Biology, GCSE (B7)

Exam: 12th June

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All living things are made up of Cells
A group of Cells e.g. Heart Muscle makes up a Tissue e.g. Heart Muscle Tissue
A group of Tissues makes up an Organ e.g. Heart
A group of Organs makes up a System e.g. Circulatory System
A group of Systems make up an Organism e.g. Humans
Red Blood Cell - Carries oxygen around the body
Adaptations of red blood cell: No nucleus, large surface area, so maximum area for oxygen carriers: haemoglobin
White Blood Cell ­ Fight disease, some make antibodies
Adaptations of white blood cell: Irregular shape, they can change shape to squeeze out of blood vessels and get to
the site of infection. Others have cytoplasm which can flow making it possible for the cell to change shape, surround
and engulf bacteria, can increase in numbers to fight disease.
Diffusion = movement of molecules, from a region of high concentration to a region of low concentration.
Oxygen diffuses into cells, and the waste carbon dioxide diffuses out.
Photosynthesis is the chemical change which happens in the leaves of green plants.
It is the first step towards making food.
During this reaction, carbon dioxide and water are converted into glucose and oxygen.
The reaction requires energy in the form of sunlight, and chlorophyll must also be present.
Plants are producers ­ they produce their own food
Plants produce their food via photosynthesis
Photosynthesis occurs in the leaf
Needs: Chlorophyll ­ not used up, CO2 (from the air), Water (from the soil), Sunlight energy (any light except
green light) ­ not used up
Produces: Glucose, Oxygen (waste product)
Daytime Photosynthesis & Respiration
Night-time No sunlight therefore no photosynthesis - Only respiration
Three factors limit photosynthesis from going any faster
1. Light level - Without enough light a plant cannot photosynthesise very fast, even if there is plenty of water and
carbon dioxide. Increasing the light intensity will make photosynthesis faster.
2. Carbon dioxide level - Photosynthesis can be limited by the level of carbon dioxide. Even if there is plenty of
light a plant cannot photosynthesise if it has run out of carbon dioxide.
3. Temperature - If it gets too cold the rate of photosynthesis will slow right down. If it gets too hot then plants
cease to be able to photosynthesise.
Xylems are vein like tissues that transport water and minerals up a plant.
Phloems are vein like structures through which food is transported around a plant.
Aerobic respiration
Aerobic respiration = glucose reacts with oxygen to release energy. Carbon dioxide and water are released as waste
glucose + oxygen > carbon dioxide + water + energy
C6H12O6 + 6O2 > 6CO2 + 6H2O + energy
We use the energy released from respiration for many processes.
Respiration also gives off heat, which is used to maintain our high body temperature. Our rate of respiration can be
estimated by measuring how much oxygen we use. During exercise, the body needs more energy and so the rate of
respiration increases - The breathing rate increases to obtain extra oxygen and remove carbon dioxide from the
body. The heart beats faster so that the blood can transport the oxygen and carbon dioxide faster. This is why our
pulse rate increases.
It is actually the build up of carbon dioxide that makes us breathe faster.
Anaerobic respiration
When not enough oxygen is available, glucose can be broken down by anaerobic respiration. This may happen during
hard exercise.
In humans: glucose > lactic acid + energy
Being able to respire without oxygen sounds a great idea. However, there are two problems:
· Anaerobic respiration releases less than half the energy of that released by aerobic respiration.
· Anaerobic respiration produces lactic acid. Lactic acid causes muscle fatigue and pain.
The build up of lactic acid is called the oxygen debt. After the exercise is finished, extra oxygen is needed by the
liver to remove the lactic acid.
Inside the nucleus are chromosomes
Chromosome = 1000s of coils of genes
Genes = comprise `DNA' that decides our characteristics
DNA = deoxyribose nucleic acid (chemical)
Each gene acts as a code for a particular characteristic

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The heart is a four-chambered muscular pump which pumps blood round the circulatory system.
The right side of the heart pumps de-oxygenated blood to the lungs to pick up oxygen.
The left side of the heart pumps the oxygenated blood from the lungs around the rest of the body.
1. Deoxygenated blood enters through the vena cava into the right atrium
2. It's then pumped through a valve into the right ventricle chamber
3.…read more


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