Biology AS AQA Enzymes and the Digestive System

Made these notes for my year 12 summer exam to revise and read over. There are spelling mistakes in most of my files but due to the busy exam schedule I had no time to correct them (sorry).

Most files have more information than what is needed but I feel it helps you feel more confident walking into the exam if you have a greater knowledge background and may help when having to apply knowledge to questions. Good luck :)

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  • Created by: Chelcie
  • Created on: 02-09-13 12:35

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Enzymes and the Digestive System
PHYSICAL BREAKDOWN
Broken down to smaller pieces e.g. teeth
Provides large surface area for chemical digestion

CHEMICAL DIGESTION
All digestive enzymes function by hydrolysis: Splitting up of molecules by adding water to the
chemical bonds.
ASSIMILATION: Where molecules are incorporated into body tissues and/or used…

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Test for reducing sugars ­ BENEDICT'S TEST

All monosaccharides and some disaccharides are reducing sugars.
Reduction is the chemical reaction involving the gain of electrons.
Reducing sugars can donate electrons to another chemical (Benedict's reagent)
Benedict's is an alkaline solution of copper sulfate.
When sugar is heated, Benedict's forms an…

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Test for proteins- BIURET TEST
Biuret test detects peptide links.
1. Add solution with sodium hydroxide solution
2. Add drops of very dilute copper sulfate solution
3. Goes from blue to purple




POLYSACCHARIDE DIGESTION- STARCH DIGESTION
Different enzymes work at different pHs (so different enzymes at different parts of body)…

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Structure of an Amino Acid
Amino acids are the monomer which combines to make the polymer
polypeptide.
Polypeptides form to make proteins.
Contains amino group (-NH), carboxyl group (-COOH), hydrogen atom (-H), R
group.

Formation of a Peptide Bond
Amino acids combine to form dipeptide.
Condensation reaction with removal of…

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FIBROUS PROTEINS
Have structural functions.
E.g. collagen found in tendons (held together by cross-linkages of adjacent chain amino acids):
Primary- unbranched polypeptide chain
Secondary- tightly wound chain
Tertiary- Twisted into a second helix
Quaternary- 3 polypeptide chains

GLOBULAR PROTEINS
Carry out metabolic functions.
E.g. enzymes, haemoglobin.


Enzymes as Catalysts
CATALYST:…

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Induced fit model
Rather than the enzyme being rigid, the enzyme is flexible and changes its shape slightly to fit the
profile of the substrate.
As the enzyme changes its shape, it puts a strain on the substrate molecule which distorts
particular bonds lowering its activation energy enough to break…

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Effect of pH
The pH of a solution is a measure of its hydrogen ion concentration.
A change in pH alters the charges on the amino acids that make up the active site. As a result, the
substrate cannot form enzyme substrate complexes.
A change in pH can cause the…

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