Key Concepts In Biology

Question 1

What’s in animal cells and what are their functions

Answer 1

Nucleus-contains genetic material that controls the cell.
Cytoplasm-where most of the chemical reactions happen.
Cell membrane-holds the cell together and controls what goes in and out
Mitochondria-where most of the reactions for respiration takes place
Ribosomes-involved in the translation of genetic material in protein synthesis

Question 2

What is in a plant cell and what are their functions

Answer 2

They have the same as animal cells and:
Cell wall-supports the cell and strengthens it
Large vacuole-contains cell sap and maintains the internal pressure
Chloroplasts-wher photosynthesis occurs

Question 3

What are the parts of bacteria cells and what are their functions

Answer 3

Chromosomal dna-controls the cells activity and replication
Ribosomes
Cell membrane
Plasmid dna-small loops of extra dna for drug resistance and can be passed between bacteria
Flagellum-rotates to make the bacteria move

Question 4

Egg cell structure

Answer 4

It contains nutrients in the cytoplasm to feed the embryo
It has a haploid nucleus
Straight after fertilisation it’s membrane changes structure to stop any more sperm getting in. This makes sure the offspring end up with the right amount of dna.

Question 5

Sperm cell structure

Answer 5

Long tail so it can swim to the egg
Has lots of mitochondria in the middle section to provide the energy to swim
Has acrosome at the front of the head where it stores enzymes needed to digest its way through the membrane of the egg cell
It also contains a haploid nucleus

Question 6

Ciliated epithelial cell structure

Answer 6

Line the surface of the organ
Have cilia on the top surface of the cell
The cilia beat to move substances in one direction along the surface of the tissue
Lining of the airways contain ciliated epithelial cells help to move mucus up the throat so it can be swallowed

Question 7

What are he differences between light microscopes and electron microscopes

Answer 7

Light microscopes work by passing light through the specimen and lets you see the nuclei and chloroplasts.
Electron microscopes work by passing electrons through a specimen. They have a higher magnification and resolution than light microscopes so you can see smaller things such as mitochondria

Question 8

How to calculate magnification

Answer 8

Magnification = eyepiece magnification*lens magnification

Image size/real size

Question 9

How are proteins carbohydrates and fats broken down

Answer 9

Carbohydrate>sugars
Proteins>amino acids
Fats>glycerol and fatty acids

Question 10

How to test for sugar starch and lipids

Answer 10

Starch-iodine
Sugar-Benedictus solution
Lipids-emulsion test
Proteins-biuret test

Question 11

How to calculate energy in the food

Answer 11

Energy in food=mass of watertemp change of water4.2

Question 12

What are the 4 stages of mitosis

Answer 12

Prophase-the chromosomes condense getting shorter and fatter.The membrane around the nucleus breaks down and chromosomes lie free.
Metaphase-the chromosomes line up at the centre of the cell
Anaphase-cell fibres pull the chromosomes apart and go to each end
Telophase-membranes form around each of the sets of chromosomes these become the nuclei and the nucleus has divided.
Cytokinesis-the cytoplasm and cell membrane divide to form 2 cells

Question 13

What is cell differentiation and cell elongation

Answer 13

Cell differentiation-the process by which a cell changes to become specialised for its job.
Cell elongation-the plant cell expands making the cell bigger and making the cell grow.

Question 14

What are the 2 types of stem cells and what are their functions

Answer 14

Embryonic stem cells-have the potential to divide and produce any kind of cell
Stem cells-they can’t produce any cell type only certain ones which are used to replace damaged cells.

Question 15

Where are plant stem cells found

Answer 15

Plant stem cells are found in meristems which are found in roots and shoots. They produce unspecialised cells and can form any cell type.

Question 16

What are the uses of adult stem cells

Answer 16

They can be used to cure some diseases such as sickle cell anaemia. It might be possible to use stem cells to create specialised cells to replace damaged cells

Question 17

What are the different parts of the brain and what are their functions

Answer 17

Cerebrum-the largest part of the brain. Divided into 2 hemispheres. The right controls muscles on the left side of the body and vice versa.
Cerebellum-responsible for muscle coordination and balance
Medulla oblongata-controls unconscious activities like breathing and your heart rate

Question 18

How does the central neurone system work

Answer 18

When a stimulus is detected by receptors the information is then converted to a nervous impulse and sent along sensory neurones to the cns.The cns coordinates the response and the impulse travels along relay neurones and the cns sends information to an effector

Question 19

What is a synapse

Answer 19

The connection between 2 neurones is called a synapse. The nerve signal is transferred by chemicals called neurotransmitters which diffuse across the gap. The neurotransmitters set of a new electrical signal to the next neurone. Th transmission is slowed down by the synapses.

Question 20

What are the different parts of the eye

Answer 20

Cornea-reflects light into the eye
Iris-controls how much light enters the pupil
Lens-refracts light focussing it onto the retina.
Retina-the light sensitive part and is covered in receptor cells call d rods and cones which detect light. Rods are more sensitive in the dim light but can’t sense colour. Cones are sensitive or different colours but are not so good in dim light.
The information from light is converted into electrical impulses.

Question 21

What causes long and short sightedness

Answer 21

Long sightedness occurs when the lens is in the wrong place and doesn’t bend th light enough or the eyeball is too short. Light from near objects is brought into focus behind the retina. Glasses with a convex lenses correct it.
Short sightedness occurs when the lens is in the wrong place and bends the light too much or the eyeball is too long. Light from distant objects is brought into focus in front of the retina. Glasses with concave lenses correct this.

Question 22

Sexual reproduction and meiosis

Answer 22

A male gamete fuses with a female gamete and produces a zygote with the full set of chromosomes. The zygote undergoes cell division and develops into an embryo.

Question 23

How does meiosis work

Answer 23

Before the cells divide it duplicates it’s dna. In the first division the chromosomes line up in Paris in the centre of the cell one chromosome in each pair form the mum and 1 from the dad. The pairs are pulled apart so each new cell has one copy of each chromosome. Each new cell will have a mixture of the mothers and fathers chromosomes creating genetic variation

Question 24

What is the second division in meiosis

Answer 24

The chromosomes line in up again and the arms are pulled apart. You get four haploid daughter cells - these are the gametes. Each gamete only has a single set of chromosomes and are genetically different from each other.

Question 25

What is dna made of

Answer 25

Dna strands are polymers made up of lots of repeating nucleotides. Each nucleotide consists of one sugar molecule on phosphate molecule and one base. One of 4 different bases join to each sugar adenine thymine cytosine guanine. A dna molecule has 2 strands coiled together in a double helix shape. Each base links to a base on the opposite strand. A with T and C with G. The base pairs are joined together by weak hydrogen bonds.

Question 26

What did Mendel conclude

Answer 26

Characteristics are determined by hereditary units.
Hereditary units are passed on to offspring unchanged from both parents.
Hereditary units can be dominant or recessive

Question 27

Sex linked genes

Answer 27

Men only have one X chromosome and often have one allele for sex linked genes.
Because men only have one allele the characteristic is shown even if it is recessive which makes men more likely than women to show recessive characteristics for genes that are sex linked.

Question 28

What causes variation

Answer 28

Genetic variation can be caused by organisms having different allele which lead to differences in phenotype. Or by new alleles rising through mutations as well as sexual reproduction causes genetic variation since it results in alleles being combined.
Variation can be caused by the environment for example a plant grown on a sunny windowsill could grow green whereas the same plant grown in darkness would grow tall and spindly and the leaves would turn yellow.

Question 29

How does natural selection work

Answer 29

Individuals show genetic variation
Predation competition and disease affect chance of survival and reproducing
Certain characteristics make them better adapted to survive
The less well adapted are less likely to survive
Beneficial characteristics become more common

Question 30

Evidence for evolution

Answer 30

Tools become more complex as time goes on

Question 31

What are the 5 kingdoms

Answer 31

Animals fish mammals reptiles
Plants grasses trees
Fungi mushrooms and toadstools
Prokaryotes single celled organisms without nucleus
Protists eukaryotic single cell organisms

Question 32

What are the 3 domains

Answer 32

Archaea similar to bacteria
Bacteria contains true bacteria
Eukarya fungi plants animals protists

Question 33

What is selective breeding

Answer 33

Selective breeding is when humans artificially select the animals and plants to breed. The process:
Select the characteristics you’re after
Breed them together
Select the best of the offspring
Continue the process over generations

Question 34

Advantages and disadvantages of selective breeding

Answer 34

Advantages
Some animals have better characteristics for producing meat. Using these in selective breeding means the meat yields are high.
Disadvantages
It reduces the gene pool
Inbreeding can cause health problems because there’s more chance of of inheriting genetic defects.
If a new disease appears there’s less chance of resistance alleles

Question 35

How genetic engineering works

Answer 35

The dna you want to insert is cut out using a restriction enzyme the vector dna is cut using the same enzyme.
The vector dna and dna inserting are left with sticky ends and mixed together in ligase enzymes.
The recombinant dna is inserted into other cells.
These cells now use the gene inserted to make the protein you want

Question 36

What are the benefits of gm crops and how they work

Answer 36

They can make crops resistant to insect pests
The toxin is inserted into crops which produce the toxin their stems and leaves making them resistant. The toxin is specific to pests and is harmless to humans.

Question 37

What is health

Answer 37

Health is a state of complete physical mental and social well being

Question 38

What is the difference between communicable or non-communicable

Answer 38

Communicable can be spread between individuals

Non communicable can’t be transmitted between individuals

Question 39

What is the lytic pathway

Answer 39

The virus attaches itself to a specific host cell and injects its genetic material into the cell.
The virus uses proteins and enzymes in the host cell to replicate its genetic material and produce the components of new viruses
The viral components assemble
The host cell splits open releasing the new viruses

Question 40

What is the lysogenic pathway

Answer 40

The infected genetic material is incorporated into the genome of the host cell.
The viral genetic material gets replicated along the host dna every time the host cell divides but the virus is dormant
Eventually a trigger causes the viral genetic material to leave the genome and enter the lytic pathway

Question 41

Plant defences against pathogens

Answer 41

Physical- a waxy cuticle provides a barrier to stop pathogens entering them or pests from damaging the. Plant cells are surrounded by cell walls made from cellulose which form a physical barrier.
Chemical- they produce antiseptics which kill bacterial and fungal pathogens. They also produce chemicals to deter pests.

Question 42

Physical and chemical barriers in the body

Answer 42

The skin is a barrier and if it is damaged blood clots to seal cuts and keep microorganisms out.
Hairs and mucus in your nose trap particles that could contain pathogens
Cells in your trachea and bronchi produce mucus which traps pathogens. The trachea has cilia which waft the mucus up to the back of the throat.
The stomach produces hydrochloric acid which kills pathogens that were swallowed.
The eyes produce lysozyme which kills bacteria on the surface of the eye.

Question 43

How do antibiotics work

Answer 43

They inhabit processes in bacterial cells but not in the host. Some anti bacteria inhibit the building of bacterial cell walls this prevents the cells dividing and kills them. Different antibiotics kill different types of bacteria. Antibiotics don’t destroy viruses because viruses reproduce using your body cells.