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biology a level ocr snab > topic 3 - voice of the genome > Flashcards

topic 3 - voice of the genome Flashcards

1
Q

what are prokaryotic cells?

A

bacteria and cyanobacteria

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2
Q

are prokaryotic or eukaryotic cells larger?

A

eukaryotic
eukaryotic cells are 20um in diameter, whereas prokaryotic cells are only 0.5 to 5um

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3
Q

where is the dna stored in prokaryotic cells?

A

it lies free in the cytoplasm, in large circles of dna or plasmids

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4
Q

what is the difference between prokaryotic and eukaryotic cells?

A
  • prokaryotic cells have no membrane-bound organelles
  • eukaryotic cells are larger
  • prokaryotic cells have no nucleus
  • all prokaryotic cells have cell walls whereas only some eukaryotic cells do
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5
Q

what is the function of the pili?

A

allows bacteria to stick to surfaces

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6
Q

what is the function of the flagellum?

A

rotates to allow the cell to move

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7
Q

what is the function of the capsule?

A

protects the cell and prevents dehydration of the cell

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8
Q

what is the function of the mitochondria?

A

the site of the later stages of aerobic respiration

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9
Q

what is the function of the nucleus?

A

contains chromosomes made of dna and a nucleolus

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10
Q

what is the function of the nucleolus?

A

where the ribosomes are made

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11
Q

what is the function of the rough endoplasmic reticulum?

A

ribosomes are attached to the outer surface, and proteins made on these ribosomes are transported through the ER to other parts of the cell

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12
Q

what is the function of the ribosomes?

A

made of rna and protein, the site of protein synthesis

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13
Q

what is the structure and function of the cell surface membrane?

A

phospholipid bilayer forming a partially permeable membrane

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14
Q

what is the function of the smooth endoplasmic reticulum?

A

makes lipids and steroids

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15
Q

what is the structure and function of the golgi apparatus?

A

formed by the fusion of vesicles from the ER, modifies proteins and packages them for transport

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16
Q

what is the function of the lysosome?

A

spherical sacs containing digestive enzymes, involved in the breakdown of unwanted structures within the cell, and the destruction of whole cells

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17
Q

what is the structure and function of the centrioles?

A

involved in the formation of the spindle during nuclear division and in transport within the cell cytoplasm. hollow cylinders made up of a ring of protein microtubules

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18
Q

how do ovum (egg) cells move towards the uterus?

A

wafted along the oviducts by ciliated cells lining the tubes, and muscular contractions

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19
Q

what is the structure of the egg cell/ovum?

A

cytoplasm contains protein and lipid food reserves for a developing embryo. surrounded by the zona pellucida which is a jelly-like coating

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20
Q

how does the sperm cell move?

A

the flagellum is powered by energy released by the mitochondria

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21
Q

how does the sperm know where to swim?

A

the ovum releases chemicals which attracts the sperm cells

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22
Q

what is the structure of a sperm cell?

A

acrosome at the head to break down the zone pellucida and flagellum to help it swim

23
Q

what is the acrosome reaction?

A

the acrosome fuses with the cell surface membrane and releases digestive enzymes which break down the zone pellucida

24
Q

what is the acrosome?

A

a type of lysosome (enzyme-filled sacs)

25
Q

what is the cortical reaction?

A

after one sperm cell has penetrated the egg, the ovum releases chemicals to thicken the zona pellucida, preventing any further sperm from entering the egg

26
Q

how do gametes form?

A

meiosis

27
Q

how does meiosis result in genetic variation?

A

independent assortment and crossing over

28
Q

what is independent assortment?

A

as only one chromosome from each pair ends up in each gamete during meiosis, it is random how they are split up and there are many possible combinations

29
Q

what is crossing over?

A

during meiosis 1, all four chromatids come into contact, and at contact points, the chromatids break and rejoin, exchanging sections of dna

30
Q

what is the site of crossing over called?

A

chiasma/chiasmata plural

31
Q

how can some genes be ‘linked’ and be more likely to be inherited together?

A

the closer together they are on the same chromosome, the less likely they are to be split during crossing over, meaning they are more likely to be inherited together

32
Q

how can a gene be sex-linked?

A

if a gene loci is on the x chromosome, men have a higher chance of developing recessive conditions as they only need one copy of that gene, whereas women would need one copy on each chromosome, which is less likely

33
Q

what is a fertilised ovum called?

A

a zygote

34
Q

what are the common features of a eukaryotic cell?

A
  • genetic material contained in nucleus
  • genetic material in chromosomes
  • membrane-bound organelles
  • larger ribosomes (80s) than prokaryotes (70s)
  • sometimes have cell walls - made of cellulose where present
35
Q

what are the common features of a prokaryotic cell?

A
  • no nucleus
  • no membrane-bound organelles
  • mesosomes instead of mitochondria for respiration
  • circular dna
  • all have cell walls
36
Q

how is the cell cycle divided?

A

two distinct parts - interphase and division

37
Q

starting with mitosis, what are the stages of the cell cycle in order?

A

mitosis, cytoplasmic division, g1, s, g2

38
Q

what is interphase?

A

the stage of the cell cycle where the cell synthesises new cell components, such as new organelles, membranes, and dna. by the end, the cell contains enough to produce two new cells

39
Q

what is synthesised during each stage of interphase?

A

new cellular proteins form throughout interphase, dna synthesises during s phase

40
Q

why is the embryonic cell cycle faster than other body cells?

A

the zygote already contains the materials needed to form the first few cells so there is no interphase for the first few divisions

41
Q

describe the organisation of dna in chromosomes

A

the dna double helix winds around histone proteins to form a chain. this chain coils to form a chromatin fibre, which attaches to a protein scaffold, forming loops. folding the protein scaffolding produces a chromosome

42
Q

what happens to chromosomes during interphase?

A

the individual chromosomes are unravelled, allowing access to the genetic material so new proteins can be synthesised

43
Q

what are the stages of mitosis?

A

prophase, metaphase, anaphase, and telophase

44
Q

what is prophase?

A

the stage of mitosis where the chromosomes condense, with each chromosome visible as two strands/chromatids joined at the centromere. microtubules form spindle. centrioles move around to position themselves at opposite sides of the cell, to form the two poles and spindle fibres form between these poles. the nuclear envelope breaks down to signal the end

45
Q

what is metaphase?

A

the chromosomes’ centromeres attach to spindle fibres at the equator

46
Q

what is anaphase?

A

the centromeres split, and the spindle fibres shorten to pull the two halves in opposite directions. anaphase ends when the separated chromatids each the poles and the spindle breaks down

47
Q

what is telophase?

A

the last stage of miotic division. the chromosomes unravel, the nuclear envelope reforms, and the two sets of genetic information become enclosed in separate nuclei

48
Q

what is cytoplasmic division?

A

the final reorganisation into two new cells. in animal cells, the cell surface membrane constricts around the centre. in plant cells, a new cell plate is synthesised

49
Q

why is mitosis so important?

A
  • ensures genetic consistency as daughter cells are genetically identical
  • growth and repair
50
Q

what is a totipotent cell?

A

has the ability to develop into a complete human being

51
Q

what is the blastocyst?

A

a hollow ball of cells formed 5 days after contraception. outer layer forms the placenta. inner cells are pluripotent embryonic stem cells

52
Q

what is a pluripotent cell?

A

has the ability to develop into most cell types

53
Q

what it a multipoint cell?

A

have the ability to develop into a variety of cell types. e.g neural stem cells cam give rise to various types of cells found in the nervous system

54
Q

how is the differentiation of cells different in plants compared to animals?

A

plant cells can de-differentiate and many remain totipotent throughout the whole life of the plant

biology a level ocr snab (3 decks)

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