human digestive systems

How do high temperatures cause enzyme activity to reduce

The energy from higher temperatures break the bonds that hold enzymes in its specific 3D shape, causing it do denature. The shape of their active site is less complementary to that of the substrate so there is reduced frequency of effective collisions so reduced rate of enzyme substrate complex formation hence enzymes activity reduces

State the chemical formula of simple sugars

C6H12O6

State the chemical formula of double sugars

C12H22O11

Why can enzymes be used multiple times?

Enzymes catalyse chemical reactions but remain CHEMICALLY unchanged at the end of the reaction so they can be reused repeatedly, unless denatured.

How do enzymes work better at their optimum temperature?

The enzyme’s active sites has a shape that is most complementary for binding with substrate, hence highest rate of enzyme-substrate complex formation and highest rate of reaction.

How do enzymes speed up chemical reaction?

Enzymes reduce the activation energy needed to start the reaction by providing an alternate pathway of lower activation energy.

State all the structural adaptions of the small intestines that help it absorb digested food at a faster rate.(3)

1. The inner wall of the small intestines has many finger-like projections that increase surface area to volume ratio for higher rate of absorption of digested food into the epithelial cells

2. The villi on the small intestine is one cell thick which allows a shorter distance for diffusion of digested food into food substances into cells.

3. Small intestine is long to increase time for absorption

What is the general chemical composition ratio of carbohydrates?

Number of Hydrogen:Number of oxygen =2:1 (eg.C6H12O6,C12H22O11)

What is the general chemical composition ratio for fats?

More hydrogen than oxygen (H>O)

What is the general chemical composition for proteins?

Have Nitrogen(N)

What is the test for starch and how to perform it?

Iodine test:

1. Add 2-3 drops of iodine solution to food sample

2. If starch is present, iodine solution turns from brown to blue-black.

   →If starch is not present, iodine solution remains brown.

What is the test for reducing sugars and how to perform it?

Benedict’s test:

1. Add 2cm³ of Benedict’s solution to 2cm³ of food sample (equal volume)

2. Shake the mixture

3. Heat a beaker of water until it boils

4. Leave the test tube in the boiling water bath for 2 minutes

5. If reducing sugars is present, Benedict’s solution turns from blue to green/yellow/brick red(as concentration of reducing sugars increases)

6. If reducing sugars are absent, Benedict’s solution remains blue.

What is the test for fats and how to perform it?

Ethanol emulsion test

1. Add 2cm³ of ethanol to food sample in a test tube and shake (if solid, cut and grind into small pieces before adding ethanol)

2. Clear solutions should be seen(since ethanol dissolves fats)

3. Add 2cm³ of distilled water into the test tube and shake the mixture

4. If fats are present, a cloudy white emulsion is seen

5. If fats are absent, solution remains clear on adding water

What is the test for proteins and how to do it?

Biuret test:

1. Add 2cm³ of sodium hydroxide solution to 2cm³ of food sample in a test tube(if solid, cut and grind into small pieces) and shake

2. Add 1% Copper(II) sulfate solution drop by drop, shaking the mixture after each drop

3. If proteins are present, light blue solutions turns into a violet solution

4. If proteins are absent, light blue solutions turns into remains blue.

Maltose is made from?

Glucose and glucose

Sucrose is made from?

Glucose and fructose

Lactose is made from?

Glucose and galactose

Lipids are made from?

Glycerol and fatty acids

What’s the main role of carbohydrates?

Carbohydrates provide an immediate source of energy, form supporting structures(cell wall) and form nucleic acids(eg dna)

What’s the main role of fats?

Fats provide long term storage of energy, forms an insulating layer below skin to prevent heat loss and cushions and protects vital organs

What are the main roles of proteins?

Protein is used in the synthesis of new protoplasm for growth and repair of worn out cells.

Describe the function and occurrence of cellulose

Cellulose is the structural form of carbohydrates to provide cell walls with mechanical strength and support, to protect plant cells and is present in cell walls in plants.

Describe the function and occurrence of Starch

Starch is the storage form of carbohydrates in plants that is easily digested to glucose to provide energy when needed. Starch is found in storage organs of plants (eg potato tubers)

Describe the function and occurrence of Glycogen

Glycogen is the storage form of carbohydrates in animals and is easily digested to glucose to provide energy when needed. Glycogen is stored in liver and muscles of animals

What is a catalyst?

A catalyst is a substance that seed ups chemical reaction but remains chemically unchanged after the reaction.

Explain the mode of action of enzymes using lock and key hypothesis

The enzyme (lock) has a specific 3D shape which contains an active site that is complementary to that of the substrate(key), to form an enzyme substrate complex. Chemical reaction occurs through an alternative reaction pathway of lower activation energy. The enzyme-substrate complex is converted into the enzyme-product complex. The product then detaches from the enzyme’s active site. The enzyme remains chemically unchanged at the end of the reaction and is able to bind to another substrate

How does optimum pH affect the rate of enzyme-catalyse reactions?(change the describing words to talk about lower pH/ higher pH)

At optimum pH, active site is most complementary to that of the substrate, highest frequency of effective collisions between enzyme and substrate, highest frequency of enzyme-substrate complex formation, hence highest rate of reaction

Function of mouth?(3)

1. Chewing action of teeth breaks down food into smaller pieces to increase surface area to volume ratio for more effective chemical digestion.

2. Salivary glands produce salivary amylase which catalyses breakdown of starch into maltose

3. Tongue rolls food into a bolus

Main function of oesophagus?(2)

1. Transports food to stomach via peristalsis

2. Mixes food with saliva digestive juices

Main functions of stomach?(3)

1. Stomach churns food via peristalsis

2. Secrets hydrochloric acid to kill bacteria and provide optimum acidic environment for gastric protease to work and catalyse the breakdown of protein into polypeptides

3. The resultant partially digested, semi-liquid food is called chyme

Pancreas function?(2)

1. Secrets pancreatic juice to digest food in the small intestine

2. Pancreatic juice is alkaline to neutralise acidic chyme to provide optimum pH for pancreatic amylase, pancreatic protease and pancreatic lipase and intestinal enzymes to work.

Function of liver, gall bladder and bile duct(2)

1. The liver produces bile, which is stored in the gallbladder and is released into the small intestines via the built duct.

2. The bile emulsifies fats, breaking up large fat globules into smaller droplets to increase surface area to volume ratio for more efficient lipase-catalysed reaction.

Function of small intestine?(2)

1. Small intestine secrets intestinal juice to digest food, which is alkaline to neutralise acidic chyme, contains intestinal maltase, intestinal sucrose, intestinal lactase, erepsin, and intestinal lipase.(S.M.E.L.L.)

2. Absorbs water, mineral salts and vitamins

define peristalsis

peristalsis is the alternating contractions and relaxations of muscular walls