Human DigestionHuman DigestionTopic 6.1 pg 67

What is digestion all about?What is digestion all about?

Ingestion – eating the food (the fun bit) Digestion – series of chem reactions where

food is reduced into smaller & smaller molecules

Absorption – nutrients pass through cells of digestive system into blood or lymphatic vessels

Transport – nutrients enter blood or lymphatic system & are transported around the body

Why is it important to digest Why is it important to digest large food molecules?large food molecules?

Need to be digested in order to be absorbed

To be absorbed molecules must be small enough to cross the cells (plasma membranes) lining the gut & eventually get into the bloodstream

Macromolecules from animals/veg /fruit etc (polymers) to monomers; we can then make human macromolecules

Campbell online act 41.1 pg 1

Why are enzymes required?Why are enzymes required?

Speed up breakdown (hydrolysis) of macromolecules by lowering activation energy

Temperature cant be used to supply energy needed to activate reaction; enzymes allow reactions to occur at normal body temps

Each enzyme is specific for certain food type

Enzyme revisionEnzyme revision

How do enzymes act to lower the activation energy?

By holding the substrate in the activate site it puts stress on the bonds holding the substrate molecule together – when bonds are stressed it increases chance that surrounding thermal energy will be sufficient to break the bonds

Campbell online act Campbell online act 41.1 pg 3-541.1 pg 3-5

Amylases starch Proteases proteins Lipases lipids Nucleases nucleic acids

Enzyme examplesEnzyme examples

Enzyme e.g. Salivary amylase Pepsin (Protease) Phospholipase A2

Source Saliva (salivary glands)

Gastric Juice (stomach cells)

Pancreatic Juice (chief cells)

Substrate starch proteins phospholipds

Product Maltose & glucose Amino acids Glycerol, fatty acids

pH 7 2-3 8

Human Digestive System – Human Digestive System – the alimentary canalthe alimentary canal

FunctionsFunctions

anus - the opening at the end of the digestive system from which feces exit the body.

esophagus - the long tube between the mouth and the stomach. It uses rhythmic muscle movements (called peristalsis) to force food from the throat into the stomach.

gall bladder - a small, sac-like organ located by the duodenum. It stores and releases bile (digestive chem produced in liver) into the small intestine.

FunctionsFunctions

large intestine - the long, wide tube that food goes through after it goes through the small intestine.

liver - a large organ located above and in front of the stomach. It filters toxins from the blood, and makes bile (which breaks down fats) and some blood proteins.

FunctionsFunctions

mouth - the first part of the digestive system, where food enters the body. Chewing and salivary enzymes in the mouth are the beginning of the digestive process (breaking down the food).

pancreas - enzyme-producing gland located below the stomach and above the intestines. Enzymes help in the digestion of carbohydrates, fats and proteins in the small intestine.

FunctionsFunctions

small intestine - the long, thin winding tube that food goes through after it leaves the stomach. Main function: chem digestion of carbs, lipids, proteins & absorption.

stomach - a sack-like, muscular organ that is attached to the esophagus; food is mixed with acids & enzymes chemical digestion. Food remains for few hours; peristalsis mixes food until almost fluid – called chyme; pyloric sphincter opens allowing small amounts of acid chyme into duodenum; repeated until stomach empty.

Main function: storage; chem digestion of proteins

After food is digested what After food is digested what happens?happens?

Nutrients (monomers) are absorbed & then assimilated

Absorption is the uptake of monomers across the plasma membranes of cells

Assimilation is when the nutrients are converted into protoplasm eg solid or fluid parts of cells/body

How do our bodies maximize How do our bodies maximize the absorption of nutrients?the absorption of nutrients?

Increasing the surface area over which absorption of nutrients can occur is key

Small Intestine is where majority of absorption occurs

Villi/microvilli cover the sml intestine lining