test 2 Flashcards

1
Q

How are sperm cells specialised for their function?

A

1 - nucleus containing haploid chromosomes
2 - tightly packed mitochondria to provide ATP for movement of tail
3 - flagellum propels sperm
4 - microtubules keep sperm in suspension to move tail
5 - acrosome stores enzymes to digest zona pellucida

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2
Q

Describe the structure of an egg cell

A

1 - follicle cells release chem for acrosome reaction
2 - zona pellucida: glycoprotein for sperm to bind
3 - cortical granules
4 - lipid droplets: food store for embryo

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3
Q

What is the role of the cortical granules?

A

lysosome which releases enzymes to thicken zona pellucida and prevent further entry of sperm

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4
Q

Describe the stages of fertilisation

A

1 - Follicle cell releases chemical which triggers acrosome reaction
2 - Acrosome membrane fuses with front of sperm cell membrane and digestive enzymes released
3 - Enzymes digest zona pellucida
4 - Sperm membrane fuses with ovum membrane & nucleus enters ovum
5 - Cortical reaction: zona pellucida thickens to prevent entry of other sperm
6 - Egg and sperm nuclei fuse - diploid zygote

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5
Q

How does meiosis create genetic variation?

A

Crossing over of chromatids: same genes but different alleles
Independent assortment: different combo of maternal and paternal chromosomes

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6
Q

What is a gene locus?

A

Location of genes on a chromosome

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7
Q

What is gene linkage?

A

Genes with loci on the same chromosome so they aren’t inherited separately

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8
Q

The closer the loci of 2 genes…

A

The more closely they’re linked and less likely to be separated by crossing over

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9
Q

How do cells specialise?

A

Gene activated by stimulus
mRNA transcribed from active gene and translated into proteins
Protein determines structure and function of cell

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10
Q

How do transcription factors control gene expression in eukaryotes?

A

Methylation of DNA prevents transcription by stopping RNA polymerase binding
Histone modification - acetylation makes chromatin less condensed so RNA polymerase can bind

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11
Q

How can gene expression be controlled?

A

Rate of transcription of genes
Transcription factors
Activators & repressors

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12
Q

What is an operon?

A

Section of DNA containing promoter and operator

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13
Q

What happens when lactose is present?

A

Binds to repressor, changing its shape so it can’t bind to the promoter, B galactosidase expressed

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14
Q

What happens when lactose is absent?

A

Lac repressor binds to operator site and stops transcription as RNA polymerase can’t bind to promoter

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15
Q

What is biodiversity?

A

Number of different species and genetic variation within species

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16
Q

Define ecosystem

A

A self-sustaining life-supporting environment with biotic and abiotic factors

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17
Q

What is species evenness?

A

when species have similar abundances, no dominant species

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18
Q

How is genetic variation measured?

A
  1. DNA sequenced to determine bases and alleles
  2. DNA copied using PCR and cut with restriction enzymes
  3. fragments separated by gel electrophoresis to create a banding pattern
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19
Q

What does 2 bands in gel electrophoresis mean?

A

heterozygous as there’s a band for each allele

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20
Q

What is the heterozygosity index?

A

number of heterozygotes / number of individuals in a population

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21
Q

Why is a large heterozygosity index good?

A

more heterozygous a population, the larger the gene pool

increased chance of survival

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22
Q

Why is inbreeding bad?

A

heterozygosity lost, smaller gene pool
decreased chance of survival
recessive alleles have harmful effects (inbreeding depression)

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23
Q

How is maltose formed?

A

2 alpha glucose in condensation

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24
Q

How is sucrose formed?

A

Alpha glucose and alpha fructose (1-2) glycosidic bond

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25
How is lactose formed?
Beta galactose and alpha glucose B(1-4) glycosidic
26
Function of maltose
Respiratory substrate, germinating seeds
27
Function of sucrose
Transporting energy in plants
28
Function of lactose
mammalian milk
29
How is the structure of starch related to its function?
Amylopectin large chain of glucose units: available for respiration Amylose helix coiled: compact, lots of glucose in small space Amylopectin is branched and compact: lots of glucose for resp Large so it's insoluble
30
How is the structure of glycogen related to its function?
Branched: easily hydrolysed do glucose released quickly Compact, stores lots of glucose Large, so it's insoluble
31
Describe the structure of cellulose
Alpha glucose and beta | Unbranched straight chains align parallel to each other forming microfibrils (H bond)
32
What are some natural causes of rising temperatures?
- variations in solar activity - fluctuations in ocean currents - volcanic eruptions
33
How do ice cores help determine temperature?
measurement of O-18 and O-16 | warmer climates have more O-18 because it is preferred in precipitation and evaporates
34
What are the conditions in peat bogs?
acidic, cool, anaerobic
35
Why do anaerobic conditions reduce decompositions?
no oxygen so decomposing bacteria can't respire so die digestive enzymes not present acidic pH reduces enzyme action
36
Why might peat bogs not provide any evidence sometimes?
layers destroyed or mixed
37
Why is pollen in peat bogs useful? (4)
large amounts resistant to decomposition distinct pollen for diff species each species grows best in particular climate
38
How are insect records taken from peat bogs and why are they more useful?
exoskeleton preserved in bogs | populations respond faster to climate change so more accurate
39
Is the spring growth dark or light? Why?
light because it's wet and warm so wider xylem vessels
40
Is summer growth dark or light? Why?
dark because it's warmer and dry so less growth and narrow xylem
41
What is the atmosphere?
a layer of gases surrounding a planet
42
How does the atmosphere sustain life? (3)
contains O2 for respiration, CO2 for PS ozone layer absorbs UV light, reducing genetic damage maintains stable average temp, sustaining life
43
How does the atmosphere maintain a stable temperature?
greenhouse effect
44
Describe the greenhouse effect
1. Short wavelength solar radiation passes through atmosphere 2. Some radiation absorbed, warming the Earth 3. Some longer IR radiation reflected off the Earth's surface 4. Longer wavelength IR absorbed by greenhouse gases, increasing the Earth's temperature
45
Which greenhouse gas has the biggest effect on GHE?
water vapour because it has a high specific heat capacity and can absorb the most heat energy
46
What is global warming potential (GWP)?
a relative measure of how much heat a green house gas traps in the atmosphere
47
What is global warming?
enhanced greenhouse effect due to an increased level of greenhouse gases
48
What does two data sets from different locations confirm?
that the trend is global
49
Why are there CO2 fluctuations?
photosynthesis high in summer and low in winter summer: PS > R winter: R > PS
50
Why are CO2 levels increasing? (2)
increase in fossil fuel in combustion so growing energy demand deforestation (less PS)
51
What are the sources of methane? (4)
anaerobic bacteria in marshes and rice paddies anaerobic bacteria in guts of ruminants decomposition of organic material leakage from gas pipes
52
Why are methane levels increasing? (3)
increase in rice paddy fields due to demand for food increase in ruminant population due to demand for food increase in number of landfill sites
53
What are the sources of nitrous oxide? (2)
combustion of fossil fuels | denitrifying bacteria acting on nitrates
54
Why are nitrous oxide levels increasing? (3)
increase in fossil fuel combustion increased use of nitrate fertilisers increased cultivation of soil
55
Why is climate change science controversial? (5)
``` science cannot prove theories alternative interpretations exist knowledge about climate is incomplete available data has limitations interpretation bias ```
56
What is a scientific theory?
a comprehensive explanation of some aspect of nature that is supported by a vast body of evidence and upon which predictions can be made
57
What are some limitations with data?
Not a long data set Only from 1 country Other factors responsible Validity of experiment - how was it measured?
58
What is extrapolation?
an estimate outside the recorded or observed range
59
What assumptions are made when extrapolating?
- enough data to establish a trend | - present trend continues
60
What factors need to be taken into account to predict CO2 concentration? (5)
- price of fossil fuel - Kyoto protocol - clean technology - amount of PS - increase in population
61
What are climate models?
quantitative methods to simulate the interactions of the different factors to project future climate
62
What are the limitations of climate models? (5)
- limited data - limited knowledge on how climate works - limiting computing resources - not all factors considered - changing factors
63
How are flora and fauna adapting to climate change?
- changes in distribution - changes in development - changes in life cycle
64
How is distribution of species changing? Why?
- species migrating north - loss of habitats and food sources (not ideal conditions) - competition with aliens species and changes in dominant species
65
What happens to rate of reaction when temperature increases?
- increases (doubles for every 10C increase) | - more collisions of substrate and enzyme due to higher KE
66
Why does rate of reaction decrease when temperature is increased too much?
- secondary and tertiary bonds break due to high vibration of molecules - enzyme denatures, active site changes shape, no binding of substrate
67
What happens when rainfall patterns change?
- affects development and life cycles of organisms (plants remain dormant for longer) - affects distribution of species: more desert areas
68
Describe the structure and function of smooth muscle
- non striated - spindle shaped - uninuclear fibres - involuntary - in walls of internal organs
69
Describe the structure and function of cardiac muscle
- striated - branched - uninuclear fibres - involuntary - walls of the heart
70
Describe the structure and function of skeletal muscle
- striated - tubular - multinuclear fibres (cells) - voluntary - attached to skeleton
71
What is a tendon?
joins muscles to bones - white fibrous tissue - bundles of collagen fibres - inelastic
72
What is cartilage?
tissue at the ends of bones, made of chondrocytes and collagen, to prevent bone erosion - elastic - shock absorber
73
How do muscles allow movement?
antagonist pairs which work in opposite directions: - flexor (reduces angle) - extensor (straightening)
74
Describe the structure of a section of skeletal muscle
bundles of muscle fibres with myocytes (single muscle cells)
75
Describe the structure of a myocyte
- multi-nucleate - made up of contractile myofibrils - sarcolemma, sarcoplasm, sarcoplasmic reticulum - sarcosomes (mitochondria) for ATP
76
What are myofibrils?
bundles of myofilaments, which are repeated chains of sarcomeres
77
What are A bands?
dark bands contain thick myosin and overlapping thin actin
78
What are I bands?
light bands containing only thin actin filaments
79
What is the Z line?
sarcomeres are joined here
80
What is the M line?
middle of the myosin filaments
81
What does the H zone contain?
only thick myosin filaments
82
What happens to the I band in contraction?
gets shorter
83
What happens to the A band in muscle contraction?
stays the same
84
What happens to the H zone in contraction?
gets shorter
85
What happens when muscles are relaxed?
- no Ca2+ so tropomyosin blocks the myosin binding site on actin - myofilaments can't slide past each other as heads can't bind
86
How is muscle contraction triggered?
- nerve impulse reaches axon terminals at neuromuscular junction - depolarises sarcolemma and spreads to sarcoplasm - neurotransmitter released and binds to receptors on muscle cells - Ca2+ released from sarcoplasmic reticulum
87
How do muscles contract?
1 - Ca2+ binds to troponin and pulls tropomyosin away from binding site 2 - Myosin head (ADP + Pi) attaches to actin, forming cross bridge 3 - Pi released, causing power stroke: myosin pulls on actin 4 - ADP released 5 - ATP binds to myosin head and cross-bridge detaches 6 - Myosin ATPase hydrolyses ATP to ADP + Pi so it has energy
88
What is sex linkage?
Genes that are on the sex chromosome and inherited with the sex chromosome