Ch. 4 and 18 Cellular Metabolism and Nutrition

Metabolism Metabolism - Sum total of chemical reactions within a cell. –All of the chemical reactions within your body.

2 Types of Metabolic Reactions Anabolism - (anabolic metabolism) - Metabolic process by which larger molecules are synthesized from smaller ones. –Dehydration synthesis Joining monosaccharide to form polysaccharides (glycogen). Joining glycerol and fatty acids to form fat molecules. Joining amino acids to form proteins.

2 Types of Metabolic Reactions Continued Catabolism - (catabolic metabolism) - Metabolic process that breaks down large molecules into smaller ones. –Hydrolysis Breaking down complex carbohydrates into monosaccharides. Breaking down fats into glycerol and fatty acids. Breaking down proteins into amino acids.

Anabolism Molecules made or broken down by these processes Catabolism Building molecules Glycogen, Fat molecules Proteins Breaking down molecules EX: Dehydration Synthesis Ex: Hydrolysis Forms molecules while releasing Water Breaks down molecules while splitting or using water.

Metabolism Animation

Enzyme Action Enzymes are special proteins that catalyze chemical reactions in the body. –They are highly specific. –The substances that they work on are called substrates. –Substrates bind at the enzymes active site.

Enzyme catalysis Substrate + enzyme  Enzyme substrate complex  Product (changed substrate)  Enzyme (unchanged)

Enzyme Catalysis Speed of the enzyme action depends on the concentration of the enzyme and substrate. –As enzyme concentration increases, substrate activity will increase to a point. –As substrate concentration increases, enzyme activity will increase to a point.

Metabolic Pathways Sequences of enzyme controlled reactions that lead to the synthesis or breakdown of particular biochemicals.

Coenzymes Coenzymes are non-protein substances (such as vitamins) that either aid in enzyme activity, or are required for the enzyme to function properly.

Factors that Affect Enzyme Activity Excessive temperatures (too hot or too cold) Radiation Electricity Certain Chemicals Extreme pH values

Factors that Affect Enzyme Activity Continued If the enzyme becomes denatured, it will no longer work. –Ex. Frying an egg The active site is no longer functional.

Lactose Intolerance

Energy for Metabolic Reactions Energy - the capacity for doing work. ATP - energy rich molecule in cells that powers cellular activities.

ATP ATP consists of 3 parts – a sugar (ribose) – a base (adenine) – 3 phosphate groups Energy is stored in the bonds that hold the phosphates together.

ATP To release the stored energy, the last phosphate is removed and ADP (adenosine diphosphate) + a phosphate group is formed.

ATP Energy from cellular respiration is used to synthesize more ATP by adding the phosphate group back to ADP - This is known as phosphorylation.

Cellular Respiration The process that releases energy from molecules of glucose and makes it available for cellular use. (In the form of ATP). Includes 2 pathways –Aerobic - requires oxygen. –Anaerobic - no oxygen required.

3 Stages of Cellular Respiration Glycolysis - happens in the cytoplasm. (1st stage for aerobic and anaerobic reactions.) Citric Acid Cycle (Kreb’s Cycle) - happens in mitochondria. (aerobic only) Electron Transport chain - happens in the mitochondria. (aerobic only)

3 Stages of Cellular Respiration Glycolysis- happens in the cytoplasm. (1st stage for aerobic and anaerobic reactions.) The 6-carbon glucose is broken down into 3-carbon pyruvic acid molecules.

3 Stages of Cellular Respiration Citric Acid Cycle (Kreb’s Cycle)- happens in mitochondria. (aerobic only) The 3-carbon pyruvic acids enter the mitochondria and lose a carbon generating CO 2 and is combined with a coenzyme to form 2-carbon acetyl coenzyme A. Each of those combines with a 4- carbon oxaloacetic acid to form a 6-carbon citric acid.

3 Stages of Cellular Respiration Electron Transport chain- happens in the mitochondria. (aerobic only) The high energy electrons that were released during two previous cycles are carried and combined with enzymes that convert most of the remaining energy to ATP.

Aerobic vs. Anaerobic Respiration CharacteristicAerobic RespirationAnerobic Respiration Starting materialsGlucose 1 st stepGlycolysis Uses oxygen YesNo Cell locationCytoplasm then mitochondria Cytoplasm only ProductsWater and CO 2 Lactic Acid Number of ATP produced 38 ATP4 ATP Net Gain36 ATP2 ATP

Aerobic vs. Anaerobic Respiration Gb2EzF_XqAhttp:// Gb2EzF_XqA

Nutritional Requirements Carbohydrates Energy stored in their chemical bonds used to power cellular processes. Sources include: –Polysaccharides - grains, vegetables, meat. –Disaccharides - milk sugar, cane sugar, molasses. –Monosaccharides - fruit and honey. Requirements - at least grams daily. –Will differ based upon activity level.

Nutritional Requirements Lipids Supply energy and help build cellular structures. Sources include: –Triglycerides: plant and animal based foods. Saturated fats - mainly animal origin - meat, eggs, milk, lard, (coconut and palm oil) Unsaturated fats - plant origin - seeds, nuts, and plant oils. Requirements - Not more than 30% of daily calorie intake should come from fat.

Nutritional Requirements Proteins Amino acids from dietary proteins are used to form new proteins such as enzymes. Can be used to supply energy. Sources include: –Meat, fish, poultry, cheese, nuts, eggs, cereal. –We cannot synthesize 8 amino acids needed to build proteins, therefore we must get these from our diet. These are essential amino acids. Requirements: –About 0.8 grams per kilogram of body weight.

Nutrition Lectures 123/lecture-3#ch4 lecture 3, part 5http://oyc.yale.edu/psychology/psyc- 123/lecture-3#ch4 utritionFreeLecture.aspxhttp:// utritionFreeLecture.aspx