SAC 1B

Question 1

Metabolism

Answer 1

 Total of all the chemical reactions occurring within a cell or organism
 Anabolism/Endergonic reactions:
o Energy is required- it ENTERS
o The building of more complex molecules from simple ones. Making New things
o E.g. photosynthesis
o A + B –> C
 Catabolism/Exergonic reactions
o Energy is released- it EXITS
o The breaking down of more complex molecules into simple ones. Cracking up things
o E.g. cellular respiration
o C –> A + B

Question 2

Heterotrophic

Answer 2

 Ingest or absorb organic matter

Question 3

Autotrophic

Answer 3

 Build organic compounds

Question 4

Enzymes

Answer 4

 Definition:
o Specific biological catalysts that speed up the rate of reactions by lowering activation energy. They are reusable, and so are required in small amounts.
o Without enzymes, metabolism would be so slow at body temperature that insufficient energy would be available to maintain life
o Catalyse reactions in both ways (reversible reactions)
 Structure:
o Completely made of protein
o Have an active site –> substrate combines to enzyme at this site, forming an enzyme-substrate complex

Question 5

Activation energy

Answer 5

 Energy required to initiate a reaction

Question 6

Cofactor

Answer 6

 Non-protein component needed by some enzymes to function

 Often inorganic (although organic ones are called coenzymes e.g. some vitamins)

Question 7

Substrate

Answer 7

 Compound acted on by an enzyme

Question 8

‘Lock-and-key’ theory vs. induced fit theory

Answer 8

 ‘Lock-and-key’
o Substrate fits into a pre-formed enzyme active site
 Induced fit
o Substrate binds to enzyme –> causes enzyme to change shape

Question 9

Factors affecting enzymes activity

Answer 9

 pH
o Optimal pH: generally 7.6 (pepsin- 2, trypsin- 8)
o Change from optimum can change the shape of the enzyme and affect its ability to combine with its substrate
 Temperature
o Optimal temp: 37C
o High temps: permanently denatured
o Low temps: inactivated, can become active again
 Enzyme concentration
o If the amount of enzyme is increased, the rate of reaction/production increases
o There will not be a change in the total amount of product made because enzymes are not used up during the reaction
 Substrate concentration
o If the amount of substrate increases, the rate of reaction initially increases until all of the active sites of the enzyme molecules become occupied
 Inhibition
o Other molecules competing with the normal substrate for the active of an enzyme

Question 10

ATP

Answer 10

	Usable energy
	Adenosine triphosphate
	Function:
o	Anabolic reactions
o	Cell growth
o	Tissue repair
o	Movement
o	Reproduction
o	Active transport
	Structure:
o	Made of 3 phosphate groups
o	Energy is released when 1 inorganic phosphate group breaks off from ATP --> this makes ADP + 1 inorganic phosphate group
o	ADP can become ATP again when an inorganic phosphate group is added

Question 11

Proteins

Answer 11

 Made of C,H,O,N,(S)
 Is a polymer, produces 1 molecule/bond of water during condensation polymerisation
 Amino acids are joined together in a peptide bond
 Amino acids (monomer):
o 20 different types  to make proteins/polypeptides
 Polypeptides:
o Enzymes: to speed up reactions. E.g. pepsin, amylase
o Hormones: e.g. insulin helps to lower blood glucose levels
o Antibodies
 Denaturing:
o Is when the tertiary structure of the protein is disrupted by heat or extremes of pH, and the function of the protein is altered as it cannot bind to its substrate

Question 12

Protein structure

Answer 12

 Primary structure: specific linear sequence of amino acids. @ ribosomes
 Secondary structure: folding of the amino acid chains. Can be folded into α-helix, β-pleated sheet, or random coiling. @ endoplasmic reticulum or cytoplasm
 Tertiary structure: further folding of the secondary structures due to interactions between ‘R’ groups. Many proteins are functional at this level. @ endoplasmic reticulum or cytoplasm
 Quaternary structure: when two or more polypeptide chains are bound to produce a functional structure. Not all proteins go to this stage, but the ones that need to are only functional at this stage. @ endoplasmic reticulum or cytoplasm

Question 13

Proteomics

Answer 13

 The study of the proteome, which refers to all the proteins produced in an organism in a particular environment

Question 14

Scientific method

Answer 14

• Hypothesis:
  o A cause (independent variable) + effect (dependent variable)
  o Use: “That/if ‘x’ is increased/decreased, then ‘y’ will happen/increase/decrease”
  o E.g. That light exposure will increase the rate of O2 bubbles produced (indicating increased rate of photosynthesis)
• Aim:
  o Use: “To investigate the effect of…” OR “To investigate whether…”
• Control + experimental group: one without IV, one with. Needed for comparison to measure effect of IV
• Sample size: 20-100 individuals in each group
• Controlled variables:
  o Use: at least 2 factors that must be kept the same that are specific and different to those used in the questions
  o E.g. same species, temperature, amount of water, same age, etc.
• State DV
• Expected results:
  o Can include diagrams
  o Use: “Hypothesis would be supported/rejected if…”
• Experiments should be REPEATED to increase amount of data + ­ validity of conclusions
• In questions do: IV, SS, CV, DV, Repeat experiment