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Biology > Res 2 flashcards > Flashcards

Res 2 flashcards

1
Q

What is osmosis

A

the net movement of water from an area of high water potential to lower water potential through a semi-permeable membrane, until equilibrium

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2
Q

what is water potential

A

the concentration of water

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3
Q

what is the highest water potential

A

0

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4
Q

what happens when there is more solute in water

A

water potential decreases

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5
Q

describe the characteristics of osmosis

A

passive process- no ATP required
continues until equilibrium
follows movement of solute as water potential decreases
therefore random movement of particles

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6
Q

what happens when animal cell has low water potential and outside has high water potential

A

water enters the cell plasma membrane can’t stretch so cell bursts/cytolyses

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7
Q

what happens when plant cell has lower water potential and outside has higher water potential

A

water enters the cell plasma membrane is surrounded by cell wall therefore the cell becomes turgid

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8
Q

what happens when there is a higher water potential inside animal cell

A

water leaves the cell so cell shrives

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9
Q

what happens when theres a higher water potential in plant cell

A

water leaves and cell becomes plasmolysed

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10
Q

what is plasmolysis

A

when plasma membrane comes away from cell wall

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11
Q

when is something flaccid

A

when all cells in a tissue are plasmolysed

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12
Q

What is the semi-conservative model for DNA replication

A

New DNA molecules made up of 1 new and 1 original strand

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13
Q

How is DNA replicated

A

DNA helicase unzips the DNA by breaking the hydrogen bonds
this seperates the DNA molecule into 2 template strands
Activated nucleotides join by complementary base pairing to the 2 template strands
Hydrogen bonds form between free nucleotides and each template strands
DNA polymerase joins sugar phosphate backbone by forming phosphodiesther bonds between nucleotides
Semi conservative model: new DNA molecules made up of 1 new and 1 original strand
Each molecule forms a double helix

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14
Q

How’s does DNA’s structure allow replication

A

Double stranded- each strand acts as a template
H-bonds- easily broken
Base pairing- complementary bases hold strands together

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15
Q

How was the Messelson-Stahl experiment carried out

A

They grew E-coli on nitrogen15- all of ther DNA was nitrogen15
They then transferred bacteria to nitrogen14 substrate
This means that DNA replications from now on can only use Nitrogen14
Using centrifugation, the DNA from each subsequent replication can be seperated
The band pattern reveals the mechanism

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16
Q

What is the conservative model for DNA replication

A

One of daughter molecules ends up with new DNA and other molecule ends up with old

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17
Q

What is the Dispersive model of DNA replication

A

Daughter DNA molecules made up of part new molecule and part original strand (hybrid)

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18
Q

When does DNA replication occur?

A

synthesis phase of cell cycle

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19
Q

what happens after DNA replication

A

mitosis

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20
Q

what are the monomers of DNA

A

nucleotides

21
Q

How do nucleotides join

A

By a bond between Phosphate group of one molcule and pentose sugar of other molecule

22
Q

What is the name of the bond that joins nucleotides

A

phosphodiesther bond

23
Q

What are the bases of DNA

A

Adenine
Thyamine
Guanine
Cytosine

24
Q

What are the bases of RNA

A

Adenine
Uracil
Cytosine
Guanine

24
Q

What are the bases of RNA

A

Adenine
Uracil
Cytosine
Guanine

25
Q

What is the structure of RNA

A 
smaller than DNA
less stable than DNA
single stranded
ribose sugar
AUCG
26
Q

What is the structure of DNA

A

Double stranded
Complementary base pairs
Hydrogen bonds between bases
Forms ‘double helix’

27
Q

How does the structure of DNA relate to its function

A

very long molecule means holds alot of information
double stranded means both strands used as templates in replication
helix means compact
sugar phosphate backbone provides chemical and physical protection of bases
weak hydrogen bonds means molecule easily broken for replication
strong hydrogen bonds means stable molecule
base sequence codes for primary structure of proteins

28
Q

What does ATP stand for

A

adenosine triphosphate

29
Q

How is ATP synthesised

A

ADP and inorganic phosphate react to make ATP. It’s a condensation reaction and the enzyme involved is ATP synthase.

30
Q

How is ATP broken down

A

ATP reacts to form ADP and inorganic phosphate. This is a hydrolysis reaction which means energy is released and the enzyme involved is ATP hydrolase.

31
Q

Why is ATP so useful as a molecule

A

single bond broken
therefore immediate energy release
small/manageable amount of energy release
Rapid synthesis as only a single bond is formed
soluble so diffuses around cell easily

32
Q

What is an antigen

A

A foreign protein which stimulates an immune response

33
Q

what is an antibody

A

A protein specific to an antigen and secreted by plasma cells

34
Q

What is the humoral response

A

B cells and antibody secretion

35
Q

What is the structure of antibodies

A

quartenary structure with two heavy polypeptide chains bonded by disulfide bonds to two light polypeptide chains

36
Q

what does each polypeptide chain consist of

A

constant region and variable region

37
Q

What does the constant region determine

A

the mechanism used to destroy pathogens

38
Q

What is the variable region

A

amino acid sequence (at tip of Y) and where the antibody attaches to the antigen to form an antigen-antibody complex

39
Q

what is the difference between active immunity and passive immunity

A

Active is when antigen required, B memory cells produced, long term immunity and takes a long time whereas Passive immunity doesnt require antigen, no B memory cells produced, short term immunity and Immediate immunity

40
Q

how do you increase rate of diffusion

A

increase surface area
increase concentration gradient
decrease diffusion pathway

41
Q

how is gas exchange maximised in fish

A

many lamellae= high sa
each lamellae v thin= short diffusion pathway
countercurrent flow= maintains steep conc gradient across whole length of lamellae
blood oxygen conc always greater than water oxygen conc
ventilation replaces o2 depleted water
blood circulation replaces o2 rich blood

42
Q

what is the counter current flow and how does it maximise gas exchange

A

water flows in one direction over gills and blood flows in opposite direction over lamellae
this results in highest o2 conc at one end and lowest o2 conc at other end
because of counter current flow o2 conc in water always higher than o2 conc in blood
therefore diffusion occurs across whole length of lamellae
therefore gas exchange maximised

43
Q

how does fish ventilate

A

mouth opens
bucal cavity volume increases therefore pressure decreases
mouth closes
buccal cavity volume decreases therefore pressure increases
causing operculum to open and water to flow through gills

44
Q

how is gas exchanged in insects

A

o2 diffuses down conc gradient from outside to cells

co2 diffuses out down its own conc gradient- independent of each other

45
Q

how does the exoskeleton minimise water loss

A

hydrophobic hard waxy coating on outside of body

46
Q

what happens during increased respiration rate in insects

A

Lactate produced in cells. Therefore creates difference in water potential. water absorbed by osmosis therefore increased surface area for gas exchange

47
Q

how do spiracles prevent water loss

A

they close

Biology (14 decks)

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