Biological Fuel - Carbohydrates

Question 1

What is cellular respiration?

Answer 1

Most efficient way to obtain energy from carbohydrates
The breaking them down of carbs to generate energy

Carbs + Oxygen > CO2 + H2O + Energy

Question 2

What is ATP?

Answer 2

Energy is produced in cells in the form of a molecular called Adenosine Triphosphate (ATP)

It is the currency and store of energy in cells and drives a variety of chemical reactions eg membrane pumps and the reproduction and movement of cells

Question 3

What is ATP formed from?

Answer 3

ATP is formed from ADP in an energy consuming reaction
Energy is released from ATP when it is hydrolysed back to ADP
(Remember how G-protein receptors work)

Question 4

What are the three types of carbohydrates / sugars?

Answer 4

1. Monosaccharides
2. Disaccharides
3. Polysaccharides

Question 5

What are monosaccharides?

Answer 5

Simplest carbohydrate containing a single sugar

Examples = ribose, fructose, and glucose

Question 6

All sugars are made of the same chemical components but different spatial arrangements to create diversity. Because of this, suagrs can be described as isomers and / or optical isomers, what does this mean?

Answer 6

Isomer = same chemical formula but different orientations to form different sugars

Optical isomer = mirror image of a single sugar

Question 7

What is the function of monosaccharides?

Answer 7

Priamrily used immediately as fuel, if this is not possible then they are stored as a di or polysaccharide

Question 8

What are disaccharides?

Answer 8

Transport sugars made up of 2x monosaccharides joined with a glycosidic bond

Different types determined by which monosaccharides are joined:
Sucrose = Glucose + Fructose
Lactose = Galactose + Glucose
Maltose = Glucose + Glucose

Question 9

What are polysaccharides?

Answer 9

Used for the storage of sugars and are polymers of 100s to 1000s of monosaccharides

Example = Glycogen, which is the major store of glucose in humans, tends to be short term storage that is depleted in a day

Question 10

Metabolism is a process made up of two opposing chemical reactions, what are they and what do they do?

Answer 10

Catabolism = breakdown of foodstuffs into smaller molecules to generate energy

Anabolism = uses the energy from catabolims to drive the synthesis of other molecules

Question 11

What is aerobic respiration?

Answer 11

The most efficient catabolic reaction used to generate energy (ATP), most commonly using glucose

Question 12

The fundamental underlying processes of aerboic reactions are reduction and oxidation, also known as redox reactions. What are they?

Answer 12

Redox reactions decompose glucose to yield energy through the transfer of electrons (-ve charge)

Reduction = gain of electrons
Oxidation = loss of electrons

Example:
Na and Cl
Na is oxidised, Cl is reduced
Result = Na+ and Cl-

Question 13

How specifically does the respiration of glucose work via redox reactions?

Answer 13

1. Glucose has an abundance hydrogens and therefore electrons
2. The hydrogen from glucose will be transferred to oxygen via redox reactions
3. Complete oxidation of glucose forms O2
4. Complete reduction of oxygen forms H2O

C6 H12 O6 + 6(O2) > 6(CO2) + 6(H2O)

Question 14

How do redox reactions work to extract energy?

Answer 14

Series of steps relying on active carriers as intermediaries
Carriers accept electrons and store temporarily
NAD+ is oxidised state, NADH is reduced state
The transfer of electrons from, NADH to oxygen leads to ATP generation

Question 15

What are the stages of aerobic respiration?

Answer 15

1. Glycolysis
2. Citric Acid Cycle / Krebs Cycle
3. Oxidative phosphorylation

Question 16

What is glycolysis and how does it work?

Answer 16

The breakdown of glucose into pyruvate in cytosol

Glucose (6 carbons) is split into 2 pyruvate molecules (3 carbons)
There is an absence of oxygen and electrons are removed from glucose and transfered as part of redox reactions to form NADH

Glucose + 2x ATP = 2x NADH, 4x ATP, 2x Pyruvate

Question 17

What is the citric acid cycle / krebs cycle?

Answer 17

The complete oxidisation of pyruvate within the mitochondria to produce lots of electron carriers

This requires oxygen and is broken down into 2 stages: oxidation of pyruvate and the krebs cycle

Question 18

How does the citric acid cycle function?

Answer 18

1. Pyruvate (3 carbons) becomes Acetyl CoA (2 carbons)
2. Aceytl CoA is completely oxidised to form CO2

This process accoutns for 2/3 oxidation of carbon compounds in cells and produces LOTS of electron carriers (NADH and FADH2), generating ATP

Question 19

What is oxidative phosphorylation?

Answer 19

The transport of electron chains within the mitochondria which establishes a H+ gradient

ATP is synthasised from this gradient generating the MOST ATP in aerobic respiration

Question 20

What are the different fuels and their entry points for aerobic respiration?

Answer 20

1. Carbohydrates (digetsed prior to entry and start at glycolysis)
2. Proteins (Need to be broken down into amino acids before entering directly into citric acid cycle)
3. Fats (Need to be broken down to glycerol or fatty acids before entering during glycolysis and citric acid cycle respectively)