Biological Molecules, Nutrition, and Digestion Flashcards

Flashcards covering key vocabulary terms from the lecture notes on biological molecules, nutrition, and digestion.

Organic molecules

Molecules that contain carbon and hydrogen atoms, often found in living organisms.

1. Carbohydrates; Monomer, main function, food source, energy role, extra

• Monomer: Monosaccharides (e.g. glucose)

• Main Function:

  • Primary energy source (quick-release energy)

  • Some used for structural support (e.g. cellulose in plants)

• Food Sources:

  • Starch: Rice, potatoes, bread, cereals

  • Sugars: Fruit (natural), soft drinks, desserts (refined)

• Energy Role:

  • Short-term energy

  • Stored as glycogen in animals, starch in plants

  • 4 kcal/g

• Other Notes:

  • Simple sugars = fast energy, cause spikes

  • Complex carbs = slow-release energy (healthier)

Lipase how made, main function, food source, energy role, other notes

• Formed by the condensation of three fatty acid molecules with one glycerol molecule.

• Fats (solid at room temperature) and oils (liquid at room temperature) are insoluble in water, excellent for energy storage and forming barriers between watery environments.

• Main Function:

  • Long-term energy storage

  • Insulation (electrical & thermal)

  • Cell membranes (phospholipids)

  • Hormones (e.g. sex hormones from cholesterol)

• Food Sources:

  • Saturated fats: Meat, cheese, butter

  • Unsaturated fats: Nuts, sunflower seeds, plant oils

• Energy Role:

  • Long-term energy storage

  • Very energy-rich (9 kcal/g)

• Other Notes:

  • Too much saturated fat → high cholesterol → heart risk

  • Unsaturated fats = healthier for heart

3. Proteins Monomer, main function, food source, energy role, extra

• Monomers: Amino acids (20 types, 9 essential)

• Main Function:

  • Build and repair body tissues

  • Enzymes (speed up reactions)

  • Transport (e.g. haemoglobin)

  • Hormones (e.g. insulin)

  • Immunity (antibodies)

• Food Sources:

  • Meat, fish, eggs

  • Legumes, beans, soy, mycoprotein

• Energy Role:

  • Not main source of energy

  • Used only if carbs/fats are low

  • 4 kcal/g

• Other Notes:

  • Animal proteins = complete

  • Plant proteins = may lack some essential amino acids

  • Deficiency diseases: marasmus, kwashiorkor

4. Nucleic Acids (DNA & RNA)

• Monomers: Nucleotides (sugar + phosphate + nitrogen base)

• Main Function:

  • Store and transmit genetic information

  • DNA: Blueprint for making proteins

  • RNA: Helps build proteins

  • ATP (a nucleotide): Main energy carrier in cells

• Food Sources:

  • Found in all living cells (e.g. from meat, plants, anything with DNA)

• Energy Role:

  • Not used as energy source

  • But ATP stores energy for cellular use

• Other Notes:

  • Not broken down for fuel like carbs or fats

Metabolism

The sum of all the chemical reactions in living organisms.

Hydrolysis

Large organic molecules are broken down to smaller ones by the addition of water.

Condensation

Large molecules are built up from smaller ones by the removal of water.

Water

The most important biological solvent.

Diet

A total of the molecules or nutrients that we need.

Balanced diet vs Malnutrition

• A balanced diet provides all nutrients in the correct amounts, including carbohydrates, lipids, proteins, vitamins, minerals, water, and dietary fiber.

• Malnutrition occurs if the diet lacks nutrients in correct proportions.

Nutrition

Nutrition is the taking in of nutrients (organic substances and mineral ions), then absorbing and assimilating them.

Alimentary canal

• Specialized tube running from mouth to anus (also called gut).

  • Mouth: Mechanical digestion (chewing) and chemical digestion (salivary amylase).

  • Oesophagus: Muscular tube that moves food to the stomach by peristalsis.

  • Stomach: Stores food, mixes food with acidic digestive juices (hydrochloric acid and pepsin).

  • Small Intestine (Duodenum, Ileum):

    • Duodenum: Mixes food with pancreatic juice (amylase, trypsin, lipase) and bile.

    • Ileum: Absorption of digested food molecules.

  • Liver: Produces bile, important in assimilation.

  • Gall bladder: Stores bile.

  • Pancreas: Produces pancreatic juice.

  • Large Intestine (Colon, Rectum):

    • Colon: Reabsorbs water from gut contents.

    • Rectum: Stores faeces before expulsion.

  • Anus: Exit for faeces.

Ingestion

Taking food and drink into the body through the mouth.

Mechanical Digestion

Breaking food into smaller pieces without a chemical change to the food molecules.

Chemical Digestion

Enzymes break down large, insoluble molecules in the food to small, water-soluble molecules.

Absorption

Small digested food molecules and ions cross the wall of the intestine into the bloodstream or lymph.

Assimilation

Digested food is moved into the cells of the body, where they become part of the cells and are used for energy, growth, and repair.

Egestion

Dietary fiber and other indigestible substances pass out through the anus.

Oesophagus

a muscular tube which helps food move to the stomach by peristalsis.

Liver

produces bile, which helps to neutralise acidic chyme and also emulsifies fats. Important in assimilation.

Duodenum

first part of the small intestine, where semi-liquid food is mixed with pancreatic juice and bile.

Bolus

ball of food

Mastication

cutting and mixing food

Digestion

• Digestion converts large, insoluble molecules into smaller, soluble molecules via hydrolysis, catalyzed by enzymes.

  • Carbohydrate Digestion:

    • Salivary amylase (in mouth): starch→maltosestarch→maltose

    • Pancreatic amylase (in small intestine): starch→maltosestarch→maltose

    • Maltase (on small intestine wall): maltose→glucosemaltose→glucose

  • Protein Digestion:

    • Pepsin (in stomach): protein→amino acidsprotein→aminoacids

    • Trypsin (in small intestine): protein→amino acidsprotein→aminoacids

  • Fat Digestion:

    • Lipase (in small intestine): fats→fatty acids+glycerolfats→fattyacids+glycerol

    • Bile (from liver): Emulsifies fats to increase surface area for lipase.

Peristalsis

Waves of muscular contraction push the bolus down towards the stomach.

Salivary amylase

Enzyme that secreted in the mouth that catalyses the conversion of starch to maltose

Chyme

It is formed by the mixing of partially digested food with gastric juices. Chyme is then gradually released into the duodenum for further digestion and absorption. c

Water

Is absorbed from the gut contents that remain and indigestible food is then expelled.