Biology Additional (B2)

Parts of a cell

DNA Structure A DNA molecule has 2 strands coiled together in a double

helix shape. These strands are held together by bases.

There are 4 bases:

These bases are joined together in the same way (A-T, G-C). This is known as

base pairing. These base pairs are joined together by weak hydrogen bonds.

Discovery of DNA

DNA Extraction

Protein Synthesis Genes are sections of DNA that code for the sequence of amino acids in a

protein. A gene can be broken down into Codons. These are sections of three

basses.

A gene is like a cook book and codons are like the recipe. The gene does not

create the protein, it just provides the information of how to make it. The chef

in this case is a ribosome.

Transcription

1) DNA unzips

2) Each codon codes for the bases on the mRNA

3) Where A would normally code for T, on mRNA it codes for U

Translation

1) mRNA joins the ribosome

2) The anticodons on the tRNA are attracted to the

complementary codons on the mRNA. Specific amino acids are

attached to the tRNA.

3) The amino acids then form peptide bonds

4) The tRNA will then detach from the amino acid and get some

more of the same amino acids

Enzymes Enzymes are biological catalysts. This means they help to speed up biological

processes.

An enzyme has an area called an active site.

This area is complementary to the target

molecule called the substrate. This

active site holds the substrate under

pressure so that it becomes easier for it to be broken down into its

products.

Enzymes are affected by 3 things:

Temperature

PH

Substance Concentration

GMO A GMO is a genetically modified organism. This means a gene has been

removed from one organism and placed into another organism’s genome.

This can be done by:

1) Find the desired gene

2) Use restriction enzymes to cut the DNA out,

ensuring the cut is jagged and therefore leaves

sticky ends

3) Make another cut in the new DNA in order to paste

the new gene using ligase enzyme.

Scientist modify the plasmid as it is less tangled up and therefore can be

modified easier.

Mitosis and Meiosis

Cloning an Animal

1) Remove the diploid body cell from the animal you want to clone.

2) Then remove the nucleus from both cells.

3) Place the diploid nucleus into the haploid cell

4) Give it an electric shock in order to stimulate the division.

5) Then place the cells into a surrogate sheep.

6) The baby born will be an exact clone of the original animal.

Stem Cells The cells in the embryo are all the same and are called embryonic stem cells.

Stem cells can divide into any type of cell. Becoming a specialised cell is called

differentiation. Stem cells could be used to cure diseases. Stem cell research is

banned in many countries.

Aerobic Respiration

Anaerobic respiration

Calculating cardiac output

Diffusion Particles moving from where there is a high

concentration gradient to where there is a low

concentration gradient.

Example

One use of this is when we breathe in oxygen. There is less oxygen in the

capillary this means that will oxygen will diffuse into the capillary in order to

make there be an equal amount in the alveoli and in the capillary. There is also

more carbon dioxide in the capillary than in the alveoli. This causes the carbon

dioxide to diffuse into the alveoli and then into the atmosphere.

Photosynthesis

Leaves have little holes called stomata. This can let gasses in and out. It also

lets water vapour escape. This is called transpiration.

Active Transport When particles move from where there is a low

concentration gradient to where there is a high

concentration gradient. This requires energy.

Example

Root hair cells in plants require minerals

from the soil. To get these minerals

diffusion cannot be used as there is

already a higher concentration in the cell

than in the soil. To get the minerals there

are carrier proteins on the surface of the

root hair cells. Minerals will bond with the

protein. The protein then uses energy to open up and bring the nutrients into

the cell.

Osmosis The movement of water

molecules from a high to low

concentration across a semi-

permeable membrane. A

semi-permeable membrane is

a membrane that has small

gaps in it. This means that

small particles can fit through but larger wans can’t. Pure water has a higher

concentration than water with solutes such as salt in it.

Xylem Carries water and minerals from the roots.

Phloem Carries sugar from leaves to growing tissue and storage tissue.

Looking at the distribution of organisms

Pooters

Pitfall traps

Sweep nets

Pond nets

Quadrat

Evidence for evolution Fossils

Pentadactyl limb

Cell organisation

The Heart and the Circulatory System

Adaptations of the Heart:

Valves prevent backflow of blood

Left ventricle wall is thicker. This is because more muscle is needed to

pump the blood around the whole body

Double pump. Makes sure blood pressure stays high

Septum separates oxygenated blood from deoxygenated blood

The Blood The blood contains:

Red blood cells –

o Adaptations- Dips in the middle. This increases surface area,

allowing for more oxygen to be absorbed.

o Haemoglobin- Contains 4 iron atoms to carry oxygen

o No nucleus. This means there is more space for oxygen

White blood cells-

o Can change shape to engulf pathogens.

o They have a complimentary shape to the pathogens. This means

they can easily fight them with the antibodies and antitoxins they

produce.

Platelets-

o Made up of broken bits of cells. This irregular shape helps to clog

up any wounds in order for them to heal

Plasma-

o Can carry waste materials away from cells such as

Carbon dioxide

UREA

o Can carry useful materials to cells such as

Red blood cells

White blood cells

Platelets

Glucose

Amino Acids

Hormones

Antibodies and Antitoxins

Blood Vessels

Arteries-

Veins-

Capillaries-

Digestive System

Digestive enzymes

Investigating digestive enzymes

1. Visking tubing can be used to represent the gut.

2. A starch and amylase solution can be added. Starch is too big to

leave.

3. The tubing can then be placed in a boiling tube full of water.

This water represents our blood stream.

4. Benedict’s solution tests for the presence

of sugar. Iodine tests for starch. After 0 mins,

the water should not change the colour of the solutions.

After 15 mins, the amylase will have time to break down the

starch. There should be no starch in the water as it’s too big

to fit through. The benedict’s solution should change to brick

red because the starch has been broken down into sugar. This can fit

through the tubing and will therefore be present in the water

Functional Food