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GCSE Biology Edexcel (Additional) > Topic 1- The Building Blocks of Cells > Flashcards

Topic 1- The Building Blocks of Cells Flashcards

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1
Q

What did the first light microscopes allow scientists to see?

A

small, single-celled organisms and the cells that made up larger life

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2
Q

How do light microscopes work?

A

they use glass lenses to refract light and produce a magnified image

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3
Q

What is the calculation for the magnification of a light microscope?

A

multiply the magnification of the eye piece lens by the objective lens

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4
Q

How do electron microscopes work?

A

instead of using light, they shine a beam of electrons through a sample

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5
Q

What is the difference between the wavelength of electrons and the wavelength of light?

A

the wavelength of electrons is much smaller than the wavelength of light

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6
Q

Why might a scientist choose to use an electron microscope rather than a light microscope?

A

the wavelength of electrons is much smaller than the wavelength of light, and this means that a much greater magnification and detail can be seen

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7
Q

What are the 4 main features of an animal cell?

A

1- nucleus
2- cytoplasm,
3- cell membrane
4- mitochondria

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8
Q

What are the 7 main features of a plant cell?

A 
1- nucleus
2- cytoplasm
3- cell membrane
4- mitochondria
5- cellulose cell wall
6- large vacuole (almost always)
7- chloroplasts (those that are exposed to light)
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9
Q

What are the 5 main features of a bacterial cell?

A 
1- cytoplasm
2- cell wall (non-cellulose)
3- plasmid DNA
4- chromosomal DNA
5- Flagella
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10
Q

How many pairs of chromosomes are in normal human cells?

A

23 pairs

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11
Q

What do chromosomes consist of?

A

long, coiled molecules of DNA

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12
Q

what does DNA stand for?

A

deoxyribonucleic acid

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13
Q

What is a gene?

A

a section of DNA which codes for a particular protein

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14
Q

What does a DNA molecule consist of?

A

Two strands, which are coiled to form a ‘double helix’. The strands are linked by a series of paired ‘complementary bases’.

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15
Q

What are the names of the 4 complementary bases in DNA?

A

adenine (A), cytosine (C), guanine (G), and thymine (T)

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16
Q

What does adenine link to (and vice versa)?

A

adenine only ever links to thymine (A-T)

17
Q

What does cytosine link to (and vice versa)?

A

cytosine only ever links to guanine (C-G)

18
Q

What are the complementary bases held together by?

A

weak hydrogen bonds

19
Q

(H) Who was Fred Sanger?

A

A biochemist, who, in 1977, discovered a way of identifying the sequence of bases in DNA.

20
Q

(H) What is a genome?

A

A genome is all of the genetic material in an organism

21
Q

(H) What were the aims of The Human Genome Project?

A
  • to work out the order or sequence of all the three billion base pairs in the human genome
  • to identify all the genes
  • to develop faster methods for sequencing DNA
22
Q

(H) Why might knowing where a gene appears on a chromosome and how it is made up, be useful for doctors?

A

doctors could identify and replace ‘faulty’ genes which cause genetic disorders

23
Q

(H) Why might knowing where a gene appears on a chromosome and how it is made up, be useful for forensic scientists?

A

forensic scientists could use the information to compare DNA samples from potential suspects with those found at a crime scene, and therefore convict or clear them of the crime

24
Q

Who were the four scientists involved in the discovery of the structure of DNA?

A

James Watson, Francis Crick, Rosalind Franklin and Maurice Wilkins

25
Q

Who discovered the double helix model of DNA?

A

James Watson and Francis Crick, in 1953

26
Q

How did Franklin and Wilkins investigate the structure of DNA?

A

they took an X-ray diffraction image of DNA

27
Q

What is the basis of genetic engineering?

A

it involves removing a gene from one organism and inserting it into another

28
Q

If genes from one species are inserted into animals of a different species, what are they called?

A

‘transgenic’ animals

29
Q

Transgenic cows have been created to produce ‘designer milk’. What does this milk contain?

A
  • extra protein (casein)
  • low levels of cholesterol
  • human antibodies (normally produced by our white blood cells)
30
Q

How has rice been genetically modified to benefit humans?

A

rice has been genetically modified to contain a beta-carotene gene to reduce Vitamin A deficiency in humans. Vitamin A deficiency can lead to blindness in children.

31
Q

How can genetic modification benefit diabetics?

A

the human gene for insulin has been inserted into bacteria, which are then used to produce insulin on a larger scale to treat diabetics

32
Q

What are herbicides used for?

A

to kill weeds, which prevent crop plants from growing

GCSE Biology Edexcel (Additional) (3 decks)

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