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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
What are the bases of RNA
Adenine Uracil Cytosine Guanine
25
What is the structure of RNA
``` smaller than DNA less stable than DNA single stranded ribose sugar AUCG ```
26
What is the structure of DNA
Double stranded Complementary base pairs Hydrogen bonds between bases Forms 'double helix'
27
How does the structure of DNA relate to its function
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
What does ATP stand for
adenosine triphosphate
29
How is ATP synthesised
ADP and inorganic phosphate react to make ATP. It's a condensation reaction and the enzyme involved is ATP synthase.
30
How is ATP broken down
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
Why is ATP so useful as a molecule
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
What is an antigen
A foreign protein which stimulates an immune response
33
what is an antibody
A protein specific to an antigen and secreted by plasma cells
34
What is the humoral response
B cells and antibody secretion
35
What is the structure of antibodies
quartenary structure with two heavy polypeptide chains bonded by disulfide bonds to two light polypeptide chains
36
what does each polypeptide chain consist of
constant region and variable region
37
What does the constant region determine
the mechanism used to destroy pathogens
38
What is the variable region
amino acid sequence (at tip of Y) and where the antibody attaches to the antigen to form an antigen-antibody complex
39
what is the difference between active immunity and passive immunity
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
how do you increase rate of diffusion
increase surface area increase concentration gradient decrease diffusion pathway
41
how is gas exchange maximised in fish
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
what is the counter current flow and how does it maximise gas exchange
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
how does fish ventilate
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
how is gas exchanged in insects
o2 diffuses down conc gradient from outside to cells | co2 diffuses out down its own conc gradient- independent of each other
45
how does the exoskeleton minimise water loss
hydrophobic hard waxy coating on outside of body
46
what happens during increased respiration rate in insects
Lactate produced in cells. Therefore creates difference in water potential. water absorbed by osmosis therefore increased surface area for gas exchange
47
how do spiracles prevent water loss
they close

Biology (14 decks)

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