egg.2. They have a special cap called an acrosome so that they can digest through the outer layer of the egg .3. They have lots of mitochondria to provide the energy in respiration for the movement.

Question 27

What happens during sexual reproduction?

Answer 27

In sexual reproduction gametes ( sperm and eggs) join in fertilisation

Question 28

Describe the job of the heart

Answer 28

The heart pumps the blood around the body.

Question 29

Describe the job of cells in the blood

Answer 29

Red blood cells carry oxygen. White blood cells fight infection and platelets help in clotting the blood.

Question 30

How are cells for growth produced ?

Answer 30

Cells for growth are produced by a process called mitosis. Each cell is genetically identical .

Question 31

How do the blood vessels transport blood around the body?

Answer 31

Arteries carry blood away from the heart, veins carry blood towards the heart and capillaries are very small and take the blood to the tissues.

Question 32

Name the parts of the heart and what their function is.

Answer 32

Left and right atria receive the blood. Left and right ventricles pump the blood . Semi lunar, tricuspid and bicuspid valves prevent backflow of blood.

Question 33

How is growth of an organism measured ?

Answer 33

Growth can be measured as an increase in height, wet mass or dry mass.

Question 34

Describe the job of parts of a plant cell

Answer 34

The vacuole contains cell sap and provides support. The cell wall is made of cellulose and provides support. Chloroplasts are the site of photosynthesis.

Question 35

When cells specialise to form different types of cell , what is this called?

Answer 35

Differentiation.

Question 36

Describe the difference between animal and plant growth.

Answer 36

Animals grow in the early stages of their lives and then stop whereas plants grow continuously. Animals grow all over but plants grow at specific points called mersitems.

Question 37

Describe the process of selective breeding and state what the isuues are with it.

Answer 37

Select the desired characteristic, cross breed, select suitable offspring over many generations. Selective breeding can cause issues with health if there is inbreeding.

Question 38

What is genetic engineering ?

Answer 38

Genes can be transfererd artificially from one organism to abnother to give the desired characteristics.

Question 39

What is gene therapy?

Answer 39

Gene therapy is finding a faulty gene and artificially changing it with a working one.

Question 40

What is cloning?

Answer 40

Cloning is an example of asexual reproduction and produces genetically identical copies.

Question 41

Describe how spider plants, potatoes and strawberries reproduce asexually.

Answer 41

The parent plants produce runners with small plantles at the end . Potatoes produce underground tubers that can grow identical new plants.

Question 42

Identify simple differences between bacterial cells and plant and animal cells

Answer 42

Bacteria cells have no nucleus and no organelles like mitochondria . They are also a lot smaller than plant and animal cells.

Question 43

Where can stem cells be obtained, and what can they be used for?

Answer 43

Stem cells can be obtained from embryonic tissue and could potentially be used to treat medical conditions

Question 44

What are the advantages and risks of genetic engineering ?

Answer 44

Genetic engineering is quicker than selective breedinga nd can produce organisms with desired characteristics . Genes from other species can sometimes be added to the DNA of different species. The disadvantages of it are the unknown risks to health and the environment.Some people think it is unethical to tamper with nature.

Question 45

How do we clone animals ?

Answer 45

Take a nucleus form a body cell of the animal you wish to clone. Remove an egg cell from another animal. Remove the egg’s nucleus. Join together the empty egg cell and the original cell. Spark it with an electrical current. Grow the embryo and then implant it into a donor mother. A clone then develops and is born.

Question 46

Describe examples of genetic engineering.

Answer 46

Bacteria cells have the gene for insulin inserted in them and insulin then can be produced. Golden Rice is a strain of rice that has had a gene producing beta carotene inserted . This helps human to make vitamin A.