B3: Organisation & the Digestive System

What are the 7 food/nutrition groups?

Carbohydrates, lipids/fats, protein, vitamins, sugars, water, fibre, minerals

Sub units of complex carbohydrates?

simple sugars

Function of simple sugars

Releases energy via respiration, building blocks of complex carbohydrates

Function of complex carbohydrates

Energy store (glycogen + starch), structural support for plant cell walls (cellulose)

Subunits of lipids

fatty acids, glycerol

Function of lipids

long-term energy store, part of cell membrane, keeps you warm - thermal insulation

Protein subunits

amino acids

Function of proteins

provides structure (bone ligaments, cartilage, tendons, muscles), makes enzymes, hormones, antibodies

Test for starch + positive result

Place a small sample of the test solution on a spotting tile and add a drop of iodine solution. Orange --> black

Test for protein + positive result

Add Biuret reagent to the test solution in a test tube/spotting tile. Pale blue --> purple (depends on depth of colour)

Test for lipids + positive result

Place test solution in a test tube, add ethanol, then water and shake. clear --> cloud/white (near top - emulsifies)

Test for sugar

Place test solution in a test tube, add Benedict's reagent, and heat by standing the test tube in a beaker of hot water (80C).

Positive result for sugar

Blue --> green (little reducing sugars). --> orange - some reducing sugars. --> red - lots of reducing sugars

What is a catalyst?

A substance that speeds up the rate of a chemical reaction but it's not itself changed by the reaction

Where do enzymes occur (as biological catalysts)?

Occurs inside cells or secreted by cells

What is catalase?

The enzyme that catalysts break down by hydrogen peroxide

What is metabolism?

The sum of all of the reactions in a cell or body

What is the anabolic reaction that enzymes can speed up?

Anabolic reactions is the building of larger molecules from lots of smaller ones.

Give an example of an anabolic reaction

Starch from glucose

What is a catabolic reaction that enzymes can speed up?

It is the breaking down of larger molecules into smaller ones

Describe the third reaction that enzymes can speed up + e.g.

The changing of one molecule into another - glucose -> fructose using isomease

Give an example of a catabolic reaction

Breaking down proteins into amino acids

Give the steps of the lock and key model/enzymes working

1. A solution of the enzyme is mixed with a solution containing substrate molecules

2. 1 substrate molecule fits neatly into the active site of the enzyme, like a lock and key

3. Some bonds in the substrate molecule break --> formation of 2 product molecules

4. Product molecules are a different shape to the substrate so no longer fit into the active site + released

5. Active site of the enzyme molecule is free to accept another substrate molecule

Describe denatured enzymes

Enzymes where the active site has changed shape and the substrate will no longer fit; it cannot go back to normal

Describe an enzyme and rate of reaction graph: Before optimum temp

Molecules gain kinetic energy, the speed they move increase and the frequency of collisions between enzymes and substrate increase.

Describe an enzyme and rate of reaction graph: After optimum temp

Enzymes are denaturing, the active site changes shape, there are fewer/no enzyme substrate complexes form

Describe a pH and rate of reaction graph

It is a bell shaped graph; if the pH is too high/low, the enzyme denatures and the active site no longer fits the substrate

Name tissues + organs in digestive system (in order ish)

mouth, salivary glands, oesophagus, stomach (liver, gall bladder), pancreas, small intestine, large intestine, rectum, anus

What enzyme breaks down carbohydrates to glucose

Carbohydrase/amylase

Where is carbohydrase/amylase produced

Salivary glands, pancreas, small intestine

Where is amylase used?

mouth, small intestine

What does protease break down?

protein to amino acids

Where is the protease enzyme produced

stomach, pancreas, small intestine

Where is protease used in the digestion system

stomach, small intestine

What does lipase break down?

lipids (fats) to fatty acids and glycerol

where is lipase produced

pancreas, small intestine

Where is lipase used in the digestion system

small intestine

Why is the pH in the stomach acidic

contains HCl, helps kill any bacteria in the food, enzymes produced in stomach work best in acidic conditions

What does bile do?

used to neutralise the stomach acid and provides alkaline conditions for lipase in small intestine, emulsifies lipids thus increasing surface area (in s. i.)

Function: mouth

Mechanical digestion - teeth and tongue - increases surface area, chemical digestion - amylase

Glandular/muscular tissue present - mouth?

Salivary glands, muscle (tongue)

Glandular/muscular tissue present - oesophagus/gullet?

muscular

Function: stomach

Mechanical digestion - muscle contractions punching food, chemical digestion - HCl - kills bacteria

Glandular/muscular tissue present - stomach

muscular and glandular

Function: liver

Produces bile

Function: gall bladder

stores bile

Function: pancreas

produces enzymes

Function: large intestine

Peristalsis - mechanical digestion - squeezes food