B3

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What does a plant cell have that an animal cell doesn't?
It has chloroplasts, cell wall and a vacuole.
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What does the chloroplast contain and what does it do?
It contains a green pigment called chlorophyll which traps light energy from the sun and uses it for photosynthesis.
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What does a bacterial cell have instead of a 'true' nucleus?
They have a single circular strand of DNA that floats freely in the cytoplasm.
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Describe briefly what a DNA molecule looks like?
It is a double helix and is made up of lots of small groups called nucleotides. Each nucleotide contains one of the four possible bases. These bases form cross links to the complementary base on the other strand.
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Who were the first people to build a model of DNA in 1953?
Francis Crick and James Watson.
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How does DNA replicate itself?
First the molecule of DNA unzips itself, then free-floating nucleotide pair up with complementary bases on the DNA. Finally, cross links form between the bases and the old DNA strands, and the nucleotides are joined together to form double strands.
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Describe the process of protein synthesis.
The order of the bases in a gene decides the order of amino acids in a protein; each amino acid is coded for by a sequence of three bases in a gene. The amino acid is joined together to make a protein (unique protein=different sequence of bases).
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What is the job of the mRNA and why is it important?
mRNA carries the DNA code from the nucleus to the ribosome where it is used to code for proteins. It is important because DNA is too big to move out of the nucleus and to the ribosome.
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How do some cells only make a certain type of protein?
Because they only use some of the full set of genes only certain proteins are made: some genes are "switched off".
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What are the 4 different types of proteins?
Enzymes, Carrier Molecules, Hormones and Structural Proteins.
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Why are enzymes also referred to as biological catalysts?
Because they speed up chemical reactions inside the body without being used up.
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What is the substrate?
It is the molecule changed in the reaction.
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What is the active site and what does it have to do with the substrate?
It is the part of the enzyme which joins on to the substrate to catalyse the reaction.
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What is the optimum temperature of most enzymes?
About 37 degrees Celsius.
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Why does the rate of reaction start to decrease after the optimum temperature?
Because some of the bonds holding the enzyme will break and so the enzyme will denature: therefore it will not be able to catalyse the reaction.
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What happens to enzymes if the pH is too high?
They will denature and will not be able to catalyse the reaction.
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What is the Q10 value?
It shows how much the rate of reaction changes when the temperature is raised by 10 degrees Celsius.
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How do you calculate the Q10 value?
Rate at higher temperature/ Rate at lower temperature (rate at 40/rate at 30).
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What is a mutation?
It is a change in the DNA base sequence.
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Why are mutations potentially dangerous?
If a mutation occurs within a gene, it could stop the production of the protein that the gene usually codes for: or a different protein could be produced instead.
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Give examples of where mutations are harmful.
If the mutation causes the gene to not be able to code an important protein (enzyme), if the mutation occurs in the reproductive cells the offspring could die or could develop abnormally it could cause cancer. One example is down syndrome.
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Give examples of where mutations could be beneficial.
The mutation could cause the gene to code for a protein which is better than the previous protein (survival advantage). One example is sickle cell anaemia which makes the person resistant to malaria.
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What are the advantages of being multicellular?
You can be bigger (less predators, can travel further,etc), allows for cell differentiation and you can be more complex (adapted to a certain environment).
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What 3 systems do multicellular organisms need to have?
A system to communicate between different cells (nervous system), a system to provide cells with the nutrients they need (circulatory system) and a system that controls the exchange of substances with the environment (respiratory system).
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What is mitosis?
When a cell reproduces itself by splitting to form two identical offspring.
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What is meiosis and what are formed by this process?
Meiosis is a different type of cell division that produces 4 new cells. Gametes are formed by meiosis.
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What is the difference between haploid and diploid?
A haploid cell is a cell that only has one copy of each chromosome; whereas a diploid cell is when the cell has 2 copies of each chromosome in its nucleus.
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How are sperm adapted to their function?
They are small and have a long tail so that can swim to the egg, have lots of mitochondria (provides them with energy to get to the egg) and they have an acrosome at the tip of their head (releases enzymes to digest through egg's membrane).
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What is the difference between animal and plant growth?
Animals grow until they reach a certain size but plants continue to grow throughout their life. Also, in animals growth happens because of cell division; however in plants most of the growth happens due to cell elongation.
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What are stem cells?
They are undifferentiated cells which can develop into any types of
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Where are stem cells found and how are they beneficial to us?
Stem cells are found in early human embryos and they are used to cure many
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What does the chloroplast contain and what does it do?

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It contains a green pigment called chlorophyll which traps light energy from the sun and uses it for photosynthesis.

Card 3

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What does a bacterial cell have instead of a 'true' nucleus?

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Preview of the front of card 3

Card 4

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Describe briefly what a DNA molecule looks like?

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Card 5

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Who were the first people to build a model of DNA in 1953?

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