Cell Respiration

Cellular Respiration To perform their many tasks cells require transfusions of energy from outside sources To perform their many tasks cells require transfusions of energy from outside sources Energy enters ecosystems as sunlight, the energy source for plants and other photosynthetic organisms Energy enters ecosystems as sunlight, the energy source for plants and other photosynthetic organisms Animals obtain energy by eating plants or by eating organisms that eat plants Animals obtain energy by eating plants or by eating organisms that eat plants

Cellular Respiration During cellular respiration organic compounds are broken down using oxygen as a reactant During cellular respiration organic compounds are broken down using oxygen as a reactant Organic compounds + oxygencarbon dioxide + water + energy

Cellular Respiration Respiration is a stepwise redox (reduction/oxidation) reaction Respiration is a stepwise redox (reduction/oxidation) reaction Recall: a redox reaction is a transfer of one or more electrons from one reactant to another Recall: a redox reaction is a transfer of one or more electrons from one reactant to another C 6 H 12 O 6 + 6O 2 6CO 2 + 6H 2 O + energy Cellular Respiration: Na + Cl 2 NaCl reduction oxidation reduction

Cellular Respiration Energy is not liberated all at once (explosion!) Energy is not liberated all at once (explosion!) Glucose is broken down gradually Glucose is broken down gradually Hydrogen atoms and electrons are stripped from glucose and are passed to a coenzyme called nicotinamide adenine dinucleotide (NADH) Hydrogen atoms and electrons are stripped from glucose and are passed to a coenzyme called nicotinamide adenine dinucleotide (NADH) Eventually electrons are passed to oxygen in a series of steps called the electron transport chain Eventually electrons are passed to oxygen in a series of steps called the electron transport chain

NAD + is an oxidizing agent C OH + NAD + C O + NADH Oxidized form Reduced form

Three Stages of Respiration The three main stages are: The three main stages are: 1) Glycolysis 2) Krebs cycle (citric acid cycle) 3) electron transport and oxidative phosphorylation Glycolysis takes place in the cytoplasm Glycolysis takes place in the cytoplasm Krebs cycle and electron transport take place in the mitochondria Krebs cycle and electron transport take place in the mitochondria

Mitochondria  Found in nearly all eukaryotic cells  In animal cells they are oval  Cristae increase surface area and are the site of electron transport  The matrix is like the cytoplasm of cells where enzymatic reactions take place

The first stage of respiration Glycolysis

Respiration Process of respiration is split into three stages and the link reaction Process of respiration is split into three stages and the link reaction

Glycolysis is the first stage of respiration!

Glycolysis splits one molecule of glucose into two smaller molecules of pyruvate

Glycolysis is the first stage of respiration! Glycolysis splits one molecule of glucose into two smaller molecules of pyruvate Glucose is a hexose (6-carbon) molecule

Glycolysis is the first stage of respiration! Glycolysis splits one molecule of glucose into two smaller molecules of pyruvate Glucose is a hexose (6-carbon) molecule Pyruvate is a triose (3-carbon) molecule

Glycolysis is the first stage of respiration! Glycolysis splits one molecule of glucose into two smaller molecules of pyruvate Glucose is a hexose (6-carbon) molecule Pyruvate is a triose (3-carbon) molecule Pyruvate is also known as pyruvic acid

Glycolysis takes place in the cytoplasm of cells.

It’s the first stage of both aerobic and anaerobic respiration.

It doesn’t need oxygen to take place – so it’s anaerobic

It’s the first stage of both aerobic and anaerobic respiration. It doesn’t need oxygen to take place – so it’s anaerobic

There are TWO STAGES of GLYCOLYSIS – Phosphorylation and Oxidation

Glycolysis

Stage One - Phosphorylation

1.Glucose is phosphorylated by adding 2 phosphates from 2 molecules of ATP to give a hexose phosphate.

Stage One - Phosphorylation 1.Glucose is phosphorylated by adding 2 phosphates from 2 molecules of ATP to give a hexose phosphate. 2.The hexose phosphate is split using water

Stage One - Phosphorylation 1.Glucose is phosphorylated by adding 2 phosphates from 2 molecules of ATP to give a hexose phosphate. 2.The hexose phosphate is split using water (hydrolysis)

Stage One - Phosphorylation 1.Glucose is phosphorylated by adding 2 phosphates from 2 molecules of ATP to give a hexose phosphate. 2.The hexose phosphate is split using water (hydrolysis) 3.2 molecules of triose phosphate and 2 molecules of ADP are created.

A triose phosphate is just a simple 3-carbon sugar with a phosphate group attached. Different books use different names!

Glyceraldehyde 3- phosphate (G3P)

What’s the point? Glucose can now no longer leave the cell. Glucose can now no longer leave the cell.

What’s the point? Glucose can now no longer leave the cell. Glucose can now no longer leave the cell. Molecules produced are much more reactive! Molecules produced are much more reactive! Glyceraldehyde 3- phosphate

Stage Two - Oxidation

1.The triose phosphates are oxidised (lose oxygen), forming two molecules of pyruvate.

Stage Two - Oxidation 1.The triose phosphates are oxidised (lose oxygen), forming two molecules of pyruvate. 2. Coenzyme NAD + collects the hydrogen ions, forming 2 reduced NAD (NADH + H + )

Stage Two - Oxidation 1.The triose phosphates are oxidised (lose oxygen), forming two molecules of pyruvate. 2. Coenzyme NAD + collects the hydrogen ions, forming 2 reduced NAD (NADH + H + ) A coenzyme is a helper molecule that carries chemical groups or ions, e.g. NAD + removes H + and carries it to other molecules.

Stage Two - Oxidation 1.The triose phosphates are oxidised (lose oxygen), forming two molecules of pyruvate. 2. Coenzyme NAD + collects the hydrogen ions, forming 2 reduced NAD (NADH + H + ) 3. 4 ATP are produced, but 2 were used up at the beginning, so there’s a net gain of 2 ATP.

Next in Aerobic respiration….

1.The 2 molecules of reduced NADH go to the electron transport chain (ETC), part 4 of respiration.

Next in Aerobic respiration…. 1.The 2 molecules of reduced NAD go to the electron transport chain (ETC), part 4 of respiration. 2. The two pyruvate molecules go into the matrix of the mitochondria for the link reaction.

The Link Reaction

The second stage of respiration

You are now in the matrix of the mitochondria!

Link Reaction – 2 nd stage of respiration

The Link Reaction converts Pyruvate to Acetyl Coenzyme A

Link Reaction – 2 nd stage of respiration The Link Reaction converts Pyruvate to Acetyl Coenzyme A The link reaction happens when oxygen is available.

Link Reaction – 2 nd stage of respiration

1.One carbon atom is removed from pyruvate in the form of CO 2.

Link Reaction – 2 nd stage of respiration 1.One carbon atom is removed from pyruvate in the form of CO 2. 2.The remaining 2-carbon molecule combines with coenzyme A to produce acetyl coenzyme A (acetyl CoA).

Link Reaction – 2 nd stage of respiration 1.One carbon atom is removed from pyruvate in the form of CO 2. 2.The remaining 2-carbon molecule combines with coenzyme A to produce acetyl coenzyme A (acetyl CoA). 3.Another oxidation reaction happens when NAD + collects more hydrogen ions. This forms reduced NAD (NADH + H + ).

Link Reaction – 2 nd stage of respiration 4. No ATP is produced in this reaction.

Link Reaction – 2 nd stage of respiration The Link reaction happens Twice for every Glucose Molecule

Link Reaction – 2 nd stage of respiration The Link reaction happens Twice for every Glucose Molecule So for every glucose molecule used in glycolysis, two pyruvate and two acetyl CoA molecules are made.

So for each glucose molecule:

Two molecules of acetyl CoA go into Krebs cycle (part 3 of respiration)

So for each glucose molecule: Two molecules of acetyl CoA go into Krebs cycle (part 3 of respiration)

So for each glucose molecule: Two molecules of acetyl CoA go into Krebs cycle (part 3 of respiration) Two carbon dioxide molecules are released as a waste product of respiration

So for each glucose molecule: Two molecules of acetyl CoA go into Krebs cycle (part 3 of respiration) Two carbon dioxide molecules are released as a waste product of respiration Two molecules of reduced NAD are formed and go into the electron transport chain (part 4 of respiration)

So for each glucose molecule: Two molecules of acetyl CoA go into Krebs cycle (part 3 of respiration) Two carbon dioxide molecules are released as a waste product of respiration Two molecules of reduced NAD are formed and go into the electron transport chain (part 4 of respiration)