IGCSE BIO 7. human nutrition

for assessment 2

balanced diet

contains :

* all seven required nutrients
* in correct amounts & proportions
* according to age / sex / level of activity

nutrients

molecules that provide energy

carbohydrate

* provides energy
* found in wheat, rice, bread, potatoes…
* deficiency : lack of growth / low body weight / fatigue

protein

* makes / repairs cell
* found in egg whites, meats, lentil, cottage cheese…
* deficiency : lack of growth / low body weight / fatigue

fat

* provides energy
* found in egg yolks, cheeses, avocado, vegetable oils, butter…
* deficiency : lack of growth, low body weight, fatigue

vitamin

any of a group of organic compounds which are essential for normal growth and nutrition and are required in small quantities in the diet because they cannot be synthesized by the body.

vitamin C

* used to make the collagen (type of protein) found in skin and other tissues, role in blood clotting
* water-soluble
* found in citrus fruits, spinach, guavas…
* deficiency : scurvy

scurvy

pain in joints and muscles, bleeding from gums and other tissues / loose teeth

vitamin D

* helps absorption of calcium, which makes bones and teeth
* fat -soluble
* can be overdosed
* deficiency : rickets (in children)

ricket

bones and soft and deformed / muscle cramps / stunted growth / reduced ability to absorb calcium

calcium

* needed to make bones and teeth, and for blood clotting
* found in cabbage, broccoli…
* deficiency : rickets

iron

* needed to make haemoglobin
* found in egg yolks, organ meats, red meats, spinach…
* deficiency : anaemia

haemoglobin

red pigment in red blood cells which transports oxygen to cells

anaemia

(an-haemia) not enough supply, so less oxygen supply to tissues, causing fatigue and brain fog

fibre

* adds bulk to food in the alimentary canal which stimulates peristalsis
* found in vegetables, fruits…
* deficiency : constipation

water

* found in vegetables, fruits…
* deficiency : dehydration

ingestion

taking of substances into the body

digestion

the breakdown of food

mechanical digestion

breakdown of food into smaller pieces without chemical changes to the food molecules

chemical digestion

breakdown of large, insoluble molecules into small, soluble molecules

absorption

movement of nutrients from the intestines through the intestinal wall, into the blood

assimilation

uptake of nutrients into the cells of the body where they are used, becoming part of the cells

egestion

removal of undigested food as faeces, through the anus

alimentary canal

the whole passage along which food passes through the body from mouth to anus during digestion

mouth

mechanical : chewing, saliva from salivary gland

chemical : amylase in saliva (starch → maltose)

ingestion / digestion

teeth

bite and grind food into smaller pieces, increasing the surface area for enzyme reaction

root

part of teeth embedded in the gum

crown

visible part of teeth above the gum, and it is covered with enamel

enamel

hardest substance made by body, and it can be corroded by acids produces by bacteria (cavity)

dentin

part having channels containing cytoplasm

pulp cavity

contains nerves and blood vessels, which supply the cytoplasm in the dentin

cement

anchors the teeth into the gum

nerve & blood supply

provide nutrients to the teeth and carry sensation from teeth to brain

incisor

chisel-shaped with a sharp edge

for cutting & bitting

canine

pointed

tearing flesh and fibres

premolar

2 cusps and 1-2 roots

chewing & grinding

molar

4-5 cusps and 2-3 roots

chewing & grinding

tongue

mixes food with saliva, forming bolus, which is shallowed

saliva

mixture of water, mucus and salivary amylase

* produced in salivary glands
* mucus
* amylase : digests starch to maltose

mucus

lubricates food so that it slides down the oesophagus easily

oesophagus

no digestion happening

peristalsis happens here

peristalsis

process of moving food bulk to stomach

stomach

mechanical : HCL

chemical : gastric juice - protein

gastric juice

pepsin : breaks down proteins to polypeptides

rennin : clots milt to enable the digestion of milk proteins by pepsin

hydrochloric acid

hydrochloric acid

* creates low pH required for pepsin
* denatures enzymes in harmful microorganisms in food
* destroys bacteria in food
* mechanical breakdown of proteins to polypeptides

small intestine

mechanical : bile

chemical : pancreatic juice, peptidases, lipase, lactase

absorption happens (water / nutrient)

long length which gives plenty of time to complete digestion / to absorb digested food as it slowly passes through

pancreatic juice

* from pancreas to duodenum
* contains :

→ pancreatic amylase : starch →

→ trypsin : work well in alkaline

→ lipase : lipid → fatty acid & glycerol

bile

* from gall bladder to duodenum
* greenish yellow
* alkaline → neutralize the acidic mixture from stomach
* emusify fats → increase the surface area for the chemical reaction
* pigment are made in liver with old haemoglobin
* later excreted through pancreas

lactase, peptidase, maltase in small intestine

* produced by the membranes of epithelium lining the small intestine
* they usually perform the later steps of digestion, breaking intermediate size molecules into small molecules

villus

tiny projection of inner wall into the intestinal lumen - large surface area for faster absorption

* single-cell walls - nutrients can quickly pass through the epithelium and reach capillaries and lacteals
* consists of : lacteal, capillaries, epithelium, microvilli

lacteal

linked with lymph vessel, where too big molecules such as fatty acids go

leads to liver, to detox

capillaries

surrounds lacteal, where soluble molecules such as glucose and amino acids go

leads to liver, to detox

epithelium

outermost layer of villus, which have epithelial cells with microvilli

microvilli

brush bordered epithelial cell lining on each villi

epithelial cell

covers the villi, and secrete enzymes (maltase, sucrase, lactase, peptidase, lipase) which does not enter the lumen of small intestine but stay close to epithelial cells

duodenum

starting part of small intestine, receives pancreatic juice from pancreas and bile from gall bladder, so most of digestion happens here

ileum

closest to the colon (large intestine) end, and it works to finish the job

large intestine

no digestion happens

absorption happens

consists of colon, rectum, anus

colon

biggest middle part of large intestine, where water is absorbed from the remaining material

rectum

right before anus, where the remaining, unabsorbed material (faeces) and dead cells from the lining of the alimentary canal and bacteria, are compacted and stored

anus

faeces are egested through a sphincter