Nutrition and Energy Flow in Animals

Introduction to Nutrition

Nutrition is the process by which organisms obtain and utilize food for maintenance, growth, reproduction, and health. It involves the interaction of food with the organism, including finding, capturing, eating, digesting, absorbing, metabolizing, and eliminating nutrients.

• Essential nutrients: Nutrients that organisms cannot synthesize and must obtain from their diet.

• Types of essential nutrients:

  • Amino acids (some)

  • Fatty acids (some)

  • Vitamins (some)

  • Minerals (nearly all)

• Nutrients provide essential components for cellular processes required for maintenance, growth, and survival.

Elements in the Human Body

Elements are the basic building blocks of matter in living organisms. The human body is composed of several key elements, each with specific functions.

Plants and Animals: Source of Elements

• Carbon, hydrogen, and oxygen compounds primarily come from plants.

• Molecules: Carbon and other elements combine to form simple to complex organic molecules.

Hydrocarbons

Hydrocarbons are organic molecules consisting only of carbon and hydrogen. They serve as energy sources and structural components in living organisms.

• Can be combusted as a source of energy (oil and gasoline).

• Many organic molecules, such as fats, have hydrocarbon components.

• Hydrocarbons can undergo reactions that release a large amount of energy.

Minerals

Minerals are inorganic nutrients required in small quantities for normal function. They are essential for processes such as blood formation, bone and teeth structure, nerve function, and enzyme activity.

• Examples: Calcium, sodium, potassium, copper, iodine.

• Some minerals have a 'sweet spot'—too high or too low is not good.

• Other effects: Sodium increases blood pressure; copper can be toxic to sheep.

Vitamins

Vitamins are organic nutrients required in small quantities for normal function. Most cannot be synthesized by the organism and must be obtained from the diet.

• Water-soluble: B, C (excreted in urine if excess)

• Fat-soluble: A, D, E, K (stored in tissues, excess can be toxic)

• Some require minerals to function (e.g., Vitamin E + Selenium)

Macromolecules in Biology

Carbohydrates

Carbohydrates are organic molecules composed of carbon, hydrogen, and oxygen. They serve as a primary energy source for living organisms.

• General formula:

• Monosaccharides: Simple sugars (e.g., glucose )

• Polysaccharides: Complex carbohydrates (e.g., starch, glycogen, cellulose)

• Storage polysaccharides: Starch (plants), glycogen (animals)

• Structural polysaccharides: Cellulose (plants), chitin (arthropods)

Lipids

Lipids are hydrophobic molecules that include fats, oils, and steroids. They are important for energy storage, cell membrane structure, and hormone production.

• Fats: Glycerol + 3 fatty acids = lipid

• Unsaturated fatty acids: Double bonds, found in plant and fish oils

• Omega-3 fatty acids: Essential for humans, found in fish and eggs

• Steroids: Carbon skeleton in rings, precursor for hormones

Proteins

Proteins are large, complex molecules made up of amino acids. They perform a wide variety of functions in cells, including catalyzing reactions, providing structure, and regulating processes.

• Made up of 20 different amino acids

• Folded structure determines function

• Examples: Enzymes, antibodies, transport proteins

Amino Acids

Amino acids are the building blocks of proteins. They have non-polar (hydrophobic) and polar (hydrophilic) side chains, allowing for diverse protein structures.

• 20 amino acids to choose from

• Long chains form proteins

• Possible combinations are vast

Nucleic Acids

Nucleic acids (DNA and RNA) store and transmit genetic information. The sequence of nucleotides determines the proteins coded for and the biological activity of genes.

• DNA: AGCT (adenine, guanine, cytosine, thymine)

• RNA: AGCU (adenine, guanine, cytosine, uracil)

• Order of nucleotides determines protein coded for

• DNA forms a helix due to nucleotide interactions

Cellular Respiration and Energy Production

Overview of Cellular Respiration

Cellular respiration is the process by which cells convert macromolecules and oxygen into energy (ATP). It involves several key steps and produces ATP, the energy currency of the cell.

• Fuel (macromolecules) + oxygen delivered to cell via bloodstream

• Glycolysis:

• Acetyl CoA formation

• Citric acid cycle

• Oxidative phosphorylation, electron transport

• ATP production via H+ turbine

Glycolysis

Glycolysis is the first step in cellular respiration, where glucose is broken down in the cytosol to produce ATP and pyruvate.

• Initial investment: 2 ATP

• Steps 1-4: Investment phase

• Steps 6-10: Payoff phase, 4 ATP produced

• Takes place in the cytosol, outside the mitochondria

Pyruvate Oxidation

Pyruvate produced from glycolysis moves into the mitochondria, where it is converted to Acetyl CoA and NADH is produced.

• Requires oxygen and B vitamins

• Oxidation involves electron transfer and energy release

Citric Acid Cycle

The citric acid cycle (Krebs cycle) is a series of chemical reactions used by all aerobic organisms to generate energy.

• Produces: NADH, NADH, ATP, FADH2, NADH

Summary Table: Major Nutrients and Their Functions

Additional info:

• Ruminants (e.g., cows) and hindgut fermentors (e.g., horses) have specialized digestive systems for processing plant material.

• Understanding concepts is emphasized over memorization for exams.