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Topic 3 completed Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

what are the 12 organelles found in an animal cell?

A

rough endoplasmic reticulum, smooth endoplasmic reticulum, Golgi apparatus, ribosomes, nucleus, nucleolus, centriole, plasma membrane, lysosome, nuclear envelope, cytoplasm, mitochondrion

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2
Q

what type of cell are animal cells?

A

eukaryotic

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3
Q

describe the nucleus

A

large organelle surrounded with nuclear envelope (double membrane), contains chromatin and the nucleolus

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4
Q

what is the function of the nucleus?

A

controls cells activities by controlling transcription, nucleolus makes ribosomes

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5
Q

describe the lysosome

A

round organelle, surrounded with a membrane, has no clear internal structure

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6
Q

what is the function of a lysosome?

A

contains digestive enzymes, used to digest invading cells or break down worn out components of the cell

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7
Q

describe a ribosome

A

small organelle, can float free or be attached to RER, made up of proteins and RNA, no membrane

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8
Q

what is the function of a ribosome?

A

site of translation (where proteins are made)

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9
Q

describe a rough endoplasmic reticulum

A

system of membranes enclosing a fluid- filled space, surface covered with ribosomes

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10
Q

what is the function the rough endoplasmic reticulum?

A

folds and processes proteins which have been made at the ribosomes

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11
Q

describe the smooth endoplasmic reticulum

A

a system of fluid filled membranes enclosing a fluid filled space

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12
Q

what is the function of the smooth endoplasmic reticulum?

A

synthesises and processes lipids

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13
Q

describe the golgi apparatus

A

a group of fluid filled, membrane bound, flattened sacs, vesicles seen at edges

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14
Q

what is the function of the golgi apparatus?

A

processes and packages new lipids and proteins, and makes lysosomes

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15
Q

describe the mitochondrion

A

oval shaped, double membrane, inner membrane folds into the matrix to form cristae, matrix contains enzymes for respiration

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16
Q

what is the function of a mitochondria?

A

site of aerobic respiration, where ATP is produced, large numbers are found in very active cells that require lots of energy

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17
Q

describe a centriole

A

small, hollow structures, made of microtubules, found in animal and some plant cells

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18
Q

what is the function of a centriole?

A

involved with separation of chromosomes during cell division

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19
Q

what is the secretory pathway?

A

proteins made at a ribosome
proteins produced at rough ER are folded and processed (e.g. sugar chains added) in the rough ER
transported from the ER to the Golgi apparatus in vesicles
Golgi processes protein
protein enters another vesicle to be transported around the cell or to the cell membrane (exocytosis)

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20
Q

If a protein is made on a ribosome on the RER, where does it go?

A

out of the cell or into cell membrane

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21
Q

If a protein is made on a free ribosome, where does it go?

A

it stays in the cytoplasm

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22
Q

what are the 9 features of a prokaryotic cell?

A

70s ribosomes, flagella, circular DNA, plasmids, mesosomes, cell walls (peptidoglycan for bacteria), slime capsule, pili, plasma membrane

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23
Q

does the cytoplasm of a prokaryote have membrane bound organelles?

A

no

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24
Q

what is the function of flagella?

A

rotate to make the cell move
some cells have multiple and some will have none

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25
Q

describe the DNA in a prokaryotic cell

A

free floating circular DNA (one long coiled-up strand) not attached to any histone proteins

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26
Q

what are plasmids?

A

small, circular loops of DNA which contain genes for things such as antibiotic resistance and can be passed easily between prokaryotes

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27
Q

what are mesosomes?

A

inward folds of plasma membrane- unsure of function but may have a role in cellular processes such as respiration

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28
Q

what is the function of a slime capsule?

A

helps to protect bacteria from immune system cells

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29
Q

what are pili?

A

short hair-like structures which help stick prokaryotes to other cells and used in gene transfer between cells

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30
Q

what is the cell membrane in a prokaryotic cell made of?

A

lipids and proteins just like a eukaryotic cell

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31
Q

what are the advantages of light microscopes?

A

uses light so sample can be living
cheaper
smaller

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32
Q

what are the advantages of an electron microscope?

A

higher resolution- gives a more detailed image
high max magnification- can see small organelles such as lysosomes

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33
Q

what are the 2 types of electron microscope?

A

transmission electron microscope- denser parts absorb more electrons and look darker, give high resolution images, thin samples only
scanning electron microscope- can give 3D images, thick specimens, lower resolution

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34
Q

define a tissue

A

a group of similar cells that are specially adapted to work together to carry out a particular function

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35
Q

give an example of a plant tissue

A

xylem tissue

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36
Q

define organ

A

a group of different tissues that work together to perform a particular function

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37
Q

give an example of a plant organ

A

the leaf

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38
Q

what are the layers in a leaf cross section?

A

waxy cuticle
upper epidermis
palisade mesophyll
spongy mesophyll
lower epidermis

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39
Q

what does mitosis produce?

A

2 genetically identical diploid daughter cells needed for growth, repair and asexual reproduction

40
Q

what are the stages of the cell cycle?

A

interphase and mitosis

41
Q

what are the stages of interphase?

A

gap phase 1, synthesis, gap phase 2

42
Q

what happens in gap phase 1?

A

cell grows and new organelles and proteins made

43
Q

what happens in synthesis?

A

cell replicates its DNA, ready to divide by mitosis

44
Q

what happens in gap phase 2?

A

cell keeps growing and proteins needed for cell division are made

45
Q

what are the stages of mitosis?

A

prophase, metaphase, anaphase, telophase

46
Q

what happens during prophase?

A

chromosomes condense, centrioles move to poles of cell and form a network of spindle fibres, nuclear envelope breaks down

47
Q

what happens in metaphase?

A

chromosomes line up along middle of cell and spindle fibres attach to their centromere

48
Q

what happens during anaphase?

A

centromeres divide- separating sister chromatids, spindle fibres contract pull chromatids to poles centromere first (V-shape)

49
Q

what would happen if the centromeres couldn’t shorten?

A

chromatids cannot be separated, anaphase cannot occur, mitosis will not be completed

50
Q

what happens during telophase?

A

chromatids uncoil in poles, now called chromosomes, nuclear envelopes form around the 2 groups, cytoplasm divides (cytokinesis)

51
Q

why is HCl used in the mitosis core practical?

A

to break down middle lamella, to allow cells to be separated, to allow light to pass through

52
Q

how many chromosomes does a human gamete have?

A

23

53
Q

how is an egg cell adapted for its function?

A

zona pellucida- protective glycoprotein layer that sperm have to penetrate, hardens once they have entered, prevents polyspermy
haploid nucleus- zygote has correct 46 chromosomes
follicle cells- protective layer
cortical granules- release substances which cause the zona pellucida to harden

54
Q

how is a sperm cell adapted for its function?

A

mid piece contains may mitochondria to provide flagellum lots of energy to rotate and move the cell
acrosome contains digestive enzymes which breakdown the zona pellucida and allow the sperm to fertilise the cell

55
Q

what are the stages of fertilisation?

A

sperm makes contact with the zona pellucida and the acrosome reaction occurs (digestive enzymes break down the zina pellucida)
sperm head fuses with the cell membrane which triggers the cortical reaction (egg cell releases cortical granules from vesicles into the space between the cell membrane and the zona pellucida)
the cortical granules cause the zona pellucida to thicken and prevent polyspermy
the sperm nucleus enters the cell and fuses with the nucleus of the egg cell

56
Q

what does meiosis produce?

A

4 genetically different haploid daughter cells

57
Q

what are the stages of meiosis?

A

1- DNA replicates so there’s 2 identical copies of each chromosome
2- DNA condenses into double armed chromosomes
3- chromosomes arrange into homologous pairs
4- first division homologous pairs separated, halving chromosome number
5- second division sister chromatids separated

58
Q

what 2 processes make gametes genetically different?

A

crossing over of chromatids and independent assortment of chromosomes

59
Q

how does crossing over of chromatids create genetic variation?

A

before the first division the homologous pairs pair up
two of the chromatids in each homologous pair twist around each other
the twisted bits break off their original chromatid and rejoin onto the other, recombining their genetic material
the chromatids have the same genes but a different combination of alleles

60
Q

how does independent assortment create genetic variation?

A

half the chromosomes in each cell are from the mum and half from the dad
when the gametes are produced different combinations of maternal and paternal chromosomes go into each cell

61
Q

what is meant by the term linked in genetics?

A

genes with loci on the same chromosomes are linked because they are more likely to stay together during independent assortment and their alleles will be passed onto offspring together
genes with loci closer together are linked as crossing over is less likely to split them up

62
Q

when is a characteristic sex-linked?

A

when the locus of the allele that codes for the characteristic is on a sex chromosome

63
Q

why are most genes on the X chromosomes only found on the x and not the Y as well?

A

the X chromosome is much bigger (the Y chromosome doesn’t have enough room)

64
Q

why are males more likely than females to shown recessive genotypes for genes that are sex-linked?

A

males only have one X chromosome and so only have one allele for sex linked genes. So they will show the characteristic whether it’s recessive or dominant

65
Q

define totipotency

A

the ability to produce all cell types

66
Q

define pluripotency

A

the ability of a stem cell to produce all the specialised cells in an organism but not extraembryonic cells

67
Q

how do stem cells become specialised?

A

stem cells all contain the same genes but not all are active (and expressed)
under different conditions, some genes are activated and some are inactivated
mRNA is only transcribed from active genes
the mRNA is then translated into proteins
the proteins modify the cell
changes caused by the proteins make the cell specialised and the changes are difficult to reverse so a cell has to stay specialised

68
Q

what are transcription factors?

A

proteins that bind to DNA and activate or deactivate genes by increasing or deceasing the rate of transcription

69
Q

what are the 2 types of transcription factors?

A

activators- increase the rate of transcription by helping RNA polymerase bind to the DNA and bein transcription
repressors- decrease the rate of transcription by preventing RNA polymerase from binding and so stopping transcription

70
Q

how does gene expression differ between eukaryotes and prokaryotes?

A

in eukaryotes transcription factors bind to specific DNA sites near the start of their target genes
in prokaryotes transcription factors bind to operons

71
Q

what is an operon?

A

a section of DNA that contains a cluster of structural genes, that are transcribed together as well as control elements and sometimes a regulatory gene

72
Q

what do structural genes code for?

A

useful proteins such as an enzyme

73
Q

what are the 2 types of control element in an operon and what do they do?

A

promotor- a DNA sequence located before the structural genes, where RNA polymerase binds to
operator- a DNA sequence that transcription factors bind to

74
Q

what do regulatory genes code for?

A

an activator or repressor

75
Q

what happens at the lac operon in E.coli when lactose is not present?

A

the regulatory gene (lacI) is transcribed to produce lac repressor protein
repressor protein binds to operator
this blocks RNA polymerase from transcribing the rest of the operon as RNA polymerase cannot bind the the promotor
so no enzyme is produced

76
Q

what happens at the lac operon in E.coli when lactose is present?

A

the regulatory gene (lacI) is transcribed to produce lac repressor protein
lactose binds to the repressor protein and changes its shape, this prevents the repressor protein binding to the operator site
RNA polymerase binds to promotor region and transcribes structural genes to produce B-galactosidase

77
Q

how are/will stem cells be used in medicine?

A

leukaemia- bone marrow transplants mean damaged/dead stem cells can be replaced
spinal cord injuries- stem cells could be used to repair damaged nerve tissue
heart disease- stem cells could be used to replace damaged heart tissue

78
Q

what are the 2 types of human stem cells?

A

adult and embryonic

79
Q

describe adult stem cells

A

found in bone marrow
obtained by inserting a needle into the centre on a bone- low risk but painful
aren’t as flexible as embryonic as can only develop into a limited range of cells
less risk of rejection if using stem cells from the same person (different area)

80
Q

describe embryonic stem cells

A

obtained from early embryos 4-5 days old
embryos created in a lab using IVF
the rest of the embryo is destroyed
can develop into all types of cell

81
Q

what are the ethical issues of embryonic stem cells?

A

mean destruction of a viable embryo
some people believe right to life starts at fertilisation

82
Q

regulatory bodies have been stablished for embryonic stem cell research, what do they do?

A

look at proposals of research to make sure the embryos are being used for a good reason and make sure research isn’t unnecessarily repeated
licensing and monitoring centres- to ensure only fully trained staff have access to the embryos

83
Q

what is continuous variation?

A

when the individuals in a population vary within a range- there are no distinct categories

84
Q

give 3 examples of continuous variation

A

mass, height, skin colour

85
Q

what is discontinuous variation?

A

where there are two or more distinct categories and each individual falls into one category

86
Q

give an example of discontinuous variation

A

blood group

87
Q

what is monogenic?

A

when a characteristic is controlled by one gene- usually show discontinuous variation

88
Q

what is polygenic?

A

when a characteristic is controlled by a number of genes at different loci- usually show continuous variation and is more common

89
Q

what is variation in phenotype influenced by?

A

genotype and the environment

90
Q

give 4 ways in which the environment affects the phenotype

A

nutrition- can increase height
Monoamine Oxidase (MAOA)- enzyme which breaks down monoamines, low MAOA levels are linked to mental health issues, levels can be reduced by smoking
diet- can increase the risk of some cancers
temperature- changes in temperature lead to some artic animals having darker hair in the summer and lighter hair in the winter

91
Q

what is epigenetic control?

A

controls which genes are expressed by adding or removing chemical groups from the DNA - altering the phenotype

92
Q

what is methylation?

A

adds a methyl group to the DNA
always added to a CpG site (where cytosine and guanine are next to each other in the DNA)
increased methylation prevents enzymes binding to the DNA and so prevents transcription- gene is repressed/inactivated

93
Q

what are histones?

A

proteins which DNA wrap around to form chromatin (which makes up chromosomes) if the chromatin is highly condensed the enzymes cannot bind and transcription does not occur

94
Q

what is acetylation?

A

when the histones are acetylated the chromatin is less condensed, enzymes can bind, transcription occurs, genes are activated
when the acetyl groups are removed the chromatin becomes highly condensed, enzymes cannot bind, transcription doesn’t occur, gene repressed/ inactivated

95
Q

can epigenetic changes be passed on through cell division?

A

sometimes it can be- this would mean the certain genes are activated or deactivated and the daughter cell will be equipped to deal with the changed environment in the same ay as the original cell

Biology (9 decks)

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