Cellular Respiration

Year 12 Biology U3 AOS 2

Cellular Respiration

the process by which all living things — plants, animals, fungi, protists, bacteria — create energy in the form of ATP

• Involves breaking down of glucose → CO2 and H2O, releasing energy

• The complete breakdown of glucose requires oxygen (aerobic)

• ATP is a coenzyme

Chemical Equation for Cellular Respiration

C6H12O6 + 6O2 → 6CO2 + 6H2O + ATP (energy)

Worded Equation for Cellular Repiration

glucose + oxygen → carbon dioxide + water + energy

Mitochondrial Structure — Why is it well suited to its function?

the inner membrane (cristae) is highly folded

• Providing a large surface area for important chemical reactions (e.g: ETC)

Glycolysis

sugar-breaking/splitting, occurring in the cytoplasm

INPUTS of Glycolysis

• Glucose

• NAD+

• ADP + P

OUTPUTS of Glycolysis

• Pyruvate (used in Krebs Cycle)

• NADH (used in ETC)

• 2 NET ATP (used for cellular processes) → makes 4 ATP though

Link Reaction (Modified Pyruvate)

a chemical reaction where pyruvate is transported into the mitochondria, attaching to an enzyme + becomes Acetyl CoA

Krebs Cycle (Citric Acid Cycle)

a central series of biochemical reactions, occurring in the mitochondrial matrix

INPUTS of the Krebs Cycle

• Pyruvate/Acetyl CoA

• NAD+

• FAD

• ADP + P

OUTPUTS of the Krebs Cycle

• NADH + FADH2 (used in ETC)

• CO2 (waste)

• 2 ATP (used for cellular processes)

Electron Transport Chain (ETC)

a series of protein complexes and molecules embedded in the inner mitochondrial/plasma membrane

• Major yield of energy comes from the transfer of electrons via ETC

• Oxygen is the final receptor

• Oxygen binds to hydrogen ions + electrons, ensuring the process continues without electrons building up

INPUTS of the ETC

• NADH + FADH2 (from glycolysis and krebs)

• ADP + P

• O2

OUTPUTS of the ETC

• 26 OR 28 ATP

• H2O

• NAD+

• FAD

Anaerobic Respiration

a.k.a: fermentation → allows cells to produce small amounts of ATP (via glycolysis) from glucose when there is no oxygen available

• Occurs entirely in the cytoplasm

Two types of Fermentation

lactic acid and alcoholic

Lactic Acid Fermentation

occurs in animal cells, some bacteria and molds

• Produces 2 ATP and lactate (lactic acid)

Alcoholic Fermentation

occurs in many yeasts + plants

• Produces 2 ATP, ethanol and CO2

Factors affecting the Rate of Cellular Respiration

• Glucose availability

• Oxygen concentration

• Temperature

Biomass

organic material of animal/plant origin, often sourced from a variety of industries

Fossil fuel

a fuel formed from dead organic material over millions of years

Carbon-neutral

a process that has no net release of CO2 into the atmosphere

Non-renewable

resources that are being used up at a faster rate than they are being used

Renewable

resources that are re-formed at the same or faster rate than they are being used

Fossil fuels

• Non-renewable as it takes millions of years to complete

• Rate of production is much lower than rate of consumption

• EXAMPLES: coal and oil

Biofuels

• Renewable as they continue supplying plant material/animal by-products indefinitely

• Better for the environment → carbon-neutral

• CO2 released during combustion is originally captured by plant during photosynthesis

• CO2 is cycled back into atmosphere as O2 and can be used again as an input

• No net increase in the amount of CO2 released in atmosphere

FIRST step of making Biofuel

Deconstruction

• Biomass is broken down so surface area increases (more efficient)

• Break cell wall + cellulose via biological, chemical and physical approaches

SECOND step of making Biofuel

Digestion by Enzymes

• Broken-down Biomass is exposed to enzymes (amylase)

  • Breaks down starch and cellulose

  • Converts into glucose + other sugars

• Hydrolysis → breakdown of polysaccharides aided by water

THIRD step of making Biofuel

Ethanol Fermentation

• Yeast used to facilitate anaerobic fermentation

• Large amount of ethanol produced

• Ethanol diffuses out of the yeast cells + harnessed for biofuel

FOURTH step of making Biofuel

Purification/dehydration

• Ethanol is distilled via removal of water

• Converting into biofuel

• Biofuel is purified + ready to be used as liquid fuel

Applications of Biofuel

• Transportation need → alt for traditional fuels (petrol/diesel)

• Energy generation → used as back-up power systems where emissions must be kept low (school/hospitals)

Implications of Biofuel

• Renewability of biomass as a fuel source

• Carbon neutrality of biomass consumption