1.4 Enzymes and Digestion

Economical benefit of enzymes in industry

Enzymes can speed up the rates of reaction without being used up, they lower the energy needed for reactions meaning reactions can take place at lower temperatures, overall enzymes make processes quicker and cheaper

Digestive system

The body system responsible for releasing small, soluble molecules from food that can be used by the body

Peristalsis

The involuntary constriction and relaxation of the muscles of the intestine, creating wave-like movements that push food contents along

Small intestine

The site of digestion completion where small soluble molecules are absorbed into the bloodstream

Ileum

The last portion of the small intestine, the walls of the ileum can produces enzymes such as amylase, protease and lipase to aid digestion

Enzymes

Biological catalysts that speed up reactions, they play an important role by breaking down large insoluble molecules into small soluble molecules that can be absorbed in the intestine

Amylase

Enzyme that breaks starch down into small, soluble sugars

Protease

Enzyme that breaks down proteins into small, soluble amino acids

Lipase

Enzyme that breaks down lipids into glycerol and fatty acids, which are small molecules that can be absorbed in the intestine

Specific adaptations of the ileum for digestion

Folded structure with a large surface area, also has villi which increase surface area for diffusion and are surrounded by blood vessels, permeable and thin, the rich blood supply maintains a steep diffusion gradient to optimise rates of diffusion and absorption

Villi

Small finger-like projections on the walls of the small intestine, increases surface area for absorption of soluble food molecules

Adaptations of the villi

Villi have an increased surface area and good blood supply, a single layer of epithelial cells, permeable, has a structure called a lacteal that can absorb fat products into the blood

Enzyme

Biological catalysts which speed up reactions without being used up

Enzymes and temperature

The enzyme rate increases as temperature increases up to an optimum, after which the enzyme becomes denatured

Enzymes and pH

The reaction rate decreases as the pH moves away from the enzyme's optimum pH

Denature

When the active site changes shape and can no longer bind to a substrate due to unsuitable temperature or pH

Active site

The part of an enzyme where the substrate binds

Substrate

Reactant of an enzyme catalysed reaction

Product

A substance produced in a chemical reaction

Lock and key theory

When a substrate fits into its enzyme just like a key fits a lock

Optimum rate

An ideal pH or temperature value that results in maximum enzyme activity

Amylase

A carbohydrase enzyme that breaks starch down into sugars

Starch

A large carbohydrate found in plants made up of many glucose molecules

Iodine solution

Turns from orange to blue-black in the presence of starch, will remain orange if starch has been broken down by amylase

Buffer solution

A solution that controls and keeps the pH of a solution to a specific range

Water bath

A container of water heated to a given temperature, the temperature can be adjusted for each test

Spotting tile

Equipment used to observe the colour changes of small quantities of reacting mixtures

Time taken for starch to break down

The dependent variable or factor that is measured in this experiment to investigate temperature and enzyme activity

Temperature of solutions

The independent variable or factor that is changed in this experiment to investigate temperature and enzyme activity, for example the first test could be carried out at 20 degrees Celsius and the second test could be at 30 degrees Celsius

Temperature ranges

A wide range of temperatures should be tested, the temperature intervals should be relatively small so the estimated optimum temperature value can be more accurate

pH

A variable that should be controlled in this experiment to ensure the results are valid, can be controlled with a buffer

End of reaction

The reaction can be confirmed as complete when iodine on the spotting tile no longer changes colour from orange to blue-black

Examples of other control variables

To ensure the results are valid the volumes and concentrations of all solutions should be controlled

Expected results

Amylase will break down starch effectively at an optimum temperature, this can be identified as the temperature condition that causes iodine to remain orange the quickest

Low temperatures and enzymes

Reduced chances of successful collision between enzymes and their complementary substrates

Effect of enzyme concentration

As enzyme concentration increases so will the rate of reaction, until saturation is reached

Denature

When the active site irreversibly changes shape and can no longer bind to a substrate due to high temperature or unsuitable pH

Amylase

A carbohydrase enzyme found in saliva and the small intestine that breaks the chemical bonds in starches

Protease

Enzyme found in the stomach and small intestine that breaks down proteins into amino acids

Lipase

Enzyme found in the small intestine that breaks down lipids into glycerol and fatty acids

Carbohydrases

Enzymes that speed up the breakdown of carbohydrates into simple sugars

Proteins

Building blocks of cells and tissues

Carbohydrates

Provide energy for chemical reactions

Lipids

Fats and oils which store energy

Inhibitors

Molecules that fit the active site of an enzyme but are not broken down, inhibitors reduce the rate of enzyme reactions

Digestion

A process that breaks down large insoluble molecules into smaller useful soluble molecules via enzymes, chemicals and mechanical action

Large insoluble molecules

Such as carbohydrates, proteins and lipids, need to be broken down during digestion into dissolvable products that can be absorbed by the body

Small soluble molecules

Products of digestion such as glucose, amino acids, glycerol and fatty acids, these molecules are small enough to be absorbed by the body for specific uses

Absorption

Small soluble molecules can be absorbed in the small intestine following digestion, they diffuse into the blood and are then transported around the body for specific purposes

Carbohydrates

Provide energy for chemical reactions and can break down into sugars

Proteins

The building blocks of cells and tissues that can break down into amino acids

Lipids

An energy store of fats and oils that can break down into glycerol and fatty acids

Conversion of glucose to complex carbohydrates

Glucose, a product of digestion, can be converted into new complex carbohydrates such as glycogen

Glucose

A soluble product of digestion, essential for respiration to release energy and is also needed to synthesise new molecules

Formation of lipid molecules

Glycerol and fatty acids, products of digestion, join together to form new lipids

Protein synthesis

Amino acids, products of digestion, join together in specific arrangements to form new proteins for growth and repair

Enzymes

Biological catalysts which speed up reactions without being used up, essential for the digestion of large insoluble molecules

Commercial and industrial use

Enzymes can be used to improve many products and industrial processes, they are used in detergents, making cheese, making alcohol and bread, making medicines and industrial chemicals

Biological detergents

Washing powders that contain enzymes such as protease and lipase and can save energy by working at lower temperatures

Economical benefit of enzymes in industry

Enzymes can speed up the rates of reaction without being used up, they lower the energy needed for reactions meaning reactions can take place at lower temperatures, overall enzymes make processes quicker and cheaper