metabolism

Question 1

metabolism

Answer 1

metabolism is the sum of all reactions, the chemical processes that take place on the body

these chemical processes convert the food you eat into energy and materials needed for all life processes

all steps in metabolic reactions require the presence of an enzyme

Question 2

anabolic reactions

Answer 2

• build up
• anabolic reactions construct simple substances into complex substances
• use energy e.g. photosynthesis & protein synthesis

Question 3

catabolic reactions

Answer 3

• are destructive metabolic processes
• complex substances are broken down into simpler ones
• release energy e.g. cellular respiration & digestion

Question 4

what are enzymes?

Answer 4

enzymes are proteins that catalyse specific chemical reactions without themselves being altered (speeds up reactions) enzymes are organic catalysts

Question 5

features of enzymes

Answer 5

1. all enzymes are proteins
2. all enzymes speed up chemical reactions
3. all enzymes are not used up in the reaction
4. all enzymes are reaction specific
5. each enzyme works under specific conditions e.g. pH & temperature
6. enzymes are thought to work on lock-key principle
7. enzymes often work in systems with co-enzymes & co-factors

Question 6

activation energy

Answer 6

• activation energy is the energy needed to start a chemical reaction
• enzymes function by lowering activation energy
• this works to speed up the rate of chemical reactions

Question 7

lock key model

Answer 7

• the lock key model is an analogy put forward to explain the specific action of an enzyme with a single substrate
• enzyme + substrate entering active site → enzyme + products leaving active site
• temperatures above 40 degrees Celsius cause enzyme to denature, change in shape making it unable to bind with substrates
• the shape of enzyme (key) is always complementary to the shape of the substrate (lock)
• active site is complementary to the shape of the substrate

Question 8

induced fit model

Answer 8

when an enzyme and substrate join, they form weak bonds that cause the shape of the enzyme to change, creating complementary shapes

Question 9

factors affecting enzymes activity

Answer 9

• as enzyme concentration increases, the rate of the reaction increases
• as substrate concentration increases, the rate of the reaction increases, but only until a certain concentration or it will cease to have an effect as all the active sites of the enzyme will be fully occupied
• enzymes have an optimal temperature (30°C - 40°C) for maximum impact on the rate of reaction, beyond 40 degrees celsius, enzyme’s structure changes hence becoming denatured and shape of the enzyme is crucial for its functioning, once the enzyme molecule is denatured, the enzyme reduces or stop its function
• products of the reaction must be continually removed otherwise the reaction rate will be slow
• enzymes are sensitive to the pH of the medium in which a reaction takes place, has an optimum pH which it works most effectively at
• enzymes require presence of certain ions or non-protein molecules before they will catalyse a reaction called co factors, cofactors change the shape of the active site so that the enzyme can combine with the substrate, without it the enzyme molecule is intact, some cofactors are non-protein organic molecules called co enzymes
• enzyme inhibitors are substances that slow or even stop the enzyme’s activity, may be used by cells to control reactions so that products are produced in specific amounts e.g. some drugs

Question 10

what is ATP and how is it formed?

Answer 10

molecules of ATP store much of the released energy

Adenosine Diphosphate → Adenosine Triphosphate

ATP forms when chemical reactions release sufficient energy to bond a third phosphate group to ADP

Question 11

aerobic respiration

Answer 11

• in presence of oxygen
• food molecules breaking down
• glucose + oxygen → carbon dioxide + water + energy
• most of the energy is needed for the movement of cellular organelles and cell maintenance

Question 12

what are the phases of aerobic respiration + description

Answer 12

1. Glycolysis: takes place in cell cytoplasm, 2ATP being produced when glucose breaks down to 2 pyruvic acids
2. Link Reaction: takes place within the fluid of the matrix of the mitochondrion, CO2 being produced when 2 pyruvic acid →2 acetyl CoA
3. Kreb’s Cycle: takes place in the cristae of the mitochondrion, forms CO2, 2 ATP and 2H
4. The Electron Transport Chain (ETC): takes place in the cristae of the mitochondrion, 2H go through the electron transport chain forming up to 34 ATP

Question 13

what is the end result of aerobic respiration

Answer 13

CO2 + H20 + up to 38 ATP

Question 14

anaerobic respiration

Answer 14

• breakdown of food molecules to generate energy
• in the absence of oxygen
• within muscle cells

Question 15

what are the phases of anaerobic respiration + description

Answer 15

1. GLYCOLYSIS: takes place in cell cytoplasm, 2ATP being produced when glucose breaks down to 2 pyruvic acids
2. 2 pyruvic acid forms 2 lactic acid molecules

Question 16

what is the end result of anaerobic respiration

Answer 16

2 ATP and 2 lactic acid molecules

Question 17

SA:V ratio

Answer 17

surface area : volume
cells are small because they need to move wastes and gain nutrients quickly, being small cause them to have a larger surface area than volume, dependency on diffusion for getting substances into and out of the cell

When cells grow, their volume (the cytoplasm and contents) increases at a much faster rate than their surface area (the cell membrane). This is because volume (V) increases by a cube factor which surface area (SA) increases as a square factor.

As a cell grows, the ratio between surface area and volume (SA:V) decreases.

Thus as a cell grows, there is comparatively less membrane for substances to diffuse through and comparatively more cytoplasm/organelles that need these substances.