Human nutrition flashcards

Topic 8: Human nutrition

Balanced diet

A diet with all the nutrients in the correct proportions and enough energy for the person's needs (which vary with age, sex, activity and pregnancy).

Vitamin C and vitamin D: why needed, and deficiency diseases

Vitamin C: collagen for healthy gums, skin and blood vessels; lack causes scurvy. Vitamin D: absorbing calcium for bones and teeth; lack causes rickets.

Calcium and iron: why needed, and deficiency

Calcium: hard bones and teeth (also clotting, muscle contraction); lack can cause rickets. Iron: haemoglobin to carry oxygen; lack causes anaemia (tiredness, pale skin).

Physical vs chemical digestion

Physical: breakdown of food into smaller pieces without chemical change, increasing surface area for enzymes. Chemical: breakdown of large insoluble molecules into small soluble ones that can be absorbed.

Peristalsis

Waves of contraction of the longitudinal and circular muscles of the gut wall that move food through the digestive system.

Jobs of incisors, canines, premolars and molars

Incisors: biting and cutting. Canines: gripping and tearing. Premolars and molars: grinding and crushing.

Digestive enzymes: substrate → products

Amylase: starch → maltose. Maltase: maltose → glucose. Protease (pepsin, trypsin): protein → amino acids. Lipase: lipids → fatty acids and glycerol.

Bile: where made, where stored, and what it does

Made in the liver, stored in the gall bladder. It emulsifies fats into small droplets, increasing the surface area for lipase. This is physical: bile contains no enzyme.

Function of hydrochloric acid in the stomach

It kills ingested bacteria. (The stomach is acidic and pepsin works best at that pH.)

Absorption vs assimilation

Absorption: movement of nutrients from the intestines into the cells lining the gut and then into the blood. Assimilation: uptake and use by cells of nutrients from the blood.

Features of a villus that help absorption

Villi and microvilli give a large surface area; epithelium one cell thick gives a short diffusion distance; capillaries absorb glucose and amino acids; the lacteal absorbs fatty acids and glycerol.

Where is most water absorbed, and where do absorbed nutrients go?

Most water is absorbed in the small intestine (some in the colon). The hepatic portal vein carries absorbed molecules from the ileum to the liver.