Cellular respiration, metabolism and enzymes

Question 1

Metabolism:

Answer 1

→ sum of all chemical reactions within a cell

Question 2

Catabolism:

Answer 2

→ releases energy to breakdown complex molecules

Question 3

Anabolism:

Answer 3

→ consumes energy to synthesis of complex molecules

Question 4

Change in free energy (ΔG):

Answer 4

→ difference between free energy of final and initial states

Question 5

Differences between anabolic reactions and catabolic reactions:

Answer 5

Question 6

Adenosine triphosphate=

Answer 6

Adenine nitrogenous base + ribose sugars + 3 phosphate groups

Question 7

Hydrolysis of ATP:

Answer 7

Question 8

How does ATP function in powering cellular work? (3)

Answer 8

➔ By coupling exergonic with endergonic reactions

Chemical work: Hydrolysis of ATP into ADP is an exergonic reaction as it releases energy. This energy is then used to push endergonic reactions to make complex molecules.

Transport work: Hydrolysis of ATP releases energy which helps pump potassium out of cells and sodium into our cells. Active transport of cells across a membrane.

Mechanical work: Hydrolysis of ATP can allow for energy to be used to contract muscles and do work.

Question 9

ATP is a renewable resource that can be regenerated by __ ____ to ADP.

Answer 9

+ phosphate

Question 10

What are enzymes?

Answer 10

→ biological catalyst that speeds up a reaction without being consumed by the reaction.

Question 11

What are the characteristics of enzymes? (4)

Answer 11

• Enzymes are reaction-specific
• Lock and key complex
• Since enzymes are proteins, can change shape.
• When an enzyme changes shape to better grasp substrate → induced fit

Question 12

What is activation energy?

Answer 12

The minimum energy required to start reaction/energy required to contort/bend the reactant molecule so that
bonds can break.

Question 13

How do Enzymes lower Activation energy?

Answer 13

1. Enzyme has an active site to which substrate binds → Enzyme-substrate complex
2. Active site reshapes to better grasp substrate known as
   → induced fit. Substrates are held together via weak interactions = hydrogen or ionic bonds
3. Active site can lower Activation energy and speed up
   reaction
   - Acting as a template for substrate orientation, bringing
   substrates together in a way that the new bond is going
   to form.
   - Stresses the substrate and stabilises the transition state
   to speed up the production of products.
   - Provides a favourable microenvironment
   - Participates directly in the catabolic reaction
   BUT: enzyme must return to its original shape in order to
   catalyse reaction again,
4. Substrates are converted to products
5. Products are released leaving the active site exposed to more substrates to bind to, further increasing speed of reaction.

Question 14

Optimal conditions: (2)

Answer 14

1. Optimal temperature
2. Optimal pH

Question 15

Cofactor →

Answer 15

→ non-protein helper required to activate enzyme

Question 16

1. Inorganic (___, ___, ___,___)
2. Organic = ____ (_____).

Answer 16

1. Inorganic (Z, Fe, Cu ions)
2. Organic = coenzyme (vitamins)

Question 17

What is an enzyme inhibitor?

Answer 17

→ selectively inhibits the action of specific enzyme

Question 18

What are the effects of an enzyme inhibitor? (2)

Answer 18

1. Permanent
2. Reversible

Question 19

What is competitive inhibition? (2)

Answer 19

→ competitive inhibitor binds to the active site and takes place of the substrate so that substrate-enzyme binding cannot take place
→ competes with the substrate for the active site

Question 20

What is non-competitive inhibition?

Answer 20

→ non-competitive inhibitor binds away from the active site, but in binding, causes the active site to change shape, not allowing for substrate-enzyme binding

Question 21

What is allosteric regulation? (4)

Answer 21

• Type of non-competitive inhibition – binding away
  from the active site.

‘Allo’ = different ‘Steric’ = form

• Protein function at one site is affected by the binding of a regulatory molecule to a separate site.
• An allosteric enzyme has 4 subunits, each with its own active site.
• A regulatory/allosteric site is also present between the active site subunits.

Question 22

How does an allosteric enzyme oscillate?

Answer 22

The allosteric enzyme oscillates between active (can bind with substrate) and inactive (changed shape therefore cannot bind with substrate) forms.

Question 23

What is the function of the inhibitor and activator?

Answer 23

1. Activator can bind to the regulatory site and stabilize the allosteric enzyme at the active form.
2. Inhibitor can bind to regulatory site and stabilize the allosteric enzyme at the inactive form.

Question 24

The shape change in one subunit will be_____ to all the other subunits.

Question 25

Cooperativity: (5)

Answer 25

➔ substrate binds to one active site which stabilizes conformational changes in other subunits ➔ Binding of one substrate molecule to one active site locks all subunits in active form to quickly catalyse reaction ➔ E.g., haemoglobin (not an enzyme) – when one Oxygen binds to one active site, haemoglobin becomes more likely to bind 3 more Oxygens ➔ This mechanism amplifies the response of enzymes to substrates: One substrate molecule primes an enzyme to act on additional substrate molecules more readily. ➔ Considered allosteric regulation because even though substrate is binding to an active site, its binding affects catalysis in another active site.

Question 26

Feedback Inhibition: (2)

Answer 26

- Final product binds to and inactivates the enzyme to prevent excess of product accumulating. - The product of one enzyme-substrate reaction becomes substrate for next enzyme in metabolic pathway.

Question 27

What is cellular respiration?

Answer 27

→ cells breaking down glucose to form ATP energy

Question 28

What is energy harvesting?

Answer 28

→ collecting ATP energy through process of cellular respiration

Question 29

What redox reaction takes place during cellular respiration?

Answer 29

Recap: OILRIG – Oxidation is loss of e-, Reduction is gain of e- Sugar (reducing agent ∴ undergoes oxidation) + Oxygen (oxidising agent ∴ undergoes reduction) → Carbon dioxide + Water + ATP energy + heat energy (released as by-product) C6H12O6+ 6O2= 6CO2+ 6H2O + energy

Question 30

What is an electron carrier?

Answer 30

Electron carrier → a coenzyme named NAD+ (nicotinamide adenine dinucleotide) functions as an oxidising agent during respiration ∴ picks up e-, becomes reduced

Question 31

Level of energy throughout the process: Coupling of endergonic and exergonic reactions

Answer 31

1. Exergonic reaction is catabolic which breaks down complex molecules into simpler molecules, releasing energy, going from a high energy state to a low energy state 2. In the diagram, energy is released in form of e- 3. Electron will be picked up via endergonic reaction by NAD+, which becomes reduced (gains 2e-) 4. NAD+ picks up 2e- and Hydrogen to become neutral → depleted carrier 5. This depleted carrier is reduced, an increase in energy, becoming NADH → energized carrier → stored energy 6. NADH drops off e- and is oxidised leading to another set of an endergonic reaction 7. Net exergonic ‘downhill’ reaction - Energy is lost as heat when energy is transferred - Reaction not efficient

Question 32

What is the difference the between uncontrolled reaction and cellular respiration? (2)

Answer 32

a) Uncontrolled reaction → if the electrons harvested are directly transferred to water, there will be an explosive release of energy as heat and light ∴ not enough energy for cellular work b) Cellular respiration → controlled release of energy because electron carrier transports electrons to an electron transport chain which allows for the slow release of ATP energy at each step and eventually, the electrons combine with Oxygen (final e- acceptor) to form water

Question 33

What steps are involved in cellular respiration? (5)

Answer 33

Question 34

What takes place during Glycolysis? (6)

Answer 34

1. Takes place in the cytosol 2. Energy is added to the glucose molecule 3. Molecule splits into half 4. NAD+ picks up e- and H, → electron carrier 5. For every 1 glucose molecule, 2 ATP are produced → substrate-level ATP produced 6. End product is pyruvate

Question 35

What takes place during Acetyl CoA Formation? (4)

Answer 35

1. Pyruvate enters mitochondria 2. One carbon dioxide falls off forming CO2 3. Electrons are stripped forming NADH 4. Coenzyme A attaches to 2-carbon fragment forming Acetyl CoA

Question 36

What takes place during the Citric Acid Cycle / Krebs Cycle? (5)

Answer 36

1. Coenzyme A is removed and remaining 2-carbon fragment attaches to an existing 4-carbon molecule 2. Starting point for Citric Acid cycle 3. 6-carbon chain is broken down releasing CO2 4. Electrons are captured by e- carriers and more CO2 is produced 5. 2 ATP is produced for each glucose molecule → substrate-level ATP produced

Question 37

What takes place during Oxidative Phosphorylation: Electron Transport + Chemiosmosis? (7)

Answer 37

1. NADH deliver electrons to electron transport chain embedded in inner membrane of mitochondria 2. Chain consists of electron carriers (proteins) 3. Electrons are transferred from one e- carrier to the next, slowly releasing energy 4. Oxygen you breathe pulls e- from transport chain and forms water as by-products 5. Energy released from e- is used to pump H ions across the inner membrane of mitochondria creating high concentration of H ions 6. These H ions flow back across membrane through a turbine 7. Flow of hydrogen ions spins turbine which activates ATP production → oxidative/ more ATP

Question 38

Cellular respiration is regulated via feedback ____.

Answer 38

inhibition

Question 39

How does the Regulation of Cellular Respiration take place? (3)

Answer 39

The end products ATP and citrate (from citric acid cycle) inhibit early enzyme (Phosphofructokinase) in glycolysis to prevent production or accumulation or waste of products that are not required. AMP – adenosine monophosphate (low energy form) When there is a high accumulation of AMP or ADP, it will stimulate cellular respiration so that more energy can be produced. Stimulates Phosphofructokinase to break glucose molecule.

Question 40

Versatility of Cellular respiration:

Answer 40

Question 41

What is biosynthesis? (2)

Answer 41

- Anabolic pathway required to synthesise more complex molecules - Glycolysis and citric acid cycle function as metabolic interchanges → the intermediates produced as a result of the reactions can further form other complex molecules via an anabolic pathway

Question 42

What are essential nutrients?

Answer 42

Essential nutrients are molecules that animals cannot make through biosynthesis → they must be consumed as pre-assembled organic molecules and minerals.

Question 43

What do the essential nutrients include? (4)

Answer 43

- Essential amino acids - Essential fatty acids - Vitamins - Minerals

Question 44

What are essential amino acids?

Answer 44

Essential amino acids - about half (10 of 20) amino acids required by for protein synthesis within our cells cannot be produced and these essential amino acids must be consumed through

Question 45

What are essential fatty acids?

Answer 45

Essential fatty acids - our bodies lack the enzyme required to form double bonds in fatty acids and we therefore need to consume two essential fatty acids (omega-3 and omega-6) in seeds, grains and vegetables.

Question 46

What are vitamins? (2)

Answer 46

- Vitamins - our bodies require 13 essential vitamins, 9 of which are water-soluble (vitamin C and 8 vitamin B complex) and 4 of which are fat-soluble (vitamin A, D, E, K). - Can be lipid-soluble (transported by proteins, can be stored) or water-soluble (easy transport, needs to be regularly taken in)

Question 47

What are minerals?

Answer 47

Minerals - our bodies require 16 essential minerals, which are divided into major minerals (macrominerals) and trace minerals (microminerals) depending on the amount required by the body.

Question 48

Bioavailability – degree of ____ absorption High bioavailability → > __% of minerals can be absorbed Low bioavailability → < __% of minerals can be absorbed

Answer 48

mineral 40% 10%

Question 49

What is malnutrition?

Answer 49

Malnutrition is an imbalance between nutritional intake and nutritional needs and can result from either nutritional deficiencies (undernutrition) or an excess of certain nutrients (overnutrition). Hidden hunger → when you think you are eating enough but you are not