Must revise paper 3 apparently

Question 1

What are the 5 key properties of water?

Answer 1

• Important metabolite
• Important solvent
• High specific heat capacity
• High specific latent heat
• Cohesion and Adhesion

Question 2

Why is water an important metabolite?

Answer 2

• It is present within hydrolysis or condensation.

Question 3

Why is water an important solvent?

Answer 3

• Water is a polar molecule and can therefore interact with other charged ions or polar molecules.

Question 4

Why does water have a relatively high specific heat capacity?

Answer 4

• Due to hydrogen bonding, it takes a lot of energy to change the temperature of water.

Question 5

Why does water have a large latent heat of vaporisation?

Answer 5

• It takes a lot of energy to break hydrogen bonds and change liquid water into a gas.

Question 6

Why is water very cohesive and adhesive?

Answer 6

• Water is cohesive as water forms hydrogen bonds with itself.
• Water is adhesive as water forms hydrogen bonds with other materials.

Question 7

Why is water being a good solvent useful?

Answer 7

• Many ions and molecules can dissolve in it.
• Provides a stable environment for aqueous organisms.

Question 8

Why is water having a high specific heat capacity important?

Answer 8

• Water doesn’t experience rapid changes in temperature and acts as a buffer to sudden changes in temperature.

Question 9

How do aquatic and terrestrial organisms benefit from a high specific heat capacity?

Answer 9

Aquatic - Can live in a thermally-stable environment where their enzymes can stay at optimum temperature.
Terrestrial - Can maintain a constant body temperature.

Question 10

Why is having a large latent heat of vaporisation?

Answer 10

• Allows water to be an excellent coolant.

Question 11

Why is cohesion and adhesion important?

Answer 11

• Cohesion allows water to create surface tension when in contant with the air.
• E.G sweat forming droplets which evaporate to cool an organism.

Question 12

Overall Exam Question:
Explain five properties that make water important for organisms.

Answer 12

1) Water has a high latent heat of vaporisation providing a cooling effect.
2) Water has a high specific heat capacity allowing the buffering of temperature.
3) Water is a good solvent allowing metabolic reactions to occur.
4) Water is a good metabolite, being essential in condensation and hydrolysis reactions.
5) Water has strong cohesion which supports columns of water in plants.

Question 13

What is the special term for an ATP molecule?

Answer 13

A nucleotide derivative (A modified form of a nucleotide)

Question 14

What is the structure of ATP?

Answer 14

Adenine, Three phosphates and a ribose sugar.

Question 15

How is ATP produced?

Answer 15

• The condensation reaction between ADP and Pi via the catalyst ATP synthase.

Question 16

How does ATP act in the body once formed?

Answer 16

• ATP diffuses to parts of the cell that requires the most amount of energy.
• ATP is then hydrolyses into ADP and Pi via ATP hydrolase.

Question 17

What are 3 key points about ATP as an energy source?

Answer 17

1) ATP is an immediate energy source but not a long term energy source because of its unstable bonds.
2) ATP releases less energy than glucose allowing energy to be released in smaller, more manageable quantities.
3) ATP cannot be stored.

Question 19

What is the role of DNA and RNA?

Answer 19

DNA - holds genetic information in all living organism.
RNA - Transfers genetic information from DNA to ribosomes

Question 20

What are DNA molecules called?

Answer 20

Polynucleotides

Question 21

What are the components of DNA and RNA?

Answer 21

Phosphate group, nitrogenous base, ribose sugar

Question 22

What are the base pairings for DNA and RNA?

Answer 22

DNA - A-T C-G
RNA - A-U C-G

Question 23

How are polynucleotides joined together?

Answer 23

Condensation reaction between two nucleotides that forms a phosphodiester bond.

Question 24

What are the bonds that join nucleotides together?

Answer 24

Phosphodiester bonds

Question 25

What is the chain of sugars and phosphates called?

Answer 25

Sugar-phosphate backbone

Question 26

What direction do DNA strands move?

Answer 26

- Anti parallel direction

Question 27

How does the structure of DNA link to its function?

Answer 27

1) Weak hydrogen bonds between 2 DNA polynucleotides can separate easily during DNA replication. 2) DNA is a very large molecule, so can carry lots of genetic information. 3) Base pairs are protected by the sugar-phosphate backbone so are able to pair to free bases via complementary base pairing.

Question 28

How are bases joined together?

Answer 28

- Via hydrogen bonding

Question 29

What are 3 features of the non-specific immune system?

Answer 29

- The response is immediate. - The response is the same for all pathogens. - The response involves physical barriers and phagocytosis.

Question 30

What are 3 features of the specific immune system?

Answer 30

- The response is slower. - The response is specific to each pathogen. - The response involves lymphocytes.

Question 31

What must lymphocytes be able to do?

Answer 31

- Distinguish between self and non-self material.

Question 32

What are the proteins on the surface of cell membranes that are able to detect foreign material called?

Answer 32

- Antigens.

Question 33

What is a phagocyte?

Answer 33

- A type of white blood cell which carries out phagocytosis.

Question 34

What is phagocytosis?

Answer 34

- Mechanism by which cells engulf a pathogens to form a vesicle.

Question 35

Outline phagocytosis in 6 steps...

Answer 35

1) Phagocyte is attracted to a foreign chemical left behind 2) Phagocyte attaches to chemicals on the surface pf the pathogen via receptors. 3) Cytoplasm of the phagocytes moves around the pathogen and engulfs it causing a phagosome to be produced. 4) A lysosome fuses with a phagosome, releasing lyzozymes enzymes into phagosomes. 5) Lyzozymes hydrolyse the pathogen. 6) Phagocyte presents pathogen's antigens on its surface.

Question 36

What are 3 features of T lymphocytes?

Answer 36

- Made in the bone marrow. - Matured in the thymus gland. - Involved in the cell mediated response.

Question 37

What are 3 features of B lymphocytes?

Answer 37

- Made in the bone marrow. - Matured in the bone marrow. - Involved in the humoural response.

Question 38

Outline the cell-mediated response in 4 steps...

Answer 38

1) Phagocytosis occurs 2) Phagocyte presents antigens on its surface. 3) T helper cells bind to the antigen via specific T-cell receptors. 4) The binding activates T helper cells to divide rapidly by mitosis.

Question 39

What cells do T helper cells produce?

Answer 39

- Memory B cells - Stimulate phagocytes to engulf pathogens by phagocytosis - B cells - Cytotoxic T cells.

Question 40

What is the role of cytotoxic T cells?

Answer 40

- To kill abnormal cells and body cells infected by pathogens.

Question 41

How do cytotoxic T cells kill abnormal cells?

Answer 41

- By producing perforin, a type of protein. - Perforin makes holes in the membrane allowing full permeability causing cells to die.

Question 42

What is an antibody?

Answer 42

- A protein produced by B lymphocytes in response to the presence of the antigen.

Question 43

Outline the humoural response in 7 steps...

Answer 43

1) Surface antigens of an invading pathogen are taken in by endocytosis. 2) B cells process antigens and present them on cells. 3) T helper cells attach to receptors on the APC B cell to activate it. 4) B cells divides by mitosis (clonal selection) to produce plasma cells. 5) Plasma cells are produced which create antibodies specific to the antigen on the pathogen's surface. 6) Antibody-antigen complex is formed causing agglutination, making it easier for phagocytes to engulf pathogens. 7) B cells form memory cells which can rapidly divide into plasma cells.

Question 44

Why is the secondary response more efficient than the primary response?

Answer 44

- Secondary response allows antibodies to be produced at a faster rate. - Memory B cells can divide rapidly into plasma cells that produce specific antibodies to the antigen.

Question 45

What is a vaccine?

Answer 45

- The injection of an inactive pathogen which stimulates an immune response against a pathogen.

Question 46

Why are vaccines important?

Answer 46

- Vaccines stimulate memory cell production against a disease for the future.

Question 47

What is herd immunity?

Answer 47

- Herd immunity occurs when a large portion of a population becomes immune to a disease, either through vaccination or prior infection. - thereby reducing its spread and protecting those who are not immune.

Question 48

What is antigenic variability?

Answer 48

- Antigenic variability is the ability of pathogens to alter their surface proteins to evade detection by the host's immune system.

Question 49

What is active immunity?

Answer 49

- Active immunity is the protection against disease developed by an individual's immune system after exposure to a pathogen or through vaccination.

Question 50

What is passive immunity?

Answer 50

- Passive immunity is the temporary protection against disease gained by receiving antibodies from another source, such as maternal antibodies or antibody injections, without the immune system generating its own response.