Human nutrition Flashcards
A balanced diet
contains the correct amount and proportion of carbohydrates, proteins, fats, vitamins, minerals, water, fiber (roughage).
Principal and dietary sources are:
- carbohydrates
- fats and oils
- proteins
- vitamin C and D
- mineral ions
- iron
- fibre ( roughage)
- water
carbohydrates
Needed for: energy.
Sources: Potatoes, wheat(often made into bread or pasta), rice and maize.
fats and oils
Needed for: energy, to make cell membrane. Stored under skin in adipose tissue to reduce heat loss from body to air. Provide mechanical protections for organs like kidney by forming a layer around them. Sources: cooking oil, meat, dairy product and oily fish.
proteins
Needed for: to build new cells for growth, to make hemoglobin, insulin, and antibodies.
Sources: meat, fish, eggs, dairy products, peas, beans, nuts, and seeds.
Vitamin C:
Needed for: to make the stretchy protein collagen found in skin and other tissues. Help tissue in good repair.
Source: citrus fruit, such as oranges, lime and raw vegetables.
Vitamin D:
Needed for: helps calcium to be absorbed for making bones and teeth.
Sources: oily fish, liver, red meat, egg yolk, sun
Calcium:
Needed for: bones and teeth and blood clotting.
Source: Milk and other daily products, bread.
iron:
Needed for: making hemoglobin the red pigment in blood, which carries oxygen.
Source. liver, red meat, egg yolk, dark green vegetables.
fibre (roughage)
Needed for: Absorb and remove, toxins, prevent constipation.
Source: all plant food such as fruits and vegetables.
water
Needed for: An important solvent. Metabolic reaction can only take place in
a solution. Plasma is mostly water. Cytoplasm is mostly water. To dissolve
enzymes and nutrients in alimentary canal.
Source: By drinking fluid and some fruits.
Vitamin C deficiency causes scurvy
which causes pain in joints and muscles and
bleeding from gums and other places. This used to be a common disease for sailors who had no fresh vegetables during long voyages.
Vitamin D deficiency causes
rickets, in which the bones become soft and deformed;
this disease was common in young children in industrial areas, who rarely got out
into the sunshine.
Calcium deficiency results in
brittle bones and teeth; poor blood clotting.
Iron defficiency causes
anaemia, in which there are not enough red blood cells so the
tissues do not get enough oxygen delivered to them.
Ingestion
taking of substances, e.g. food and drink, into the body. Occurs in mouth.
digestion
the breakdown of food
absorption
the movement of nutrients from the intestines into the blood
assimilation
uptake and use of nutrients by cells
egestion
the removal of undigested food from the body as faeces.
Oesophagus
Food travels down the oesophagus into the stomach.
Stomach:
Contains strong muscular walls. Muscles relax and contract to mix food enzyme and mucus.
Goblet cells in the walls secret mucus.
Digest protein.
Produce hydrochloric acid. Hydrochloric acid lowers the pH to about 2, which is the optimum pH for protease in the stomach. After the Stomach, the food moves into the duodenum.
Small intestine:
Duodenum:
Mix food with bile and pancreatic juice.
Absorption of minerals, and other nutrients begins in the duodenum.
Ileum:
Absorb digested nutrients into blood.
Absorb water.
Large intestine:
Colon:
absorb remaining water
Rectum:
Store faeces.
Salivary gland secrete
saliva in mouth, which contains the enzyme amylase, that
starts the digestion of a starch.
Pancreas secretes
digestive juices, which helps in digestion of fat
Liver produces bile
It is stored in gallbladder. Bile increase the pH of acidic food
from the stomach. And emulsifies fat.
More water is absorbed in small intestine than
large intestine.
Physical digestion
breakdown of food into smaller pieces without chemical
change to the food molecules.
Physical digestion increases the
surface area of food for the action of enzymes in
chemical digestion.
The tooth is embedded in the
gum
Incisors
chisel shaped for biting off pieces of food.
Canines
very similar to incisors in humans.
Premolars
have wide surfaces for grinding food.
Molars, like premolars, are used for
grinding
Muscular walls of the stomach, mix the
food, enzyme and mucus together in the process of churning.
Chemical digestion
break down of large insoluble molecules into small soluble
molecules
The role of chemical digestion
producing small soluble molecules that can be
absorbed.
Amylase breaks down
starch to maltose. It is secreted by salivary glands in mouth
and by pancreas in duodenum
Maltase breaks down
maltose to glucose. Maltase is secreted by the cells in the
lining of the small intestine on the membranes of the epithelium lining of the small intestine.
Pepsin breaks down
protein in acidic conditions and is secreted by the walls of the
stomach
Trypsin breaks down
rotein in alkaline conditions and is secreted by the pancreas
in the duodenum.
Lipase breaks down
fats and oils to fatty acids and glycerol. It is secreted by the
pancreas in the duodenum.
The function of hydrochloric acid in gastric juice is to
kill harmful microorganisms in food and provide an acidic pH for optimum enzyme activity
Bile
an alkaline mixture that neutralizes the acidic mixture of food and gastric juices entering the duodenum from the stomach, to provide a suitable pH for enzyme action
Small intestine is the
region where nutrients are absorbed.
Most water is absorbed from the small intestine but some is also absorbed from the
colon
Villi and microvilli increase the
internal surface area of the small intestine and help in
faster absorption of dissolved nutrients.
Villi
are tiny projections on the internal wall of the small intestine. The cell membrane on the surface of each villus is folded to form many tiny microvilli. Villi contains lacteal and blood capillaries.
Capillaries in villi
absorb glucose, amino acids, fatty acids, glycerol, vitamins, mineral ions and water. These blood capillaries join to form hepatic portal vein, which takes all of these substances to the liver.
The fatty acids and glycerol pass
into the lacteals. The contents of the lacteals are eventually emptids into the blood.
