Cellular Respiration Overview

Cellular Respiration

• Photosynthesis combines carbon dioxide, water, and solar energy to produce glucose, oxygen, and water.
• ATP (adenosine triphosphate) is a form of energy used by all cells. It contains three phosphate groups, a ribose sugar, and an adenine molecule (a nitrogenous base).
• Aerobic respiration produces large amounts of energy (ATP) from glucose, oxygen, and carbon dioxide.
  • The process occurs in stages.
  • Stage 1, glycolysis, happens in the cytoplasm and doesn't need oxygen.
    • Glucose is split into two pyruvic acid molecules (pyruvates).
  • Stage 2 happens in the mitochondria.
    • Pyruvates and oxygen produce carbon dioxide, water, and ATP.
    • Mitochondria have lots of folds to maximise surface area for greater ATP production. This is important for cells that need more energy (e.g., muscle cells).
• Anaerobic respiration (fermentation) produces less energy than aerobic respiration.
  • It produces ethanol, carbon dioxide, and ATP.
  • It happens in the cytoplasm of single-celled organisms like yeast and bacteria.
  • It is used in making breads, wine, beer, and soy products.

Digestion and Essential Nutrients

• The digestive system breaks down complex organic materials into simpler components for the body.
• The four components of digestion are ingestion, digestion, absorption, and egestion.
• Six essential nutrients for a healthy diet include carbohydrates, proteins, lipids, liquids, water, vitamins, and minerals.
• Proteins are complex molecules composed of amino acids and are important for building human proteins. They also provide energy.
• Carbohydrates are the main energy source for the body.
  • Monosaccharides are simple sugars (e.g., glucose, fructose).
  • Disaccharides are two simple sugars joined together.
  • Polysaccharides are complex carbohydrates made of many simple sugars (e.g., starch).

Fats, Lipids, Vitamins, and Minerals

• Lipids (fats and oils) are a concentrated energy source and are components of cell membranes. Fats and oils are made up of three fatty acids bonded to a glycerol molecule (forming a triglyceride).
• Vitamins are compounds needed in small amounts to perform many bodily functions. They are divided into fat-soluble and water-soluble.
• Minerals are naturally occurring elements essential for bodily processes and maintaining tissues (e.g., calcium for bones, iron for blood).

Digestion Path

• In the mouth, physical digestion (chewing) starts. Chewing forms a bolus.
• Saliva contains amylase, which breaks down carbohydrates, and also moistens and lubricates food.
• Food particles dissolve to stimulate taste buds on the tongue. Food is broken down in the mouth by teeth. Different types of teeth have different tasks (cutting, tearing, grinding).
• The esophagus uses rhythmic contractions called peristalsis to move food down to the stomach.
• The stomach is a place for food storage and initial protein digestion.
• Gastric fluids include mucus, stomach acid (HCl), and pepsinogen (which turns to pepsin, an enzyme that digests proteins).

Further Digestion in The Stomach and Small Intestine

• Peristalsis moves food through the gastrointestinal tract.
• The stomach stores food and digests proteins using gastric fluids.
• The small intestine is where most chemical digestion and absorption occur.
• Enzymes from the pancreas and small intestine break down carbohydrates, proteins, and lipids.
• Bile salts from the liver break down fats.
• Disaccharidases break down disaccharides in the small intestine.
• Lipases break down lipids into fatty acids and glycerol.