Enzymes and Cellular Respiration Metabolism Enzymes and Cellular Respiration

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Metabolism Metabolism is the sum of all the chemical reactions in a cell Anabolism – Chemical reactions that build molecules by using available energy to form bonds Catabolism – Chemical reactions that break down larger molecules to release energy, making it available to do work

Enzymes Enzymes- Organic Catalysts Speed up reactions Lower the energy of activation Used but not used up Specific to a chemical reaction or substrate Substrates – the molecules acted on by enzymes End Products – The products of chemical reactions involving enzymes Names – “-ase” ending added to substrate or the reaction Lipase – breaks down lipids Deaminase – Removes an amine group (not all enzymes end in “-ase” – like trypsin)

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Active sites Certain critical areas of the enzyme that have a shape that matches the substrate of the reaction. Shape dictates function – therefore, if the shape of the active site changes, the function is altered. Enzymes are made of protein – therefore temperature and pH are critical conditions required for enzymatic functioning.

Energy and ATP Energy – the ability to do work Kinetic – energy in motion or of movement Potential – stored energy (gravitational, elastic, and chemical) Exergonic – energy released as a product (heat released) Endergonic – energy needed (a reactant in the chemical reaction) (heat absorbed) ATP – Adenosine TriPhosphate - Nucleotide containing: Adenine Ribose 3 Phosphates Calorie – unit of energy = amount of energy required to raise the temperature of 1 Kilogram of water 1° C. (nutritional Calorie = 1 Kilocalorie = 1000 calories). Capitalized C in Calorie – tells you that it is the Kilocalorie. When you say that a candy bar has 240 Calories, you are talking about the Kilocalorie. ATPase – enzyme that breaks down ATP – ATP  ADP + P ATP Synthase – enzyme that speeds up the production of ATP – ADP+P  ATP

Catabolism of Glucose Respiration – a series of biochemical reactions in which energy is liberated – then used to synthesize ATP. The overall reaction is exergonic – not all energy released is used to make ATP. Formula: C6H12O6 + 6O2  6CO2 + 6H2O + 36-38 ATP

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Overall Aerobic Respiration Reaction Steps: Glycolysis Transition Kreb’s Cycle (Tricarboxylic Acid – TCA cycle) (Citric Acid Cycle) Electron Transport Chain (Chemiosmosis)

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Glycolysis Location – Cytoplasm of both eukaryotic and Prokaryotic Reactants – Glucose (6 C sugar) molecule + 2 ATP (to prime the pump) Products: 2 NADH 4 ATP – therefore a Net of 2 ATP 2 Pyruvic Acid (3 C sugar)

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Fermentation If no oxygen is available – then the cell goes into Fermentation and various products are produced: Acids Alcohol Carbon dioxide

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Transition Transition – Considered part of the Kreb’s cycle Location – Cytoplasm Eukaryotic cells - it is transitioning into the mitochondria Prokaryotic cells - it is in cytoplasm Reactants – 2 Pyruvic Acid Products – 2 NADH, 2 CO2, 2 Acetyl Co-A (2 C Sugar)

Kreb’s Cycle Also called Tricarboxylic Acid and Citric Acid Cycle – for the recycled molecules in the cycle Location Matrix of mitochondria (Eukaryotic) Cytoplasm (Prokaryotic Cells) Reactants – 2 Acetyl Co-A Products – 6 NADH 2 FADH2 4 CO2 2 ATP

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Electron Transport Chain Also known as Chemiosmosis Series of oxidation (loses electrons oxidation) and reduction (gains electrons reduction) reactions will pass the electrons from carrier molecules to proton pumps – powering the movement of protons across the membrane into the inner membrane space (or periplasmic space in prokaryotes). Hydrogen ions build up in the “inner membrane space” – increasing the potential energy Hydrogen ion will move across the membrane through ATP synthase molecule – Producing high energy phosphate bonds in ATP Location – Inner membrane Space of Mitochondria (Eukaryotes) or Periplasmic Space (Prokaryotes) Reactants 6 Oxygen molecules – end electron receptor 10 NADH - Each NADH has enough potential energy to produce 3 ATP (except the 2 NADH in Eukaryotic Cells produced during Glycolysis – which only produce 2 ATP/NADH) 2 FADH2 - Each FADH2 has enough potential energy to produce 2 ATP Products 28-30 ATP produced from NADH and 4 ATP produced from FADH2 6 H2O

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Other Aspects of Catabolism Catabolism of other Carbohydrates (ie Starch) Hydrolysis – addition of water and specific enzymes for each carbohydrate (called hydrolases) will cause the decomposition of these carbohydrates Catabolism of Proteins and Fats - Hydrolysis

Anabolism of Carbohydrates Photosynthesis Energy + 6CO2 + 6H2O  C6H12O6 + 6O2 Using light from the sun to synthesize carbohydrates

Anabolism of Proteins Protein Synthesis Occurs in Ribosomes of Eukaryotics and Prokaryotics Removing water to form peptide bonds between carboxyl group and amine group of two different amino acids Transcription – making RNA from DNA code Translation – making Proteins from RNA Replication – making a copy of DNA for new cells during cell cycle