Nutrition and Metabolism Notes video 1

Nutrients

• Chemicals found in diet (food and drink).

• Aid in repair, growth, maintenance of cell/tissue function and anatomy.

• Two categories:

  • Macronutrients

  • Micronutrients

Macronutrients

• Needed in large amounts.

• Include:

  • Carbohydrates

  • Lipids

  • Proteins

  • Water

• Nucleic acids (DNA, RNA) are biomolecules but don't play a critical role in nutrition.

Micronutrients

• Needed in small amounts.

• Subdivided into:

  • Vitamins (organic)

  • Minerals (inorganic)

Vitamins

• Organic compounds for maintaining a healthy body

Water-Soluble Vitamins

• Easily transported through water.

• Easily eliminated if there's an excess.

• Include B vitamins and vitamin C.

• Most vitamin deficiencies are associated with these vitamins.

• Examples:

  • B1 (Thiamine): Critical to cellular respiration, helps make pyruvate.

  • B2 (Riboflavin): Makes FAD, critical to cellular respiration.

  • B3 (Niacin): Makes NAD, critical to cellular respiration.

  • B7 (Biotin): Affects metabolism of carbs, fats, and proteins.

  • B9 (Folic Acid): Helps with hematopoiesis (associated with iron), nucleotide production, and activating vitamin B12.

  • B12: Associated with intrinsic factor (made by gastric parietal cells), erythropoiesis, amino acid production, and acetylcholine production.

  • Vitamin C (Ascorbic Acid): Associated with the immune system, found in bright fruits/vegetables, aids wound healing, antioxidant, and builds collagen.

Fat-Soluble Vitamins

• Mixed with fat, lipophilic.

• Excesses (hypervitaminosis) usually due to these vitamins (A, D, E, K).

• Examples:

  • A (Retinol): Immune system, vision development, and reproduction.

  • D (Calciferol): Calcium and phosphorus absorption (GI Tract) and thus bone growth/maintenance; homeostasis of skin, liver, and kidneys.

  • E (Tocopherol): Protects plasma membranes, promotes wound healing, and inhibits scar tissue formation (fibrosis).

  • K (Phylloquinone): Produced by large intestine; used by liver to make clotting factors, contributes to bone health.

Minerals

• Inorganic elements/compounds for maintaining a healthy body.

• Subdivided into:

Major Minerals

• Required over 100 mg per day.

• Include: Calcium, phosphorus, potassium, sodium, chloride, magnesium.

• Examples:

  • Calcium: Bone/teeth structure, muscle contraction, blood pressure/clotting, neurotransmitter release.

  • Phosphorus: Bone/teeth structure, phospholipid production.

  • Potassium: Fluid/electrolyte balance, action potential repolarization.

  • Sodium: Action potential depolarization, fluid/electrolyte balance.

  • Chloride: pH balance, fluid balance (often found with sodium as salt).

  • Magnesium: Bone/teeth health, enzyme cofactor, muscle contraction, nerve transmission.

Trace Minerals

• Required less than 100 mg per day.

• Include: Iron, fluoride, iodine.

• Examples:

  • Iron: Needed for hemoglobin.

  • Fluoride: Hardens teeth.

  • Iodine: Used for thyroid hormones.

Adaptations and Metabolic Processes

Absorptive State

• Nutrients absorbed from diet (after consuming a meal).

• Regulated by insulin (from beta cells).

• Insulin's job is to reduce overall levels.

• Carbohydrates:

  • Build it into glycogen.

  • Build it into fat.

  • Build it into protein.

  • Use it for energy.

• Insulin increases absorption of carbs, fats, and amino acids into cells.

• Goal: Decrease blood glucose levels.

• Promotes:

  • Glycolysis (glucose breakdown).

  • Glycogenesis (glucose to glycogen).

  • Lipogenesis (conversion to fat for storage).

  • Protein synthesis.

• Inhibits gluconeogenesis (making new glucose from fats/proteins).

• Insulin prevents new glucose creation and favors utilizing existing glucose.

Post-Absorptive State (Fasting State)

• A few hours after a meal.

• Goal: Raise blood sugar to 90-100 mg/dL.

• Major hormone: Glucagon (from alpha cells).

• Promotes:

  • Glycogenolysis (glycogen breakdown).

  • Gluconeogenesis (generate new glucose).

  • Lipolysis (fat breakdown).

• Other hormones involved (sympathoadrenal system):

  • Epinephrine: Promotes glycogenolysis and lipolysis (short-term stress).

  • Cortisol: Promotes fat and protein metabolism & gluconeogenesis; glucocorticoid regulates glucose levels (long-term stress).

  • Growth Hormone: Produced when blood glucose drops or during prolonged fasting; raises blood glucose (needs fuel for growth).

Metabolism

• All chemical reactions in the body (building/breaking).

• Catabolism (Decomposition Reactions):

  • Breaks down complex molecules into monomers (e.g., proteins to amino acids, triglycerides to monoglycerides/fatty acids).

• Anabolism:

  • Combines simple molecules (monomers) into complex ones.

• Heat is released in both catabolic or anabolic reactions.

• Energy Flow: Fuel → catabolism → yields energy (captured as ATP) ↔ anabolism (requires energy).

Thermodynamics

• Laws governing energy movement and reactions.

First Law of Thermodynamics

• Energy cannot be created or destroyed in a closed system; it transforms (also applies to mass).

Second Law of Thermodynamics

• In a closed system, entropy (heat) increases with a spontaneous process.

• Energy conversion is not perfectly efficient; some energy is lost as heat.

Metabolic Rate

• Energy used by the body per unit time (e.g., kilocalories/day or hour).

• Measured using calorimeter or spirometer.

Basal Metabolic Rate (BMR)

• Minimum energy needed to survive (awake and relaxed state).

• Average BMR: 1,500-2,000 kilocalories per day.

Kilocalories

• Food calories (Calorie with a capital C).

• Carbs/Proteins: 4
  ewline \frac{kilocalories}{gram}

• Fats: 9 \frac{kilocalories}{gram}

Nutrition Labels

Serving Size

• Amount typically eaten at one time

Calories

• Energy in a single serving.

Total Fat

• Includes saturated, unsaturated, & trans fats.

• Unsaturated Fats: Oils, nuts, avocados (fluid at room temp).

• Saturated Fats: Cheeses, sausages, dairy products (moderation is key).

Trans Fats

• Partially hydrogenated oils (unhealthy), preservatives that extend shelf life.

• Difficult for body to process, gums up processes, and causes fat buildup.

Sodium

• American Heart Association recommends about 1500 \frac{mg}{day}.

Carbohydrates

• Starches, sugars, fibers.

• Dietary fiber promotes digestion & satiety.

Protein

• Needed for cell structure & satiety.

Percent Daily Value

• Recommended nutrient amount based on a 2,000 kilocalorie/day diet.

• Rounding: 0 grams can mean up to 0.49 grams (e.g., Tic Tacs' sugar content).

Dietary Guidelines

• Food Pyramid: Kellogg's Corporation influenced (pushed cereal/grains).

• MyPlate: Government-issued diet plan.

  • 50-60% carbs (less than 50% simple sugars).

  • Less than 30% fat (no more than 10% saturated).

  • 12-15% proteins.

Caloric Expenditure Examples

• Aerobics:

  • 419 \frac{kilocalories}{hour}

Factors Influencing Metabolic Rate

• Body Size: Larger size needs higher BMR.

• Physical Activity: Increases BMR (initially), then may decrease with acclimation.

• Mental State: Stress can increase BMR; depression can decrease it.

• Absorptive Status: Absorptive state decreases BMR; post-absorptive increases BMR.

• Thyroid Hormones (T3/T4): Increase BMR; they require iodine.

• Age: BMR tends to decrease with age; children have high BMR for growth.

• Drugs: Antidepressants & steroids can increase body mass and decrease BMR. Caffeine & nicotine can increase BMR.

• Environmental Factors: Cold or warm environments increase BMR (thermoregulation).

Thermoregulation

• Regulated by hypothalamus (preoptic area acts as thermostat).

Heat-Loss Center

• Promotes cutaneous vasodilation and sweating, inhibits heat-promoting center.

Heat-Promoting Center

• Conserves and generates heat.

  • Vasoconstriction in the skin.

  • Shivering thermogenesis (muscle contraction uses ATP to generate heat).

  • Non-shivering thermogenesis (raises metabolic rate).

  • Behavioral thermoregulation (adding/removing clothes)

Enzymes

• Biological catalysts speed up reactions by decreasing activation energy

• Enzyme Structure:

  • Holoenzyme: Complete, functional enzyme.

  • Active Site: Where substrate binds to perform reaction for product.

  • Apoenzyme: Protein portion of holoenzyme (without substrate, coenzymes or cofactors).

  • Cofactors: Inorganic materials aiding in the process (e.g., magnesium).

  • Coenzymes: Organic molecules aiding in the process (e.g., vitamins B2/B3).

Coenzymes

• Organic molecules (often vitamin-derived) aiding in reactions.

Examples:

• NAD (Nicotinamide Adenine Dinucleotide): Reduced to NADH, electron carrier in cellular respiration.

• FAD (Flavin Adenine Dinucleotide): Becomes FADH2, electron carrier in Kreb's cycle (citric acid).

• Coenzyme A: Prepares pyruvate to enter mitochondria by forming acetyl CoA.

Oxidation and Reduction

Oxidation

• Reaction that removes electrons (and protons/hydrogens) from an atom/molecule.

• Catabolic

Reduction

• Reaction that gains electrons (and protons/hydrogens).

• Anabolic

Coupled Reactions

• Oxidation and reduction occur together (one molecule loses electrons while another gains them).

• Electron carriers (NAD, FAD) help transfer electrons.

Carbohydrate Metabolism

• Mostly glucose use.

  • Amylase enzymes breakdown starches.

  • Disaccharidases such as sucrase, maltase, and lactase break down disaccharides.

• Glucose Use:

  • ATP production (if energy is low).

  • Amino acid synthesis.

  • Glycogen synthesis (storage in liver/muscles).

  • Triglyceride conversion (excess carbohydrates stored as fat in adipose tissue).

Glucose entry into cells

• Requires facilitated diffusion via GLUT (glucose transporter) molecules.

• Insulin binds to receptors, activating GLUT transporters to move to the cell membrane, allowing glucose to enter.

• Damaged GLUT transporters or insulin receptors cause hyperglycemia (Type 2 Diabetes).

Cellular Respiration

• Gas exchange, breakdown of glucose to make energy.

Anaerobic Respiration

• Breaks glucose without oxygen; inefficient.

• Byproduct: ATP and lactic acid (in humans) or alcohol (in bacteria).

Aerobic Respiration

• Uses oxygen to break down glucose (more efficient).

• Four stages:

  • Glycolysis.

  • Formation of Acetyl Coenzyme A (Prep step).

  • Krebs Cycle (Citric Acid Cycle).

  • Electron Transport Chain.

Glycolysis

• Glyco=sugar + lysis=break

• Breaks down a 6-carbon sugar to release ATP, NADH, and pyruvate acid.

• Phases:

  • Investment Stage: Using 2 ATP, phosphorylate the sugar.

  • Oxidation/Splitting: Split sugar into 2, 3-carbon sugars.

  • Energy Harvest: Remove phosphates, yielding 4 ATP (net gain = 2 ATP), 2 pyruvate, 2 NADH.

• Enzymes: Kinases (phosphorylation) and Isomerases (change shape).

Glycolysis Visualized

• Starts off with glucose, becomes two pyruvate, two NADH, and a net of two ATP

Fermentation

• Anaerobic pathway after glycolysis.

• Regenerates NAD+ for further glucose breakdown.

• Oxidizes NADH to NAD+ and reduces pyruvate to lactate (in humans).

• Lactic acid buildup can cause metabolic acidosis.

Preparatory Step (Decarboxylation)

• Occurs if oxygen is present, transitioning pyruvate towards mitochondria.

• Pyruvate dehydrogenase decarboxylates pyruvate (removes carbon dioxide).

• Forms Acetyl CoA (acetyl group + coenzyme A) for entry into mitochondrial matrix, to begin Citric Acid Cycle.

Krebs Cycle (Citric Acid Cycle)

• Occurs in mitochondrial matrix.

• Forms 2 citric acids from each glucose

• Yields: 2 ATP, 2 FADH2, 4 carbon dioxide, 6 NADH.

• All 6 Carbon dioxides created from glucose

Electron Transport Chain

• Consists of cytochromes: proteins in membrane that accept electrons.

• Each carrier (NADH and FADH2) gives electrons to these proteins.

• Proteins move the electrons, activating proton pumps building up hydrogen ions.

• Oxygen: Final electron acceptor, forming water.

  • Electrons bind to Hydrogen ions along with oxygen atoms to form water.

• Hydrogen ions return through ATP synthase (generating about 38 ATP after two cycles of Krebs and all NADH and FADH molecules).

\text{Glucose} +\text{Oxygen} + ADP+\text{Phosphate} \rightarrow 6 \text{Carbon Dixoide} + 6 \text{Water} + 30-32 \text{ATP}

Other Metabolic Reactions

Glycogenesis

• Excess glucose is turned into glycogen for storage, in the liver and muscles

Glycogenolysis

• Where existing glycogen stores are broken down for use as fuel

Gluconeogenesis:

• Making new glucose from fats or other carbohydrates.

Lipogenesis

Formation of lipids from excess carbs. Can create glycerol and triglycerides. All in adipose tissue

Lipolysis

Oxidation of glycerol and fatty acids from triglycerides through fatty acids. Glycerol can be put into glycolysis from here

Lipid Transport

*Chylomicrons: Carry dietary lipids in adipose tissue
*Very low proteins (VLDL): Transport triglycerides from hepatocytes to adipocytes
*Intermediate Protein: Muscle/Adipose removal + cholesterol addition
Low Dentsity Lipoproteins (LDL): Moves 75% of cholesterol from liver into cells. Can create plaques
High Density Lipoproteins (HDL): Good cholesterol, excess cholesterol into liver