4.1 Glycolysis

‘Cliff Climb’ Starter To reach the top of the cliff, describe 10 things you’ve learnt about ATP and energy

Learning Objectives Success Criteria Understand where glycolysis fits into the overall process of respiration Describe the main stages of glycolysis Describe the main products of glycolysis Compare the key stages of aerobic and anaerobic respiration Accurately describe the chemical reactions at each stage of glycolysis Make a model of the chemical changes that occur in glycolysis

GCSE Write down as much as you can remember from GCSE about respiration. You have 5 minutes.

GCSE Recap This is a chemical reaction. It occurs in every living cell. It is not breathing!!! There are two types: - Aerobic and Anaerobic. Aerobic requires oxygen. Anaerobic does not.

Key points about respiration from GCSE and AS Biology? All living cells respire. During respiration a chemical reaction occurs in which sugars are oxidised to release energy. Carbon dioxide and water are released during these reactions. Glucose enters cells by diffusion and facilitated diffusion. When there is a shortage of oxygen, muscles produce lactate in respiration.

Mitochondria consist of a double layer of membrane surrounding a central matrix. The inner membrane is folded to form cristae. Coenzymes are complex organic molecules that are used by enzymes to accept or donate molecules involved in a reaction. They are often referred to as ‘Helper’ molecules as they carry chemical groups or ions about, e.g. NAD removes H+ and carries it to other molecules. An electron is a negatively charged particle surrounding the nucleus of an atom. A proton is a positively charged particle found in the nucleus of an atom.

A2 Level Respiration Food = source of energy for all animals. Carbohydrates and fats store chemical energy. Energy is released in series of controlled reactions. This process is known as RESPIRATION. ATP is the product and this is the cells energy currency. Energy yielding reactions are coupled with energy requiring reactions. i.e. Muscle contraction

A2 Level Respiration C 6 H 12 O 6 + 6O 2 6CO 2 + 6H 2 O + 38 ATP Only an overview!! “Respiration is a series of reactions in which energy is transferred from organic compounds, such as carbohydrates, to the temporary energy store, ATP.”

Respiration The process of respiration can be split into 4 stages. 1. Glycolysis 2. Link reaction 3. Krebs Cycle 4. Electron Transport Chain In what part(s) of the cell does respiration take place?

The Powerhouse of the Cell Mitochondria Found in all cell types. Found in higher numbers in cells that have higher energy demands. 1µm diameter 10µm long.

Structure of a Mitochondrion

Outer membrane DNA Ribosomes Crista (fold in inner membrane) Stalked particles Matrix

What Happens Where? Glycolysis = Cytoplasm of the cell. Link reaction = Matrix of the mitochondria. Krebs cycle = Also in the matrix. Electron transfer chain Utilises proteins found in the membrane of the christa.

Glycolysis This is the 1 st stage. It occurs in the cytoplasm. It’s a splitting thing!

GLYCOLYSIS (carbohydrate splitting) First stage of aerobic respiration & anaerobic respiration. Doesn’t need O 2 – so this stage is anaerobic! Occurs in the cytoplasm of all living cells There are 2 stages of Glycolysis: 1) Phosphorylation 2) Oxidation

Glucose ATP ADP ATP ADP H2OH2O 4ATP 4H 2NAD + 2NADH + 2H + 4ADP 4P i Phosphorylation Hydrolysis Oxidation

Glucose Hexose phosphate Hexose bisphosphate 2X Triose phosphate 2X Pyruvate ATP ADP ATP ADP H2OH2O 4ATP 4H 2NAD + 2NADH + 2H + 4ADP 4P i Phosphorylation Hydrolysis Oxidation

Stage 1 - Phosphorylation Glucose is phosphorylated by adding 2 phosphates from 2 molecules of ATP. Glucose is split using water(hydrolysis). 2 molecules of triose phosphate are created and 2 molecules of ATP are used up.

Stage 2 - Oxidation 4 ATP are produced, but 2 were used at the start, so there’s a net gain of 2ATP. Coenzyme NAD + collects the hydrogen ions forming 2 Reduced NAD + (NADH + H + ) The triose phosphate is oxidised (loses hydrogen), forming 2 molecules of pyruvate.

Glycolysis You start with glycogen. Glucose (6C) 2 ATP 2 ADP Glyceraldehyde 3-phosphate (3C x 2) Pyruvate (3C x2) 4 ADP + 4Pi 4 ATP NADReduced NAD Nicotinamide adenine dinucleotide = So it gains electrons You finish with Pyruvate 2H x 2 Glycogen Why is Glycolysis termed anaerobic? What is the NET production of ATP? NAD+ + 2H  NADH + H+ (oxidised form ) (reduced form) NB Rather then write NADH, examiners often simply refer to it as reduced NAD or reduced coenzyme

The sums The end products of glycolysis are pyruvate and reduced NAD Energy is released during this reaction. 4 molecules of ADP + Pi converted to 4 molecules of ATP. So net gain of 2 molecules of ATP 2 pairs of hydrogen atoms produced 2 Molecules of pyruvate.

2 reduced NAD (NADH + H + ) 2 Pyruvate 2 ATP Products of Glycolysis

The Fate of Pyruvate! THIS DEPENDS ON THE AVAILABILITY OF OXYGEN!!!

Glycolysis - group task Referring to your textbook (pages 50-51) and information from the PowerPoint slides, work in 4 groups to model the chemical changes that occur in glycolysis: 1. Glucose activated by phosphorylation 2. Phosphorylated glucose split into triose phosphate 3. Oxidation of triose phosphate 4. Production of Pyruvate and ATP Now join the models together in the right order to summarise the key events of glycolysis

Learning Objectives Success Criteria Understand where glycolysis fits into the overall process of respiration Describe the main stages of glycolysis Describe the main products of glycolysis Compare the key stages of aerobic and anaerobic respiration Accurately describe the chemical reactions at each stage of glycolysis Make a model of the chemical changes that occur in glycolysis