B3a - molecules of life Flashcards

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1
Q

Why do liver and muscle cells have large numbers of mitochondria?(4)

A

Number of mitochondria in the cytoplasm depends on the activity of the cell, since respiration occurs in the mitochondria

Liver and muscle cells need a lot of energy so they need a large number of mitochondria

  • Liver cells carry out energy demanding reactions
  • Muscle cells need energy to contract
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2
Q

Describe ribosomes(3)

A

Some structures in a cell are too small to be seen with a light microscope - e.g. ribosomes

Also found in the cytoplasm

Site of protein synthesis

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3
Q

Describe the structure of DNA(3)

A

Two strands coiled to form a double helix

Each strand containing chemicals called bases, of which there are four different types

Cross links between the strands formed by pairs of bases.

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4
Q

Describe chromosomes(2)

A

Long, coiled molecules of DNA

Divided up into regions called genes.

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5
Q

Describe genes(3)

A

A section of chromosome made of DNA

Each gene contains a different sequence of bases

Each gene codes for a particular protein

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6
Q

What are the 4 bases

A

A,T,C,G

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7
Q

Describe complementary base pairing(2)

A

A pairs with T

G pairs with C

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8
Q

How is protein structure determined by the DNA base code(2)

A

The base sequence determines amino acid sequence

Each amino acid is coded for by a sequence of 3 bases.

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9
Q

Why is a copy of a gene needed to make proteins(4)

A

Proteins are made in the cytoplasm by ribosomes

Genes cannot leave the nucleus as they are too big to fit through the gap

A copy of a gene is used which can leave the nucleus and carry the code needed to make the protein to the cytoplasm
-done by mRNA, which carries the code from the DNA to the ribosomes

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10
Q

How does DNA control cell functions

A

By controlling the production of proteins, some of which are enzymes

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11
Q

What data did Watson and Crick use from other

scientists to build a model of DNA(2)

A

X-ray data showing that there were two chains wound in a helix

Data indicating that the bases occurred in pairs

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12
Q

Why are new discoveries, such as Watson and

Crick’s, not accepted or rewarded immediately

A

Other scientists need to repeat and test the work to make sure it is correct

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