Curiosity Is A Door To New Dicoveries

Wednesday, May 5, 2010

Why do people living at higher altitudes have rosy cheeks?

They need more red blood cells so that it will be more efficient to transport oxygen as the air high up is very thin.

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Doubts? What are the differences?

Polypeptides/peptones- shorter chains of amino acids(when proteins are not completely digested)

Pepsin- work well at pH 2 (protease)

Trypsin-work well at pH 9 (protease)

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Digestive system in a fish?

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Do parasitic worms like tapeworms, have a transport system?

NO!! They simply absorb digested nutrients from their surroundings by diffusion. The short distance between the surroundings and the cell means a transport system is not needed.

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Why is it that hydrochloric acid is produced, of pH 1 and 2.5,yet the stomach wall can withstand the corrosive effect of the acid?

Normally, the stomach cells produce a thick layer of mucus, preventing the acid from coming into direct contact with the cells.

Also, the gastric secretions containing the acid are produced only when food is present.

In any case, the stomach lining is replaced every three days by the constant production of the new mucosal cells by cell division.

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Sunday, May 2, 2010

Factors which affect the enzyme's activity?

1. pH

2. Temperature

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Enzymes

biological catalysts
speeds up or alter the rate of chemical reactions without themselves being chemically changed at the end of the reaction
is reusable, can be used again to catalyse reaction with the specific substrate molecule
small amount of enzyme needed to catalyse a relatively large amount of reaction
substances on which enzymes work on are called substrates
soluble in water
specific in action
has active site which will fit a particular substrate

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How is the small intestine adapted to its function?

blood capillaries- transport glucose + amino acids
epithelial- some secretes mucus
Lacteal- transport fats +glycerol
many finger-like parts, villi, to increase surface area for quick absorption of digested food
each villus is closely connected to a network of blood capillaries which send the digested food substance away quickly forming a diffusion gradient.

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Parts of the digestive system

Buccal cavity

the teeth grind the food into smaller substances, so as to increase the surface area for salivary amylase to work on.
Te tongue will then roll the food into a bolus so that it can travel down the oesophagus more easily.
Starch is broken down into maltose.

Oesophagus

peristalsis will occur
series of wave-like contractions of muscular walls-circular and longitudinal muscles
improved by exercising regularly
constipation can be prevented when peristalsis is consistent and roughage or fibre is consumed.

Stomach

muscular, elastic bag,with thick, well-developed stomach wall
pH 2
churns food into liquid chyle
secretes pepsin and hydrochloric acid
pepsin is a protease that works well in pH 2-acidic condition
hydrochloric acid- provides acidic condition for pepsin to work well/kills foreign particles,like germs and bacteria
protein is broken down into polypeptides/peptones(shorter chains of proteins) then into amino acids

Duodenum

all classes of food is digested- carbohydrates, fats, proteins
pancreas produce pancreatic juice containing enzymes(maltase,lipase,pancreatic amylase,trypsin), and sends it to the small intestine via the pancreatic duct
Emulsification: breaking down of fats into tiny fatty droplets, to increase surface area for lipase to work on, with the help of the bile
fats are digested into fatty acids and glycerol by lipase
proteins are digested by trypsin into amino acids
starch is digested into maltose by the pancreatic amylase
maltose is digested by maltase into glucose

Jejunum

chemical digestion is completed and absorption begins

Ileum

controlling flow of chyme into the large intestine

Large intestine

reabsorbs water and mineral salts from the undigested material/faeces
transport faeces to the rectum

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What is DIGESTION?

Digestion is the breakdown of complex food substances into smaller, soluble, simpler, diffusible substances as only small substances can pass through the pores of the partially-permeable membrane and be absorbed into the cell.

-Series of hydrolytic reactions catalysed by digestive enzymes.

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