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Name __Casey Hindon____

OCR Gateway GCSE Additional Science

B3: Living and growing

Molecules of life


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DNA code

DNA is a chemical found inside the nucleus. It forms structures called chromosomes. A
section of a chromosome is called a gene. Each gene is a code for making proteins. Our
bodies need to make proteins to grow and repair cells.

Everyone has his or her own unique…

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DNA consists of two long molecules called polynucleotides wrapped around each other.

Each polynucleotide strand is made up of small molecules joined together called bases.

Each nucleotide has a `sticky' part to it called a nucleotide base.
Bases of two different nucleotides can bond to each other and this is…

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Question: Suggest one reason why muscle cells have a lot of mitochondria.
Muscle cells have a lot of mitochondria so plenty of respiration can take place can
take place providing the cell with plenty of energy.
Question: From where does the body get its supply of amino acids?
Either from…

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When DNA replicates, the two polynucleotide strands unwrap. This exposes strands of
the nucleotides.

Floating about in the nucleus are free nucleotides. The bases of these free floating
nucleotides bonds to the exposed bases on the two strands.

Complementary bases pairing occurs, guanine bonds to cytosine and adenine bonds to…

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Question: Write down the complementary base sequence for the section of DNA shown in
the previous question.

Making cheese

When making cheese from milk.

First milk is allowed to turn sour using an enzyme called rennin. Rennin is an
The milk separates into a solid called `curd' and…

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Stage 2: label this stage on your graph

Stage 3: label this on your graph after completing the text below.

As temperature continues to increase, the speed of movement of the substrate and enzyme
molecules also continues to increase. However, the enzyme molecule is also vibrating more
and more energetically.…

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If he has a very high temperature, it is a sign of an infection which could be passed on
to other people.
(b) How would a protease remove a bloodstain on clothes?
Protease is an enzyme which digests proteins and since blood is mainly made out of
proteins, the stain…

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Question: Colour the above diagram as follows:
(a) enzyme = green (b) substrate = blue (c) product = red

It can be seen from the diagram that the enzyme is unchanged after it produces product
molecule/s. The rate of an enzyme controlled reaction is dependent on the rate at which…

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At high temperatures, the enzyme may become denatured and will not work.

Question: Pepsin is an enzyme found in the stomach. It breaks down proteins into amino
acids. Draw a diagram to explain why pepsin cannot break down starch.


Moving substances in the body

To stay alive the body…


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