Biology Booster Topics

Paper 2• Cells• Photosynthesis and what affects it • Menstrual cycle• Carbon/nitrogen cycle

Cells and microscope

Combined Science

Paper 1

Units

Units Meters 10 ⁰= 1m

cm

mm

μm

nm

Centimeter

Millimeter

Micrometer

Nanometer

100

1,000

1,000,000

1,000,000,000

÷1000

÷1000

÷1000

÷100

Changes in microscope technology

Light microscope

• Can magnify images up to x1500

• Uses lenses and light

• Can magnify small organisms.

Labelling microscopes

Electron microscope

• Can magnify up to

x 2,000,000

• Uses beams of electrons to build up image.

• More resolution (clarity.)

• Can see sub cellular structures (organelles) in cells.

Same magnification but different resolution.

Which organelles are in animal or plant cells?

Nucleus

Cell membrane

Cytoplasm Cell wall

Chloroplast

Vacuole

Mitochondria

How are plant cells adapted?

A single bacterium

cell wall

loose genetic

material

absent from animal cells

cell

membrane

cytoplasm

present in animal cells

Bacteria can be different shapes but this diagram can

represent them.

Plant structures and function

Combined Science

Paper 2

What is photosynthesis?Plants make their own food( by photosynthesis using light energy.

light energy

‘photo’ means ‘light’

‘synthesis’ means ‘putting together’

Photosynthesis just means ‘putting together with light’.

Photosynthetic organisms are main producers of food and therefore biomass.

Word and symbol reaction

CO2 H2O C6H12O2 O2+ +6 6 6

light energy

chlorophyll

carbon dioxide + water oxygen+glucose

light energy

chlorophyll

Photosynthesis is a chemical reaction that takes place in the chloroplasts of green plant cells, where light energy is used to convert carbon dioxide and water into glucose and oxygen.

Rate of photosynthesis

Like many reactions, photosynthesis requires enzymes.

Photosynthesis is a chemical reaction and so has a rate.

light

Factors affecting the rate of photosynthesis:

carbon dioxide temperature

Factors affecting photosynthesis

Light energy has to be absorbed by chlorophyll for photosynthesis to take place. More light energy means that photosynthesis will be faster.

Carbon dioxide is one of the raw materials used by plants to make their food. More carbon dioxide means more photosynthesis, so plants make more food and grow more quickly.

Photosynthesis is controlled by enzymes, which usually work best at warmer temperatures. If it gets too hot (above 40°C), the enzymes begin to break down and are destroyed or denatured. The rate of photosynthesis decreases or even stops completely.

What is the ideal combination of factors for the maximum rate of photosynthesis?

What is a limiting factor?

enough light

How does restricting one of these facts affect the rate?

If one of the factors is restricted, the rate of photosynthesis will be reduced.

The restricted factor controls how quickly photosynthesis occurs and so limits the rate. It is called the limiting factor.

enough carbon dioxide

Water

ideal temperature (not too hot or cold).

Limiting factors

Photosynthesis is controlled by enzymes.

If it gets above or below optimum temperature the

enzymes begin to denatured. The rate of

photosynthesis decreases.

More light energy means that

photosynthesis will be faster.

More carbon dioxide means more

photosynthesis, so plants make more

food and grow more quickly.

Animal coordination, control and homeostasis

Combined Science

Paper 2

Cells in different parts of the body recognize the hormones and respond by making changes.

ovary

hormone

Hormones are chemicals that act like messengers. They are secreted by glands and carried in the blood from organ to organ.

Hormones

Glands and their hormonesMajor glands of the body:

thyroid

adrenal glands

testes (males)

pituitary gland

pancreas

ovaries (females)

Adrenal glands releases adrenalin

adrenal glands

This is to prepare the body for fight or flight; this includes:a. increased heart rateb. increased blood pressurec. increased blood flow to the musclesd. raised blood sugar levels by

stimulating the liver to change glycogen into glucose

Thyroxine controls metabolic rate as anexample of negative feedback, including:a low levels of thyroxine stimulates production of TRH (thyrotropin releasing hormone) in hypothalamusb this causes release of TSH (thyroid stimulating hormone) from the pituitary glandc TSH acts on the thyroid to produce thyroxined when thyroxine levels are normal thyroxine inhibits the release of TRH and the production of TSH

Thyroid gland releases thyroxine

Thyroid glands

RECAP: The Female Reproductive System

Day 0-5 – menstruation occurs.

The lining of the uterus wall breaks down.

Day 0-5 – Hormones oestrogen and

progesterone are at their minimum levels.

Day 5-13 – The levels of oestrogen rise, eggs

develop(matures), inside the follicle.

Day 5-13 – The increase in oestrogen causes the uterus lining to thicken with blood

vessels.

Day 14- ovulation (egg is released)

14- 28 – The levels of oestrogen fall and the

levels of progesterone rise.

Day 14-28 – Progesterone is produced by the empty follicle.

This follicle is now yellow (corpus luteum) and is withering away.

Day 14-28 – Progesterone stops the uterus wall breaking down and causes it to become more thick. The level drops near day

28.

This means the uterus wall can breakdown.

Day 0-5 – menstruation occurs. The lining of the uterus wall breaks down.

Day 0-5 – Hormones oestrogen and

progesterone are at their minimum levels.

Inside the ovaryWhat happens in the ovary during

the menstrual cycle?

Day 1-13:

egg developing

inside the

growing follicle

Day 14:

ovulation – egg

released from follicle

Day 15-28:

empty follicle turns

into corpus luteum

(yellow body)

immature

eggs

Hormones involved in fertility

The pituitary gland is a gland at the base of the brain. It releases many hormones and controls glands in the body.

The pituitary gland produces two hormones involved in fertility:

follicle stimulating hormone (FSH)

luteinizing hormone (LH).

pituitary gland

In females, the ovaries produce the sex hormones oestrogen and progesterone.

Contraceptives

Hormones to prevent pregnancy

• Hormones that control the menstrual cycle.

Barrier method

• Puts a barrier between sperm and egg so they don’t meet.

Condoms

Diaphragms- dome shaped devices that cover the cervix.

Things that prevent pregnancy. Two types

Hormonal contraception

Diabetes

Diabetes- when some people are unable to regulate their blood glucose levels because their pancreas doesn’t produce enough insulin.

Symptoms of diabetes develop quickly and can be severe. Initial symptoms include:

increased thirst, hunger and production of urine

loss of weight, tiredness and nausea.

Later symptoms include vomiting and abdominal pain. If untreated, diabetes can lead to coma and even death.

The lack of insulin means that blood glucose levels can rise dangerously high after eating, which can cause cell damage.

What is diabetes?

Controlling glucose levelsBlood glucose levels are monitored by the pancreas.

pancreas

If blood glucose levels are too high, the pancreas releases the hormone insulin. This tells the liver to convert glucose into glycogen, which is stored in the liver and muscles. If blood glucose levels are too low, the pancreas releases the hormone glucagon. This tells the liver to convert glycogen into glucose, and release it into the blood.

Type 1 Diabetes

Cause

• The pancreas doesn’t make insulin.

Treatment

• Insulin therapy- means injecting insulin into the blood.

• Reduce intake sugary food

• Regular exercise

Type 2 Diabetes

Cause

• When a person is resistant to insulin

• This means their cells don't respond properly to the hormone.

Treatment

• Can be controlled by

– Healthy eating

– Regular exercise

– Losing weight

– Medication or insulin injections.

Nitrogen and Carbon Cycles

Nitrogen cycle

Nitrogen is essential for growth because it is used by plants and animals to make proteins.

Atmospheric nitrogen needs to be changed into a useable form.

Nitrogen gas (N2) is unreactive and is not easily converted into other compounds.

Most plants can only take up nitrogen in the form of ammonia or nitrate.

Nitrogen cycle

Nitrogen cycle role

Into ammonia

Into ammonia

Why is carbon important?

What happens to the carbon in organisms when they die?

The carbon from dead organisms can also form fossil fuels and sedimentary rocks such as limestone. These are long-term carbon stores.

As dead matter decomposes, carbon is released back into the atmosphere in the form of carbon dioxide.

Plants use carbon dioxide duringphotosynthesis to produce sugars. The carbon is then transferred to animals along food chains.

Carbon cycle