Cellular Respiration

Metabolism

All the chemical reactions that take place in cells

Metabolic processes

Catabolism: breaks larger molecules into smaller ones → releases energy

Anabolism: builds smaller molecules into larger ones → requires energy

Cellular respiration

process by which organic molecules are broken down in cells to release energy for cell’s activity

Cellular respiration equation

C6H12O6 + 6O2 → 6CO2 + 6H2O + Energy

glucose + oxygen → carbon dioxide + water + energy

summarises 20+ smaller reactions that intermediately release energy → controls energy release

What happens with the energy released in body

60% is lost as heat → maintain body temperature

40% is used as ATP

Catalyst

a substance that increases the rate of reaction without being consumed in the process.

How is energy released from ATP?

Anabolism of the phosphate molecule with ADP requires energy, so the energy is stored between the bond of the second and third phosphate molecule of ATP

When the bonds are broken in catabolism, energy is released.

What does our cell use energy for?

• build complex molecules → anabolism

• movement of cell

• active transport

• cell division & growth

Glycolysis

glucose is broken down in a series of 10 steps

produces 2 pyruvate molecules and 2 ATP molecules

Aerobic Respiration

respiration requiring oxygen

1. Glycolysis

   enter mitochondria

2. Conversion to Acetyl CoA

3. Krebs Cycle (a.k.a. Krebs Cycle) → in matrix

4. Electron Transport System → in cristae

releases maximum 38 molecules of ATP

Conversion to Acetyl CoA

2 pyruvate molecules enter mitochondria convert to Acetyl CoA by losing two carbon molecules (oxygen needs to be present in order to bind to the carbon molecules)

produces 2 carbon dioxide molecules

Krebs Cycle

Each molecule goes through the Krebs cycle seperately

This produces a total of 4 carbon dioxide molecules and 2 ATP molecules (or 2CO2 and 1ATP each)

Electron Transport Cycle

Electrons are passed through an electron transport chain, releasing ATP each time

approx 26-34 ATP produced & water

Anaerobic Respiration

respiration without the presence oxygen

1. Glycolysis

2. 2 pyruvate molecules → lactic acid

all occurs in cytoplasm

very important during vigorous activity where oxygen is at a shortage

Accumulation of lactic acid

causes pain and fatigue → taken to liver by blood where it combines with oxygen to form glucose and glycogen

but in order for this to happen, oxygen debt must be repaid

Inorganic compounds

are not based from the carbon chain

usually doesn’t contain carbon but those that do (e.g. carbon dioxide) are small molecules

• water → dissolves other substances in chemical reaction

• vitamins → coenzymes for chemical reactions

• minerals → may be part of enzymes, cofactors for enzymes or part of ATP

Organic compounds

contains a carbon chain

• carbohydrates

• proteins

• lipids

• RNA → help in protein production

• DNA

Nutrients

any substance that provides energy, is essential for growth or assists in the functioning of the body

• water

• minerals

• vitamins

• carbohydrates

• proteins

• lipids

Carbohydrates

main energy source for the cell

• monosaccharide → glucose, fructose & galactose

• disaccharide → sucrose, maltose & lactose

• polysaccharides → glycogen, cellulose, starch

Lipids

broken down to fatty acids & glycerol → for cellular respiration

lipid molecules → made of one glycerol molecule and 1-3 fatty acid molecules

• most common is triglyceride → 3 fatty acid molecules and one glycerol molecule

Proteins

are enzymes → crucial to metabolism

there are 20 different types of amino acids - each differ in the structure

1. Dipeptide → two amino acids bonded by a peptide bond

2. Polypeptide → more than 10 amino acids

3. Protein → 100 or more amino acids

Enzyme

proteins that function as organic catalysts without being used up in the process

• specific biological catalysists

• we would die without them as reactions would be too slow

What do enzymes do?

• lowers activation energy needed to undergo chemical reactions

• can have catabolic and anabolic functions

• specific

Active site

The site where an enzyme binds to it’s substrate

is complementary to the shape of the substrate

Lock & Key Model

Shape of enzyme (the key) is complementary to the shape of the substrate (the lock), just how only the complementary key can fit into it’s lock

Induced Fit Model

When the enzyme and substrate join, the active site will slightly change to fit exactly

Rates of catalysis can be increased by:

• increasing molecular motion of particles → increased kinetic energy via higher temp

• increasing concentration of particles

  both leads to more collisions

Denaturing of proteins

enzymes denature when they are outside their optimum pH or temp

this alters charge of enzyme that overall changes it’s shape

can no longer bind to it’s specific substrate

Factors affecting enzyme activity

• enzyme concentration increases activity

• substrate concentration increases → until saturation

• temperature increases

• optimum pH → depends on enzyme

• cofactors and coenzymes → change the shape of active sites so the enzyme can combine with the substrate

• enzyme inhibitors → decreases activity

• product of the reactant must be continually removed

Cofactors

typically metal ions or non-protein molecules (iron)

Coenzymes

non-protein organic molecules (vitamins)

Enzyme inhibitors

• substances that slow or stop an enzyme’s activity (penicillin)

  • to control reaction’s products to specific amount

Optimum pH in different parts of the body

• stomach = 2 (pepsin)

• mouth = 7 (amylase)

• intestine = 7-9

Optimum temperature

around 37ºC

At what temperature does an enzyme start to denature?

past 37ºC

How do low temperatures affect enzyme activity?

• insufficient thermal energy → reduces kinetic energy

• less collisions

Saturation

Occurs when there are more substrates than enzymes, so all enzymes are bound and reacting

Rate of activity will cease to increase and plateau’s

Removal of products

must be continually removed

otherwise rate of reaction will slow because it becomes more difficult for collisions to occur