B3 - Organisation and the Digestive System

What is a cell?

Basic building block of all living organisms.

What is a tissue?

group of cells with similar structure and function

What is an organ?

Group of tissues performing specific functions together

What is an organ system?

Organs working together to form an organism

Process in which cells become specialised

Differentiation

Types of tissue

1. Epithelial
2. Muscular
3. Glandular

Function of the digestive system

Break down large, insoluble molecules into small soluble ones.

Physical digestion

Involves physical movement such as chewing and muscle contraction to break down food into smaller pieces.

Chemical digestion

Involves chemical reactions using enzymes to break down the bonds that hold food molecules together.

Digestive system organs

1. Mouth
2. Oesophagus (peristalsis)
3. Stomach
* Liver
* Gall bladder
4. Small intestine
* Pancreas
5. Large intestine
6. Rectum
7. Anus

uses of proteins in the body

Creation of structural components, hormones, antibodies and enzymes

Structure of proteins

* Long chains of amino acids in different arrangements (animal proteins which we eat get broken down into amino acids and reordered into human proteins)
* Coiled into 3D shaped so other molecules can fit inside

Enzymatic reaction for protein

Protein + Protease \-----\> Amino acids

Uses for lipids in the body

* Energy source and secondary energy source
* Makes up structures in the cell membrane to help protect vital organs
* Natural insulator so keeps body heat in

Structure of lipids

* A glycerol head and 3 fatty acid stands attached to it
* Insoluble molecule

Enzymatic reaction for lipids

Lipid + Lipase \------\> Fatty acids + Glycerol

Uses of carbohydrates in the body

Main energy source

Structure of carbohydrates

* Carbon, hydrogen, oxygen
* Made up of one or more sugar monomers to form simple sugars or complex carbohydrates like starch and cellulose

Enzymatic reaction for Carbohydrates

Carbohydrate + Carbohydrase \------\> Simple sugars

Enzymatic reaction for Starch

Starch + amylase \--------\> Maltose + Maltase \--------\> Glucose

Food test for sugar

Benedict's solution + Heat from water bath

Positive: Brick red to green

Food test for starch

Iodine solution on a spotting tile

Positive: Blue-black

Food test for protein

Biurets solution

Positive: Lilac

Food test for lipids

Ethanol

Positive: White emulsion

Purpose of enzymes

Biological catalysts which speed up the rate of reaction by lowering the activation energy needed to start it.

Lock and key theory

Every enzyme has its own unique active site (lock) and only specific molecules/substrates can be complementary to it and fit like a key.

Enzyme substrate complex

A temporary complex formed when an enzyme binds to its substrate molecule(s).

Active site

The region on an enzyme that binds substance during a reaction.

Factors affecting enzyme activity

Temperature and pH

What happens if the temperature is too high or the pH too acidic or alkaline?

The enzyme will denature and its active site will change shape meaning that the substrate can no longer bind therefore the enzyme doesn't work.

Enzyme optimum

When the rate of an enzyme reaction is at its greatest value. Many enzymes have an optimum temperature of about 40 degrees Celsius and optimum pHs depending on where in the body they are found

What does optimum temperature do?

Increases the kinetic energy of the enzymes and the substrate so they move more and collide faster to join together which increases the rate of reaction.

Where is amylase made and where does it occur?

a) Mouth (salivary glands) + Small intestine + Pancreas

b) Salivary glands + small intestine

Where is protease made and where do it occur?

a) Stomach, small intestine, pancreas

b) Stomach, small intestine

Where is lipase made and where does it occur?

a) Small intestine, pancreas

b) Small intestine

How to calculate rate of enzyme reactions

Change/time

What are the 2 functions of bile?

1. Neutralise hydrochloric acid from the stomach to provide the optimum pH conditions for enzymes in the small intestine
2. Emulsify fats by breaking them down and increasing their surface area so lipase enzymes can work

Where is bile made?

Liver

Where is bile stored?

Gall bladder