BIOLOGY UNIT 2

Animal Cells: Cytoplasm, Ribosomes, Mitochondria, Cell membrane, membrane, nucleus

Plant Cells: Cell wall, nucleus, cell membrane, mitochondria, ribosomes, cytoplasm, chloroplasts, permanent vacuole.

Root Hair: Tiny hair like structure means bigger surface area to absorb water&ions
Palisade Cells: Column shaped cells packed with chloroplasts for photosynthesis.
Xylem: Long, thin hollow structures transport water through the sten and root.
Nerve cells: have long axons that carry across nerve impulses.
Ovum cells: Larger than other cells to carry food reserves for embryos.
Sperm cells: Mobile cells as they have tails.
Red Blood Cells: No nucleus to carry haemoglobin to carry oxygen
White Blood Cells: Changes shape to engulf and destroy enzymes.

Because cells are living things, they constantly have to replace substances which are used up and have to remove wasre which accumulates.

Definition: Diffusion is the spreading of a gas, or of any substance in solution, which results in moving from a high concentration to a low concentraion.

The greater the difference in concentration the faster the rate of diffusion.

Osmosis is a more tricky subject.

Definition: The net movement of water from a high concentration to a low concentration through a partially permeable membrane.

The effect of osmosis is to gradually dilute the solution. This is what happens at root hair cells, where water moves from the soul into the cell by osmosis, along a concentration gradient.

4 things are needed for photosynthesis:
LIGHT
CARBON DIOXIDE
WATER
CHLOROPHYLL

Equation:
Carbon Dioxide + Water ---------------------------> Glucose + Oxygen 
                                           light + chrlorophyll

Temperature:
When the temperature reaches 45 degrees the enzymes controlling photosynthesis start to be desroyed and the rate of photosynthesis drops to zero.

Carbon Dioxide Concentration:
Carbon Dioxide goes up then levels out which shows it isnt the limiting factor anymore.

Light Intensity:
Light intensity goes up then also levels out which shows something else is the limiting factor.

Nitrates: Needed to make amino acids used to make proteins, stunted growth.
Magnesium: Make chlorophyll , shortage leads to yellow leaves.

The transfer of energy can be transfered along a food chain in the form of biomass as the energy is stored in the cells of the plant/animal.

Pyramids of Biomass
When drawing a pyramid of biomass it goes bigger to smaller and always draw the arrow showing the direction of flow of energy.

Biomass and energy are lost at every stage of the food chain because it is lost in respiration, waste and heat.

Particularly warm blooded animals who need to have warmer bodies higher than the temperature.

We can increase the efficiency of food production by reducing tge number of stages in a food chain or by limiting an animals movement and controlling its temperature.

This means battery hens and pig pens. However, some people find this type of rearing unacceptable even though more of the food eaten by the animal is converted into biomass because less heat is lost through:

• heat
• movement

1. Starts off with CO2 in the atmosphere.
2. Plants absorb the CO2 via photosynthesis.
3. Result of this is Carbon Containing Compounds which are consumed by animal.
4. Animal respires releasing CO2 back into the atmosphere.
5. Animal and plants die and microorganisms feed on their bodies.
6. These detrivores and microorgansims respire releasing CO2 into the atmosphere.

Enzymes are biological catalysts that speed up the rate of any particular chemical reaction. They are made of amino acids.

High temperatures denature enzymes this is why it is dangerous for a human's body temperature to go higher than 37 degrees.

Enzymes speed up respiration, protein synthesis and photosynthesis eg.

Energy released during resperation:
Build larger molecules using smaller ones.
Enable muscles to contract
Maintain a constant temperature(in mammals and birds)
Make proteins in plants from amino acids

Aerobic respiration releases energy through the breakdown on glucose molecules, by combining them with oxygen inside living cells.

Glucose + Oxygen --------------------------> Carbon Dioxide+ Water + Energy
                               catalysed by enzymes

Thats all you basically need to know about this Sub topic.

Salivary Glands- produce amylase which digests starch to make sugars

Stomach- makes protease which digests protein to make amino acids.

Pancreas-makes lipase to digest fats to make fatty acids and glycerol.
Pancreas-makes protease to digest proteins to make amino acids.
Pancreas-makes amylase to digest starch to make sugars.

S.Intestine-makes lipase to digest fats to make fatty acids and glycerol.
S.Intestine-makes protease to digest proteins to make amino acids.
S.Intestine-makes amylase to digest starch to make sugars.

The function of Bile is:

1.It neutralises the stomach acid which is added to food in the stomach to produce alkaline conditions in which the enzymes of the small intestine work best.

2. It emulsifies fat from large droplets to small droplets to increase the surface area. It enables the lipase enzymes to work faster.

IT IS PRODUCED IN THE LIVER AND THEN STORED IN THE GALL BLADDER BEFORE BEING RELEASED INTO THE SMALL INTESTINE..

In the home

• Protease enzymes break down blood and food.
• lipase enzymes enzymes break down oil anmd grease stains in washing up powder.

In industry

• Protease used to pre-digest protein in baby foods.
• Carbohydrates are used to convery starch into sugar syrup.
• Isomerase used to convert glucose into fructose, ideal for slimming foods as it is sweeter than glucose which means less needs to be used.

The water content, ion content, temperature and blood sugar levels need to be controlled.

Too much water may move into or out of the body by osmosis causing damage. Water and ions enter the body via food and drink.

Blood concentration is monitored and controlled by the pancreas which secretes the hormone insulin. The insulin converts the glucose into insoluble glycogen in the liver and removes it from the blood.

If the pancreas does not produce any or enough insulin then it may cause Diabetes. There are two types.

Type 1: Careful attention to diet and injecting insulin.
Type 2: Careful attention to diet.

Too hot

• Vasodilution- blood vessels dilate and increase heat loss by radiation
• Sweat glands release sweat which evaporates causing cooling.

Too Cold

• Vasoconstriction- blood vessels constrict, decreases heat loss by Radiation.
• 'Shivering' heat energy is released via respiration in the cells.

Body cells contain 46 chromosones arranged as 23 pairs. Chromosones are made up of large molecules of DNA. A gene is a section of DNA.

In females the sex chromosones are identical and called the X chromosones.
In males one is much shorter than the other. The short one is the Y chromosone.

**-Female
Xy-Male

Like all pairs of chromosones, offspring inherit one from the mother and one from the father. Therefore, the sex is decided on the y sperm or x sperm.

Mitosis
Is the division of body cells to produce new cells. This occurs for growth and repair. Before the cell divides, a copy of each chromosone is made so the new cell has the same genetic information. This means that the cells of asexually reproduced offspring contains the same genes as the parents.

1.Parental cell with two pairs of chromosones
2.Each chromosone replicates itself.
3.The copies are pulled apart, cell divides for the only time.
4.Each 'daughter' cell has the same number of chromosones as the parent cell and contains the same genes.

1. The egg and the sperm come together.

2. They fertlise together.

3.A parental cell with two pairs of chromosones.
            MITOSIS TAKES PLACE see previous slide
4. Development of new individual.

This occurs in the testes and ovaries to produce the gametes(sex cells) for sexual reproduction.

1. Cell with two pairs of chromosones.
2. Each chromosone replicates itself
3. Chromosones part to opposite sides with their 'copies'.
4. Cell divides for the first time
5. The copies now seperate and the second cell division takes place
6. Four gametes each with half the number of chromosones of the parental cell.
   aka. it has 23 chromosones because the other 23 come from the mother.

Some genes have different variations or forms these are called alleles. In a pair of chromosones, the alleles for a gene can be the same or different. If they are different, then one allele will be Dominant and one will be Recessive.

The dominant allele controls the characteristics of the gene. The recessive allele will only control the charateristics of the gene if two are present on both chromosones in a pair.

Dominant allele- RR
or
Homozygous Dominant-RR

Recessive allele-rr
or
Homozygous Recessive-rr

However , heterozygous dominant Rr can also happen

Huntingtons disease
It is a disorder of the nervous system caused by a dominant allele. It can be passed on by only one parent who has the disorder.

Cystic Fibrosis
Cystic fibrosis is a disorder of cell membranes caused by a recessive allele. It must be inherited from both parents who can be carriers without having the disorder themselves.