2.4 Cellular Respiration and ATP

Cellular respiration

The chemical process that releases energy inside cells

What cells need energy for

• Movement

• Growth and repair

• Active transport

• Keeping the body warm

The difference between respiration and breathing

Respiration happens inside the cells while breathing supplies oxygen

ATP

It comes from the food eaten and provides most of the energy that the cells require for cellular activity

Full meaning of the acronym ATP

Adenosine Triphosphate

Composition of ATP

1 adenosine molecule and 3 phosphate groups

How ATP works

• It stores energy in the mitochondria of the cells

• The ATP then leaves the mitochondria to release the stored energy

• This then enables cellular activity

Can cells function without ATP

No

Aerobic respiration

A type of cellular respiration that requires oxygen

Function of aerobic respiration

It produces a net yield of 36 to 38 ATP molecules, per molecule of glucose

Why we need oxygen

Because anaerobic respiration does not produce enough energy to keep us alive.

Process of aerobic respiration

• Glycolysis occurs, which is a process where by a glucose molecule is split in half within the cytoplasm to form two molecules of pyruvate.

• Pyruvate then moves into the mitochondria.

• In the presence of oxygen, it is fully broken down via the Krebs cycle and the electron transport chain

• This is done to produce a large volume of ATP, alongside carbon dioxide and water as waste products.

Aerobic respiration produces ______ stored in the bonds of ATP

energy

The written equation for aerobic respiration

Glucose + Oxygen = Carbon Dioxide + Water + energy

Where aerobic respiration occurs

It occurs in the cytoplasm and mitochondria

The waste products of aerobic respiration

CO₂ and water

Anaerobic respiration

A type of cellular respiration that does not require oxygen.

Function of anaerobic respiration

It produces 2 ATP molecules, per molecule of glucose

Process of anaerobic respiration

• Glycolysis occurs, which is a process where by a glucose molecule is split in half within the cytoplasm to form two molecules of pyruvate.

• Because oxygen is absent or in short supply, the pyruvate cannot move into the mitochondria.

• Instead, the pyruvate stays in the cytoplasm and is converted directly into lactic acid.

• This is done to produce a very small volume of ATP (only 2 ATP), alongside lactic acid as a toxic waste product that causes muscle fatigue.

The written equation for anaerobic respiration

Glucose —> Lactic Acid + energy

Where anaerobic respiration occurs

It occurs in the cytoplasm

The waste products of anaerobic respiration

Lactic acid

What the lactic acid does during anaerobic respiration

It builds up in the muscles causing pain and tiredness, leading to cramps.

When does anaerobic respiration occur

When the body's demand for energy is higher than the oxygen supply available to the cells. For example; during hard exercise like sprinting, weightlifting etc.

Cytoplasm

The thick, jelly-like liquid that fills the inside of a living cell, holding all the cell’s tiny working parts (organelles) in place.

The function of oxygen in cellular respiration

It acts as a final electron acceptor in the electron transport chain during cellular respiration, which allows cells to efficiently produce usable energy.