C1.2

Question 1

Adenosine Triphosphate

Meaning of Phosphorylation?

Answer 1

• When a phosphate group is added to an ion/molecule, often to energise/activate it.
• Speficially, for this unit, the addition of THIRD phosphate group to Adenosine Diphosphate (ADP) forming a high energy bond that stores potential energy in the form of Adenosine Triphosphate (ATP).
• In short - the making/reacharging of ATP

Question 2

Adenosine Triphosphate

What is ATP hydrolysis?

Answer 2

• When a third phosphate group is broken off ATP (returning it to ADP)
• The addition of water breaks the bond and stabilises the phosphate group and ADP molecule
• An energy releasing reaction that provides energy for other cellular processes.

Question 3

Adenosine Triphosphate

What are three Cellular processes that require ATP?

Answer 3

• DNA Replication and protein synthesis
• The Power stroke that allows for sacromere contraction (muscle movement)
• Active transport of molecules against their conc. gradition –> NaK pumpt for action potential propagation.

Question 4

Adenosine Triphosphate

Why is ATP an ideal energy molecule?

Answer 4

• It contains three phosphate groups, ideal for stored energy. Groups are negatively charged & repel one another, creating an unstable convalent bond
• This unstable bond stores energy and has a low activation energy for breaking (easily broken by hydrolysis, releasing energy
• ATP is also water soluable, thus moves freely in the cytoplasm but does NOT cross the cell membrane.

Question 5

Adenosine Triphosphate

Compare endergonic and exergonic cycles of ATP and ADP.

Answer 5

• ATP hydrolysis is an exergonic reaction, third phosphate breaks, energy is released, that energy allows for endgeronic energy requiring processes like active transport to occur.
• ATP phosphorylation is endergonic, requiring energy, which comes from organic compounds/excitied electrons.

Question 6

Adenosine Triphosphate

How can ATP be regenerated?

2 sources of energy required

Answer 6

• Requires an energy source, as for ATP to be regenerated, ADP must be phosphorylated (endergonic reaction).

1. In CELLULAR RESP. the initial energy comes from food sources (preferably carbs, but also lipids and proteins). The majority of ATP made through transfer of electrons originating from food.
2. In PHOTOSYNTHESIS, ATP is regenerated to power the processs – initial energy comes from sunlight which excites electrons.

Question 7

Aerobic vs Anaerobic Respiration

What is Anaerobic Cellular Respiration?

Answer 7

• Processes that regenerate SMALL amounts of ATP WITHOUT OXYGEN
• First stage is glycolysis, creates 2 ATP without use of oxygen.
• Followed by fermantation, does NOT create further ATP but instead recycles products of glycolysis, allowing it to continue producing small amounts of ATP.

Question 8

Aerobic vs Anaerobic Respiration

What is Aerobic Cellular Respiration?

Answer 8

• Uses oxygen to produce up to 36 ATP
• Processes begins with glycolysis then moves into the mitochondira for the Krebs Cycle which prepares for the ETC (final stage through which LOTS of ATP is produced through activation of ATP synthase.
• ETC requires oxygen

Question 9

Aerobic vs Anaerobic Respiration

What is fermentation?

Answer 9

• The second stage of anaerobic cell resp. following glycolysis
• Does not create energy, just recycles NADH into NAD+/co-enzyme allowing for glycolysis to restart
• Two types

Question 10

Aerobic vs Anaerobic Respiration

What are Respirometers?

Answer 10

• Device measuring oragnisms rate of respiration via measuring rate of oxygen consumption
• Sealed units, including a chemical that absorbs all CO2 to changes in gas volume reflect oxygen intake
• Often a coloured fluid that moves through tubing as O2 is pulled into the respirometer.

Question 11

Aerobic vs Anaerobic Respiration

What are the events of Glycolysis?

PLOA

Answer 11

• Phosphorylation of glucose, uses 2 ATP.
• Lysis of 6 carbon sugar into two TRIOSE phosphate.
• Oxidation of sugar/carbohydrate, hydrogen molecules are removed from the carbohydrate to REDUCE NAD (2 NADH made)
• ATP Creation Dephosphorylation of the carbohydrates, making ATP and creating PYRUVATE.

Question 12

Aerobic vs Anaerobic Respiration

What are the 5 differences between aerboic and anaerobic respiration?

Answer 12

• Anaerboic: reactant is glucose alone, occurs in the cytoplasm, yields 2 ATP (low), goes through glyolysis then fermentaiton, produces lactic acid (animal cells) or ethanl + CO2 (plant cells)
• Aerboic: reactant is glucose AND oxygen, occurs in the mitochondria, yields 36-38 ATP (high), goes through glycolysis, link reaction, krebs cycle, ETC, produces CO2 and H2O.

Question 13

Aerobic vs Anaerobic Respiration

What is the difference between alcoholic and lactic acid fermentation?

Both convert pyruvate sugar into another waste product to regenerate NAD

Answer 13

• Lactic Acid: produces lactic acid (done by muscles during rigorous exercise), reversible in presence of O2.
• Alcoholic: produces ethanol and CO2 (done by yeast and plants)

Question 14

Aerobic vs Anaerobic Respiration

What are factors that affect the rate of cellular respiration?

Answer 14

• Temperature (impacts enzymes)
• Conc. of O2 & CO2
• Glucose and other carbon source availability
• Type and purpose of cell

Question 15

Glycolysis and Kreb’s Cycle

What is a Co-enzyme?

Answer 15

• Non-protein small molecule, supports functioning of an enzyme/reaction it catalyses.
• Focusing on Hydrogen/electron carrier used by the enzymes of cell resp. to move H-protons and electrons to the ETC.
• These are NAD, FAD, NADP

Question 16

Glycolysis and Kreb’s Cycle

What is lysis in the context of glycolysis?

Answer 16

• Breaking down of glucose into two 3-carbon sugars
• Formation of an unstable six carbon sugar requires ATP
• Unstable sugar easily lyse into two triose phosphate molecules (three-carbon sugars with phosphate attached)

Question 17

Glycolysis and Kreb’s Cycle

What is the role of NAD in Cellular Respiration?

Answer 17

• NAD (and FAD) collect the hydrogen atoms when they are removed from the carbohydrate and transfer them to the mitochondiral inner membrane
• Required for ATP synthase to be activated, as a proton gradient must be established.

Question 18

Glycolysis and Kreb’s Cycle

Why is fermentation necessary for glycolysis to continue?

Answer 18

• Glycolysis produces 2ATP, 2 pryuvate and 2 NADH.
• ATP can be used but a cell has limited NAD/NAD+, so if NADH not oxidized, glycolysis will stop and cell can’t make any more ATP.
• Fermenation has the purpose of oxidizing NADH back to NAD by transferring hydrogen to pyruvate to make a different waste product - either lactic acid or ethanol.

Question 19

Glycolysis and Kreb’s Cycle

What is the purpose of the link reaction?

And what happens in it?

Answer 19

• After glycolysis, pryuvate diffuses into mitochondria.
• Pyruvate is converted into Acetylo CoA in the link reaction (required for Kreb’s to begin)
• Involves the decarboxylation of pyruvate (releasing CO2) and then oxidation of pyruvate (reducing NAD to NADH)
• Coenzyme A is added to create the Acetyl CoA which will start/enter the Kreb’s cycle.

Question 20

Glycolysis and Kreb’s Cycle

What is the role of Citrate in the Krebs Cycle?

Answer 20

• Each Acetyl CoA is a 2 carbon sugar, when entering Krebs, it combines with oxaloacetate/4-carbon recyclable sugar
• CoA detaches, the6-carbon molecule is citrate which is the official Start of the oxidation and decarboxylation steps of Krebs.

Question 21

Glycolysis and Kreb’s Cycle

What are the products of Link Reaction and Krebs?

Note that Link and Krebs are often considered one step of aerboic resp.

Answer 21

• per GLUCOSE (one cycle is for one pryuvate, so final products are twice as much)
• LINK: 2 Carbon dioxide, 2 NADH, 2 Acetyl CoA
• KREBS: 4 Carbon dioxide, 6 NADH, 2 FADH, 2 ATP

Question 22

Oxidative Phosphorylation

What is an Electron Transport Chain?

Answer 22

• A series of proximal membrane proteins that’s primary purpose is to build a proton gradient.
• It faciliates the transfer electrons between protein pumps and lipid soluable carriers that move electrons.
• Proton pumps, which when energised by electrons moving from the oxidation of 10xNADH, can move a hydrogen proton across the membrane (from matrix into the intermembrane space)
• Drives the final stage of aerobic resp.

Question 23

Oxidative Phosphorylation

What is a proton gradient?

And why is it important?

Answer 23

• The accumulation of hydrogen protons – the goal of ETC.
• Important because ATP synthase PASSIVELY diffuses hydrogen protons down its channel, with a proton revolving drum that when H+ move through, releases kinetic energy which drives the phosphorlyation of ADP into ATP.

Question 24

Oxidative Phosphorylation

What is Chemiosis?

Separate from the ETC, but requires it.

Answer 24

• Osmosis but a chemical ion channel rather than for water.
• It is the movement of hydrogen protons through the protein channel ATP synthase, creating ATP in the process.

Question 25

# Oxidative Phosphorylation What is metabolic water? | Final product

Answer 25

* After Hydrogen protons **and electrons** have been used to build the proton gradient and create ATP, hydrogen must be removed. * Done through **combining hydrogen with electrons and oxgyen** (terminal electron acceptor) to create water as the final, safe waste product (metabolic water).

Question 26

# Oxidative Phosphorylation Why is NADH and FADH essential for the ETC?

Answer 26

* **ATP synthase** requires a **proton gradient** in the intermembrane space to be activated, which requiers the movement of H+ **into the intermembrane space**, which requires **activation of pumps** by **excited electrons** moving through the ETC. * The **SOURCE** of both **protons and electrons** is NADH and FADH. * They move to the edge of the matrix and are then **oxidezed**, removing the hydrogen, which **splits** into a **proton and an energised electron**.

Question 27

# Oxidative Phosphorylation What is the role of ATP synthase?

Answer 27

* Capable of **phosphorylating ADP**, but this requires an energy source. * The protons moving with their concentration gradient move through a **drum like rotating upper section** within the membrane that produces **KINETIC ENERGY** that allows the *enzymatic lower subunits* to catalyse the addition of a free phosphate to **ADP to make ATP**

Question 28

# Oxidative Phosphorylation What is the role of oxygen in aerobic cellular respiration? | Think about metabolic water

Answer 28

* The **terminal electron acceptor** in aerobic respiration. * When electrons finish the ETC, and protons have moved through ATP synthase, they require an **electron accepter** with a**HIGH affinity** for electrons, creating safe metabolic waste. * Oxygen has a high affinitiy, pulls electrons from last carrier, returns protons from matrix to make a wate.r

Question 29

# Oxidative Phosphorylation How do triglcerides differ from glucose as a respiratory substrate? | Triglcerides are lipids, Sugars (e.g., glucose) are carbohydrates

Answer 29

* **Lipids** must be broken into glycerol and fatty acids which go **DIRECTLY** into Krebs Cycle (glysolysis does **not occur**) and generate more energy per gram due to their high desnsity of carbon and hydrogen. * Fatty acids are **converted to Acetate (lots of 2c)** straight in Krebs cycle, no glycolysis needed.