Biological molecules pt1

Question 1

Define metabolism

Answer 1

The sum total of all biochemical reactions taking place in an organism

Question 2

What are anabolic reactions?

Answer 2

Building smaller molecules into larger ones. Often involves condensation and forms polymers

Question 3

What are catabolic reactions?

Answer 3

Involves breaking down large molecules into small ones. Often involves hydrolysis

Question 4

Condensation

Answer 4

Two molecules are joined together when a covalent bond is formed by the elimination of water.

Question 5

Hydrolysis

Answer 5

A molecule is broken down when a covalent bond is broken by the addition of water.

Question 6

Anion

Answer 6

Negatively charged ion

Question 7

Cations

Answer 7

Positively charged ion

Question 8

Carbohydrates main functions

Answer 8

Energy source e.g glucose
Energy store e.g starch
Structure e.g cellulose

Question 9

3 main types of carbohydrates

Answer 9

Monosaccharides (single, simple molecules)
Disaccharides (molecules made by joining two single sugars together)
Polysaccharides (polymers made by joining many single sugars together)

Question 10

Monosaccharides are…

Answer 10

Soluble in water
Sweet tasting
Crystalline

Question 11

Glucose

Answer 11

C6H12O6
alpha glucose and beta glucose
two alpha glucose joined to make maltose
hundreds of alpha glucose joined to make glycogen and starch
Hundreds of beta glucose molecules joined to make cellulose
ABBA- alpha below and beta above

Question 12

Draw alpha and beta glucose

Answer 12

See notes.

Question 13

Disaccharides

Answer 13

Two alpha glucose joined by condensation to make maltose
maltose= disaccharide
The covalent bond formed by condensation is a 1,4 glycosidic bond

Question 14

Tests for sugars (reducing sugars)

Answer 14

all monosaccharides and many disaccharides are reducing sugars
Reducing sugar is heated with Benedict’s solution (pale blue solution of alkaline copper II sulphate)
Sugar is reduces copper sulphate to form a Brick Red precipitate.
Goes to green- orange-brick red

Question 15

Tests for sugars (non-reducing sugars)

Answer 15

Do the Benedict’s test for reducing sugar to make sure the result is negative and the solution stays pale blue.
Then boil the non reducing sugar with hydrochloric acid (hydrolyses molecule)
Cool the sample and neutralise with sodium hydrogen carbonate- breaks glycosidic bond
Do the Benedict’s test on the hydrolysed sample- a brick red precipitate will form.

Question 16

Quantitative test for glucose

Answer 16

Benedict’s test is qualitative- tells if reducing sugar is present or not
Test can be made quantitative to find out how much reducing sugar is present

Question 17

How does the quantitative test work

Answer 17

More reducing sugar= more copper sulfate used up in a reaction= paler Benedict’s solution= paleness can be measured using a colorimeter

Question 18

How the colorimeter works

Answer 18

Light is shone through sample
Sample is placed a cuvette
cell measures how much light gets through sample
The % of light which gets through the sample is recorded as percentage transmission

Question 19

How to do the quantitative test

Answer 19

Make up a range of glucose solutions of known concentrations
Do Benedict’s test on the standards
Filter off the precipitates and measure % transmission using colorimeter
Plot a calibration curve of % transmission against glucose concentration
Do Benedicta test n samples, filter and measure % transmission
Use the calibration curve convert transmission readings of samples to glucose concentrations

Question 20

Starch

Answer 20

An energy store in plants
Mixture of two polysaccharides called amylose and amylopectin
Long chain of hundreds of alpha glucose joined together by 1,4 glycosidic bonds
Insoluble- does not affect water potential
chains of amylose coil into a compact helix shape

Question 21

Test for starch

Answer 21

Iodine solution added to starch
Positive- blue-black
Negative- yellow-brown

Question 22

Glycogen

Answer 22

an energy store in animals
Glycogen a polysaccharide polymer of alpha glucose joined by 1,4 glycosidic bond
Glycogen is branched making it compact
branches made by 1,6 glycosidic bonds between alpha glucose molecules

Question 23

Why are starch and glycogen ideal energy stores?

Answer 23

Compact- a lot stored in a small space
insoluble- Doesn’t affect water potential, no osmotic effect
Unreactive- stable stores of glucose
Easily hydrolysed by enzymes- release glucose quickly when needed

Question 24

Cellulose

Answer 24

Structural polysaccharide in a plant cell walls
Thousands of beta glucose joined by 1,4 glycosidic bonds formed through condensation
Every second beta glucose rotated 180 degrees
Straight and unbranched- cellulose molecules line up close together forming bundles called microfibrils
microfibrils held together by H bonds to form larger bundles called macrofibrils
Insoluble and very strong

Question 25

Water

Answer 25

Two H atoms covalently bonded to one O atom
Electrons in these bonds are not shared evenly
O atoms are slightly negative and the H atoms are slightly positive
Held together by hydrogen bonds
An excellent solvent
Its polarity causes it to interact with other polar or charged substances
water molecules cluster around ionic substances and polar molecules and pull the individual ions and molecules apart

Question 26

Roles of water

Answer 26

Transport medium- good solvent, H bonds make water a liquid at a wide range of temperatures, water can flow as a body carrying dissolved substances
Ice and insulation- Has a lattice structure , ice is less dense than water, floating ice insulates the water below it
Cohesion- H bonds are cohesive and helps to draw water up the xylem during transpiration, also creates surface tension
Environment- large specific heat capacity- large amount of energy needed to raise the temperature, oceans have fairly constant temperatures and provide a stable thermal environment
Reactant- used in hydrolysis reactions
Coolant- high latent heat of evaporation, when water evaporates it draws heat energy from its surroundings