Biology- Enzymes + Food (Year 9 Spring Term Test)

enzyme

a biological catalyst that increases the rate of reaction in living organisms

Active site

specific region of an enzyme where the substrate binds and the reaction takes place

2 types of chemical reaction

Breakdown 00 -> 0 + 0 Synthesis 0 + 0 -> 00

Lock and Key Model

1. Substrate collides with active site of enzyme -> enzyme - substrate complex

2. Enzyme catalyses breakdown of substrate -> enzyme - product complex

3. Products released from active site

Substrate and active site have to be…

Complementary in shape

Protein: Enzyme, where, smaller molecules

Enzyme: Protease

Where: Stomach+ small intestine

Smaller molecules: amino acids

Starch: Enzyme, where, smaller molecules

Enzyme: amylase

where: mouth+ small intestine

smaller molecules: sugars (glucose)

Lipids: Enzyme, where, smaller molecules

enzyme: lipase

where: small intestine

smaller molecules: fatty acids + glycerol

Denaturing enzymes

if enzymes are exposed to extremes of pH or temperature the shape of their active site may change and the substrate will no longer be able to fit in.

Effect of TEMPERATURE of Enzyme Activity

-Enzyme activity is HIGHEST at Optimum Temperature -below optimum temp there are fewer collisions (activity decreases) -above optimum temp the enzyme denatures (activity decreases)

Effect of pH on Enzyme activity

-Highest at optimum pH, this depends on where the enzyme is found in the body -Below or Above optimum pH the enzyme denatures (activity decreases)

Effect of SUBSTRATE CONCENTRATION on Enzyme activity

• As substrate concentration increases so does rate of reaction -low concen= limiting factor: (active sites are empty) -medium: more substrates than enzymes -high: limiting factor = enzyme concentration(active sites are full)

CORE PRACTICAL: Investigating the effect of pH on amylase VARIABLES

Independent: pH buffer solution value (ph3,5,7,9) Dependent: time taken Control: temp, volume of solutions

CORE PRACTICAL: Investigating the effect of pH on amylase METHOD

-place iodine into spotting tile

• put test tubes containing amylase+pH buffer and starch solution in a water bath at 40°C. -pour starch solution into amylase+pH buffer and start stopwatch -every 20 seconds add a drop of mixture to the iodine until it remains yellow

• repeat for other pH buffers

CORE PRACTICAL: Investigating the effect of pH on amylase RESULT

Amylase breaks down starch into glucose. At pH 7 this took the shortest time for the iodine to remain yellow. This shows starch is broken down quickest at this pH. This is because amylase is found in the mouth where the pH is 7.

Rate of reaction

1/ seconds

Test for STARCH

-add iodine to test solution Positive Result: turns BLACK

Test for PROTEIN

-add Biuret solution Positive Result : turns PURPLE

Test for REDUCING SUGAR

-add Benedict's solution and black in water bath at 80°C Positive Result: turns RED

Test for Lipids

-add ethanol to solution and pour into a test tube of eater Positive Result: WHITE EMULSION

Calorimeter

measures the energy in our food

Calorimetry method (simple)

-as food burns water in the test tube is heated up -the change in temp of the water can calculate the ENERGY CONTENT