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72 Cards in this Set

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What do electron microscopes do?

Pass a beam of electrons through a cells to allow us to see much more detail than conventional microscopes.

What is the equation to work out the magnification of a light microscope?

magnification = magnifying power of eyepiece


x


magnifying power of objective lens

What is resolving power of a microscope?

The power that determines how clear the image is. The greater the resolving power, the clearer the image.

What are the four components of an animal cell?

Cytoplasm, nucleus, mitochondria, cell membrane

What are the seven components of a plant cell?

Cytoplasm, nucleus, mitochondria, cell membrane, cell wall, vacuole, chloroplasts

What are the five main components of a bacterial cell?

Cytoplasm, cell membrane, cell wall, plasmid DNA, some have a flagellum

What is the job of cytoplasm?

It is where most of the cell's reactions take place

What is the job of a cell membrane?

To control the movement of chemicals in and out of the cell

What is the job of the nucleus?

It contains chromosomes which have genes

What is the job of mitochondria?

Where sugars are broken down to release energy

What is the job of a cell wall?

To strengthen the cell

What is the job of the vacuole?

To keep the cell turgid (rigid)

What is the job of chloroplasts?

They contain chlorophyll to be used in photosynthesis to produce food

What are chromosomes?

They are long strands of DNA wrapped around a protein molecule

What is a nucleotide?

A building block for cells, in DNA strands. Each nucleotide contains one of the four bases

What are the four bases and which do they pair with?

Adenine pairs with Thymine


Cytosine pairs with Guanine

What is gene?

A section of DNA which carries information that enables cells to make proteins

How can DNA be extracted from a cell? (Three steps)

1) Use a detergent mixture to break the membrane of the cells and release chromosomes


2) Use a protein-digesting enzyme to break down the protein of the chromosomes


3) Add cold methanol, which precipitates the DNA so it can be clearly seen

What is complementary base pairing?

The arrangement where two strands of DNA are joined by their bases by weak hydrogen bonds

What is a codon?

A sequence of three bases which specifies a particular amino acid

What is genetic engineering?

Transferring genes from one organism to another

How are GE cells made?

They are grown in a culture solution in a huge fermenter

What are three advantages of GE insulin?

- cheap to produce


- it is human so won't cause allergic reactions


- it doesn't use animal products so doesn't raise ethical issues

What are five GM crop developments?

Crops that can:


- grow in places of low rainfall


- produce their own pesticides


- resist diseases


- resist herbicides


- produce their own fertiliser

What are four reasons that people are worried about GM crops?

- it isn't natural


- it may affect our health


- they may harm wildlife


- pollen from herbicide resistant crops could transfer to weeds

What is golden rice?

A GM form of rice that produces more beta-carotene which our cells convert to vitamin A. It is used to combat vitamin A deficiency, a common problem in poorer countries

What is meiosis?

A form of sexual reproduction which produces genetically different offspring. It produces four haploid daughter cells, each of which receives half of the parent cell's chromosomes.

What is mitosis?

A form of asexual reproduction which produces genetically identical offspring. It produces two diploid daughter cells, both with a full set of 46 chromosomes.

What is mitosis used for?

Growth and to repair damage because the daughter cells are identical

What is meiosis used for?

The production of gametes (sex cells)

What is vegetative reproduction?

Asexual reproduction in plants where a part of a leaf or stem grows into a new, gentetically identical plant

What is tissue culture?

A process of cutting tissue from a parent plant, then growing it in sterile liquid or gel

What are the four stages of cloning an animal?

1) Donor eggs are taken from females and fertilised in a laboratory


2) Each embryo splits into its separate cells


3) Some of the cells are transferred to the host mother's womb


4) The host mother gives birth to several genetically identical clones

What are two benefits and one negative of cloning animals?

B1 - animals with desirable characteristics can be produced quickly


B2 - It can help to build up populations of rare animals


N1 - cloned animals can live short and painful lives thanks to medical problems

Describe embryonic stem cells

They are unspecialised cells (don't do a specific job) found on the inside of an embryo. As they develop, they differentiate and change into different types of specialised cells

What is stem cell therapy?

Making stem cells multiply and differentiate so that we have an unlimited supply of cells which can be transferred into people with damaged tissue

Why is stem cell therapy unethical?

Because taking stem cells from an embryo will destroy the embryo and some people think that it is wrong to do this

What are three risks of stem cell therapy?

- rejection of the stem cells


- the cells could carry genetic mutations


- side effects could be caused in the recipient such as immune responses or the development of cancer

What is a genome?

All the DNA in each of an organisms's cells

How do cells synthesise proteins?

By joining amino acids together in the correct order

What is RNA?

Ribonucleic acid, it is similar to DNA but made up of only one strand and has a Uracil base instead of Thymine

What are the two types of RNA and what are their roles?

mRNA - messenger RNA - carries protein making information to the ribosomes




tRNA - transfer RNA - carries the amino acids to the ribosomes

What are the two stages of protein synthesis?

Transcription, translation




To remember their order: think WW2 in England!


First there was conscription to get soldiers.


Then, the war ended, and a treaty was made so translators were needed

What happens in transcription?

DNA strands separate, and mRNA strands form as RNA combines with the strands of DNA. Then, the strands of mRNA separate from the DNA and pass out of the nucleus to the ribosomes in the cytoplasm

What happens in translation?

The mRNA strands bind to a ribosome, forming an mRNA-ribosome complex. Each tRNA molecule binds to an amino acid in the cytoplasm depending on its codon, and these combinations pass through to the complex. The tRNA bases bind with mRNA bases and bonds form between the amino acids. The tRNA and mRNA strands then separate from the amino acids, and the resulting chain forms a polypeptide (protein)

How are mutations harmful?

The mutated proteins disturb the activity of the cell

How do mutations occur?

Due to copying errors in DNA replication. A base may be inserted or deleted which changes the sequence of bases

What is a silent mutation?

When a mutation changes a codon to an alternative codon which still specifies the same amino acid and therefore has no effect on the protein made

How are enzymes specific?

Each enzyme can only catalyse one reaction

How do enzymes work?

The enzyme fits together with a substrate to make an enzyme-substrate complex. They bind at the part called the active site and the enzyme breaks down the substrate into other products

What factors affect the activity of enzymes?

Temperature and pH


Higher temp = higher activity, but this will change at around 37 degrees which is optimum temp


Optimum pH will change depending on the enzyme

What is denatured?

It is when an enzyme stops working because it has been subjected to heat and pH that are too high. It causes the molecules shape to be permanently changed so that it can no longer bind with its target substrate

What is aerobic respiration?

Respiration using oxygen to break down glucose into energy, CO2 and water




Glucose + oxygen -> energy + carbon dioxide + water

What is anaerobic respiration?

Respiration without oxygen




Glucose --> lactic acid + oxygen




It happens during exercise because the body can't take in enough oxygen

What is EPOC?

Excess Post-exercise Oxygen Consumption




It is when more air is drawn in after exercise to break down the lactic acid in the muscles

What is recovery period?

It is the time it takes for the lactic acid to be removed and breathing to return to normal

What is diffusion?

When molecules in liquids or gases move from an area of high concentration to one of low concentration

What is a concentration gradient?

The difference in concentration of a substance between high and low concentration gradients

What is the photosynthesis equation?

CO2 + Water ---> Glucose + Oxygen

How does the structure of leaves help photosynthesis?

Palisade cells contain chloroplasts containing chlorophyll for photosynthesis. There are spaces in the leaf to allow gases to circulate and reach the cells that need them. Stomata in the underside of the leaf allow specific gases in and out of the leaf

What factors affect the rate of photosynthesis?

Temperature, light intensity, carbon dioxide, water

What is a limiting factor?

A factor that will have a negative impact on the rate of photosynthesis if it changes

What is a xylem?

A tube of hollow, dead cells that carries water and dissolved mineral salts from a plant's roots, up the stem

What is a phloem?

Similar to a xylem, but carries dissolved glucose to the parts of the plant. The glucose provides energy so to remember: People Have Lots Of Energy = Phloe(m)

What is the transpiration stream?

Water evaporates from leaves through transpiration. As it is lost, the xylem draw up more from the soil so there is a continuous movement of water in and out of the plant

What is osmosis?

The movement of water from a high concentration to a low concentration across a partially permeable membrane

What is peristalsis?

Contraction of the muscles in the esophagus to move the food through the digestive system

What is the gall bladder?

A small sac connected to the small intestine which stores bile used

What do carbohydrases do?

Digest carbohydrates into glucose

What do proteases do?

Digest proteins into amino acids

What do lipases do?

Digest fats and oils into fatty acids and glycerol

What is emulsification?

When bile breaks down fats into small droplets to incr