B2 Exam Revision

Plant cells vs. Animal cellsBoth types of cell have these: Only plant cells

have these:

Nucleus

This controls

the cell Cytoplasm This is the jelly like substance where chemical reaction take place

Cell wallGives support to the cell

Large vacuoleLarge space filled with cell sap Cell

membraneControls what goes in and out of the cell

1)

2)

3)

6)

5)

7)

Mitochondria Energy is released here by respiration

4)

ChloroplastsWhere photosynthesis takes place

Complete this definition of Diffusion using the key words:

Diffusion is the _______ __________ of ______ from where there are lots of particles ( high __________) to where there are less particles.

We say the particles diffuse down a concentration _________.

In cells, the cell membrane has small holes that allow small particles through, but not large molecules. We call this membrane ________ ________.

The bigger the difference in concentration, the faster the rate of ________.

Partially permeableDiffusionConcentration

GradientRandom movementParticles

Photosynthesis - The equation

1. What factors are needed to make glucose?2. What products are made by photosynthesis?

Limiting factors

• If you alter the levels of light, carbon dioxide or change the temperature the rate of photosynthesis will change!

What happens to the glucose?

Food chainsA food chain shows where the energy goes in a food chain

(in other words, “what gets eaten by what”):

Cabbage

Rabbit Stoat Fox

The arrows indicate where the energy is going

Plants convert the sun’s energy into

food

Pyramids of biomassIn this food chain we can see that the mass of organisms in each stage is less than in the previous stage:

Cabbage

Rabbit Stoat Fox

We can draw a “Pyramid of Biomass” to show this pattern:

Mass of cabbages

Mass of rabbits

Mass of stoats

Mass of foxes

Enzymes

• Enzymes are biological catalysts, they increase the rate of reactions.

• Enzymes are protein molecules made up of long chains of amino acids.

• When enzymes are denatured the active site changes shape.

What happens at the active site?

In the same way that a key fits into a lock, so a substrate is thought to fit into an enzyme’s active site. The enzyme is the lock, and the reactant is the key.

+ ↔ ↔ +

enzyme

reactant

+enzyme-reactant

complex↔products

enzyme

+↔

Factors affecting enzymesIf the temperature and pH changes sufficiently beyond an enzyme’s optimum, the shape of the enzyme irreversibly changes.

normal denatured

heat

pH

This affects the shape of the active site and means that the enzyme will no longer work.

When this happens the enzyme is denatured.

Aerobic Respiration

Oxygen + Glucose Carbon Dioxide + Water

Energy

+ +

Amylase

Protease

Lipase

Bile

Hydrochloric acid

Where are the enzymes found?

Enzymes of digestion

Chromosomes, Genes and Alleles

1. …………..

2. ……….......3. ……………..

4. ………………

Bb

5. …………….

Nucleus, Gene, Chromosome, Allele, Cell

(b)

Why was his work not spread quickly?

• He was not a famous scientist – nobody knew about him at the time.

• His job as abbot stopped him giving lectures at universities.

• He published his work in an obscure journal that few people read.

• Biologists at the time did not think mathematics had anything to do with Biology.

Gregor Mendel (The Pea Plant Man)

Disease

• Some disorders are inherited

• Huntington’s disease is caused by a dominant allele of a gene and can be inherited from only one parent

• Cystic fibrosis is caused by a recessive allele of a gene and so must be inherited from both parents

Cystic Fibrosis• The treatment involves

chest physiotherapy.• They are very prone to

chest infections and malnutrition.

• The mucus encourages the growth of pathogenic microbes that cause infection and cause long term lung damage.