Human Nutrition Flashcards
Nutrition definition
The process by which organisms obtain and use food
Autotroph
Make their own food by photosynthesis
Eg: plants
Heterotroph
Can’t make own food, eat other plants or animals
Eg: humans
Herbivores
Eat plant material only
Eg: rabbit
Carnivores
Eat other animals
Eg: foxes, lions
Omnivores
Eat both plants and animals
Eg: humans and badgers
Functions of food
Make new cells
Replace old cells
Repair cells
Defend ourselves
Help in reproduction
Digestion
Is the chemical and physical breakdown of food into soluble form, it’s necessary for transport and absorption of digested food
Stages in human digestion
Ingestion
Digestion
Absorption
Assimilation
Egestion
- Ingestion
Taking in of food into the mouth
- Digestion
The mechanical and chemical breakdown of food into soluble form
- Absorption
The passage of the products of digestion into the blood or lymph
- Assimilation
The cell uses food (eg:) protein is used for growth and repair of cells
- Egestion
Removal of the undigested and unabsorbed material from the body
The mouth - physical digestion
Physical digestion in mouth is carried out by the teeth
Human Dental formula
2( i2/2, c1/1, pm2/2, m3/3)
Incisors
Used for cutting and biting
Canines
For tearing
Premolars
Crushing and grinding
Molars
Crushing and grinding
How many teeth in adults?
32
The mouth - chemical digestion
Carried out by the enzyme amylase — produced by salivary glands
pH of mouth
7-8
Amylase optimum pH
7-8
Amylase digests..
Starch into maltose
The Oesophagus
Is made of involuntary muscle, regular contractions push food along the guy
This is called peristalsis
Peristalsis definition
The alternate contraction and relaxation of the muscles of the gut wall
What stimulates peristalsis
Fibre
Lack of fibre effect:
Constipation
The stomach definition
A muscular bag which food remains for 2-4 hours. The wall of the stomach has gastric glands which produce HCL, enzymes and mucous.
What do gastric glands produce
HCL
Mucus
Enzymes
pH of stomach
2
The stomach - physical digestion
Occurs when stomach churns the food
This turns food into a liquid called chyme
The stomach - chemical digestion
Occurs due to the presence of protease enzymes.
The inactive enzyme pepsinogen is activated by HCL in the stomach to form Pepsin.
Pepsin digests protein into peptides
HCL function
Kills bacteria and other micro organisms that may’ve been ingested with the food
Why is the stomach not digested by pepsin of hcl?
Because of the protective mucous lining
The small intestine
The Duodenum
C shaped structure
Digestion occurs here
The duodenum what happens
Digestion occurs here
Liver produces Bile (sodium hydrogen carbonate, which neutralises pH and emulsifies fats)
Pancreas produces amylase and lipase
The ileum
What happens here
Absorption of nutrients into blood
Adaptions of ileum
Millions of villi increased surface are for absorption of materials
Micro villi present
Large blood supply
Only one cell thick
Lácteas function
Absorbs fats, fats are transported in lymphatic system, enter blood stream at subclavian gland
End products of digestion
Starch + amylase > maltose (hepatic vein)
Lipids + lipase > glycerol and fatty acids (lacteal)
Pepsinogen > pepsin + protein > amino acids (hepatic vein)
Movement of materials by
Diffusion or passive transport
Amino acids and deamination
Are toxic to the body the liver breaks them down into urea this is called deanination and urea goes to kidney to make urine
Excess carbohydrates
Are converted to glycogen and stored in liver
Pancreas function
Produces hormone insulin and a range of digestive enzymes such as amylase and lipase
Bile function
Formed by breakdown of red blood cells
Composed of water bile salts and pigments
Made in liver stored in gall bladder
Used to emulsify fats and neutralise acid from stomach (sodium hydrogen carbonate)
Functions of liver
Breaks down poisons
Breaks down old red blood cells
Makes bile
Neutralises chyme
Large intestine function
Reabsorb water and make b and k vitamins
Symbiotic bacteria in large intestine
Vitamin B and K
Break down cellulose
