Unknown Student Guide Questions

Question 1

What are the 3 layers separating plasma from filtrate?

Answer 1

The capillary endothelium, the basement membrane on which the capillary cells lie, and the inner layer of the Bowman’s capsule

Question 2

Describe the inner layer of the Bowman’s capsule

Answer 2

Consists of podocytes, with foot-like processes which surround the capillaries but which have spacious gaps between them called filtration slits

Question 3

Describe adaptations in the tubules

Answer 3

Cuboidal epithelial cells which line tubule walls have many microvilli on the side in contact with the filtrate, and infoldings of the cell surface membrane on the side next to the capillaries. These adaptations increase the S.A. for reabsorption. The cells have many mitochondria to supply ATP for active transport

Question 4

What must a microorganism do to be pathogenic?

Answer 4

1) enter the host 2) colonise host tissue 3) evade host defences 4) cause damage to host tissue

Question 5

What is the difference between polymorphs and macrophages?

Answer 5

Polymorphs, more abundant but short lived, remain in blood until there is an infection when they move out of capillaries to site of infection. Monocytes are blood cells that can move out of blood capillaries into surrounding tissue where they develop into macrophages

Question 6

How are antigen-antibodies like the lock and key model?

Answer 6

For each antigen on the surface of a pathogen. there is a lymphocyte that carries a special protein receptor on its cell surface membrane that is complementary in shape.

Question 7

Where do B cells mature?

Answer 7

In the Bone marrow

Question 8

Where do T cells mature?

Answer 8

in the Thymus

Question 9

What happens after lymphocytes are sensitised?

Answer 9

A specific gene is activated, mRNA synthesized and proteins are produced. These proteins are either antibodies in B cells or membrane receptors in T cells. This process takes time. The sensitised lymphocyte is then cloned by mitosis.

Question 10

What do antibodies do?

Answer 10

Some neutralise toxins produced by bacteria, some clump or agglutinate bacteria before they are engulfed by phagocytic cells (antibodies are agglutinins), some attach to viruses to prevent entry of host cells, some destroy bacterial cell walls causing cell lysis, some antibodies attach to bacteria enabling phagocytic cells to identify them

Question 11

What are antigens / antibodies?

Answer 11

Antigens are foreign while antibodies are produced in body by b cells

Question 12

Why can being given the wrong blood cause agglutination?

Answer 12

Anti-a and anti-b are agglutinins

Question 13

What is the difference between agglutination and clotting?

Answer 13

Agglutination is the sticking together of RBC, clotting involves the formation of fibrin and only involves RBC in that they might become enmeshed in network of fibres

Question 14

Outline auxin action

Answer 14

Produced in cells of the apical meristem. diffuse down shoot towards zone of elongation. bind to specific receptors on cell surface membrane of newly formed cells. this causes membrane pumps to move hydrogen ions out into cellulose cell wall. the acidification of cell walls activates agents which loosen the linkages between cellulose microfibrils, allowing slippage between them, and making cell wall more flexible. the cells absorb water by osmosis and the flexible cell walls allow the cells to expand as the water exerts increased hydrostatic pressure against them. the more auxin that is received in the zone of elongation, the more this effect allows cells to expand

Question 15

What does positively phototrophic mean

Answer 15

Grows towards light

Question 16

How is the photoperiod measured?

Answer 16

By phytochrome pigments, P660 and P730

Question 17

What wavelength does P660 absorb?

Answer 17

red light

Question 18

What wavelength does P730 absorb?

Answer 18

far-red light

Question 19

Why is P660 converted to P730 in the day time?

Answer 19

Sunlight contains more light of wavelength 660nm than 730nm therefore P660 is converted to P730

Question 20

What are the 3 parts of a neurone?

Answer 20

A cell body (centron) which contains the nucleus and other organelles, and has a number of cytoplasmic extensions
Extensions called dendrons (or dendrites if they’re small) which transmit impulses to the cell body
Extensions called axons which transmit impulses away from the cell body and terminate in synaptic bulb.

Question 21

What is the resting potential?

Answer 21

-70 mV (millivolts) (negative 70)

Question 22

What is the critical potential difference?

Answer 22

Around -55mV

Question 23

What is saltatory conduction?

Answer 23

The action potential jumps from one node of ranvier to the next

Question 24

What are rods sensitive to?

Answer 24

dim light

Question 25

What are cones sensitive to?

Answer 25

bright light, but are able to discriminate fine detail and distinguish different wavelengths of light/

Question 26

Where are cones concentrated?

Answer 26

At the fovea, the centre of the retina.

Question 27

Where are rods found?

Answer 27

Around the periphery of the retina

Question 28

What do rods and cones synapse with

Answer 28

with bipolar neurones which in turn synapse with neurones of optic nerve

Question 29

What is retinal convergence?

Answer 29

many rods synapse with each bipolar neurone and many cells connect with each neurone of the optic nerve

Question 30

How does light travel in the retina?

Answer 30

Light passes through the neurones before reaching the outer segments of the rods and cones. The consequence of this is that for the neurones to leave the eye they must pass through the layer of photoreceptors creating an area devoid of receptors - the blind spot

Question 31

What happens when light hit rhodopsin?

Answer 31

rhodopsin breaks down into retinal and opsin. This results in a change in the membrane potential of the rod cell and creates a generator potential. This causes a change in the membrane potential of the neighboring bipolar neurone, with which the rod cell synapses. The bipolar cell releases transmitter substance into its synapse with a neurone of the optic nerve. If sufficient transmitter is released, an action potential is generated in the neurone of the optic nerve and transmitted to the visual centre of the brain

Question 32

How do we explain summation (in the eye)

Answer 32

With low-intensity stimuli, generator potentials have an additive effect and there is enough transmitter released to reach threshold for an action potential to be generated in a neurone of the optic nerve

Question 33

What is dark adaptation?

Answer 33

Rhodopsin is resynthesized in the rods. this requires ATP from mitochondria. the rate of resynthesis is sufficient for the rods to continue functioning in dim light, but in bright light the rhodopsin is almost entirely bleached. It takes about 30 minutes in darkness for all the rhodopsin to be reformed and so for the rods to become functional, this is dark adaptation

Question 34

Describe what we see through succession

Answer 34

(Based off N. America) During pioneer stages we see lichens, then moss, then herbs and weeds. In the intermediate stages we see grasses, then shrubs, then pines, spruces, chestnuts and immature oaks. At the climax community we see oaks, hickories, chestnuts, maples

Question 35

What do we see in secondary succession?

Answer 35

annual plants, then grasses and perennials, then shrubs and small trees, then young woodland trees, and finally mature woodland at the climax

Question 36

What is zonation

Answer 36

Different communities are present at the same time, distributed as bands or zones along an environmental gradient

Question 37

How do we calculate efficiency of energy transfer>

Answer 37

(energy in one trophic level/energy in previous trophic level) x 1000