Biology B2

Plant + animal cells:

Nucleus - contains genetic material

Cyptoplasm - gel-like substance where chemical reactions happen

Cell membrane - holds cell together + controls what goes in and out

Mitochondria - reactions for respiration occur

Ribosomes - where protiens are made in the cell

Only in plants: 

Cell wall - supports cell

Permanent vacuole - contains cell sap

Chloroplasts - photosynthesis occurs and contains chlorophyll

The spreading of particles from an area of high concentration to area of low concentration

Occurs in solutions and gases

bigger difference in concentration = faster diffusion rate

Allows substances to move in and out of cells

Oxygen reguired for respiration uses diffusion

Examples of specialized cells:

Palisade cells packed with chloroplasts for photosynthesis

Guard cells have special shape

Red blood cells have concave shape to increase surface area

Similar cells - tissues - organs - organ systems - large multicellular organs

Differentiation - cells becoming specialised

Photosynthesis - plants and algae producing (food) glucose using sunlight

Chrorophyll - absorb sunlight

Carbon dioxide + water --- glucose + oxygen

During photosynthesis:

1) Light energy absorbed by chloroplasts in chlorophyll

2) This energy is used by converting carbon dioxide and water into glucose

3) Oxygen released as a by-product

Affected by:

Light intensity

Avaliability of CO2 

Temperature - increases rate of photosynthesis until 45 degrees where enzymes denature

To create conditions:

Use greenhouses to trap suns heat and allow light

Can produce CO2 and light

For respiration

Produces cellulose to strengthen cell walls

Making protiens

Can be turned into fats

Stored in roots as starch for when photosynthesis can't occur

Catalysts produced by living things

Are protiens made from amino acids

Cause only useful reactions unlike heat that causes bad reactions aswell

Each enzyme has special shape the fits with a particular substance in a reaction that cause the substance to split in two

Optimum pH = 7

Optimum temperature before denaturing = 37

Starch protiens and fat are too big to pass through digestive system so digestive enzumes break them down

Amylase converts starch into sugars in the salivary glands, pancreas and small intestine

Protease converts protiens into amino acids in the stomach, pancreas and small intestine 

Lipase converts lipids (fats + oils) into glycerol + fatty acids in the pancreas + small intestine

Bile - produced in the liver and stored in gall bladder before being released into the small intestine, neutralises acids from stomach to provide alkaline conditions in the smal intstines

Hydrochloric acid produced by stomach

Enzymes used in homes as biological detergents

Enzymes used in industry as carbohydrates convert starch into sugar syrup, advantages are specific but disadvantages are can be contaminated

Respiration is the process of releasing energy from glucose in every body cell

Aerobic respiration: 

Respiration using oxygen

Glucose + oxygen --- carbon dioxide + water + energy

Mainly occurs in mitochondria

Used to allow muscles to contract and maintain body temperature

Aenerobic Respiration:

Respiration without oxygen

Glucose --- energy + lactic acid

Causes lactic acid build up and doesn't release as much energy as aerobic

You breathe heavily after excercise to get oxygen into blood

Exercise requires more glucose and oxygen to be supplied to the muscle cells which requires blood to flow faster

Some glucose is stored as glycogen which is converted back to give more energy when required

Energy increases breathing rate and the speed the heart pumps

Chromosones:

The 23rd pair of chromosones decide your gender, x+y = male and x+x = women

Long molecules of DNA 

Found in nucleus

Gene: 

Section of DNA

Tells cells what order to put amino acids in to make protiens

Makes new cells for growth and repair in asexual reproduction

The cell replicates itself by splitting to form identical offspring

1) DNA duplicates itself to form x's

2) Chromosones line up at the centre and x's pulles apart

3) Membranes form around two sets of chromosones

4) Two new identical cells formed

Occurs in testes and ovaries to form gametes

Gametes have half the number of chromosones which results in genetic variation

Meiosis involves two divisions

1) Cell duplicates DNA 

2) Cell splits down the middles

3) Chromosones line up iin cell

4) End up with 4 gametes with a single set of chromosones

Embryonic stem cells can turn into any type of cell

May be able to cure diseases by replacing faulty cells

Controversial as people feel embryos shouldn't be used for research as they are human cells

Concluded that:

Characteristics in plants are determined by hereditary units

Hereditary units can be dominant and recessive

If both dominant expressed they can be passed on from each parent

1) From gradual replacement by minerals (most common) where things like bones and teeth that don't easily decay go into the ground and are replaced by minerals that leave a distinctive shape

2) From casts and impressions where an organism is buried in soft material like clay and when the clay hardens a cast of the material is left

3) From preservation in places where decay occurs such as glaciers where it's to cold for microbes to work

Extinction occurs because:

The enviroment changes too quickly e.g. destruction of habitat

A new predetor kills them e.g. humans

A new disease kills them

Have to compete with other species for food

Catastrophic event occurs e.g. astroid

Speciation - the development of a new species that can't reproduce for fertile offspring with old species

1) Physical barrier seperates two species

2) The seperated organisms adapt to surrounding 

3) Adapt so much that they cant reproduce for fertile offspring

Alleles are dominant or recessive:

• the characteristic controlled by a dominant allele develops if the allele is present on one or both chromosomes in a pair
• the characteristic controlled by a recessive allele develops only if the allele is present on both chromosomes in a pair

For example, the allele for brown eyes is dominant, while the allele for blue eyes is recessive. An individual who inherits one or two alleles for brown eyes will have brown eyes. An individual will only have blue eyes if they inherit two copies of the allele for blue eyes.