Control Systems

Question 1

What is a circadian rhythm

Answer 1

A biological rhythm that happens over 1 day

Question 2

What is and what does a biological clock do

Answer 2

A timing mechanism in the brain that regulates what happens in our bodies over a 24 hour periods such as release of hormones

Question 3

What are hormones

Answer 3

Chemical messengers that are made in the body and travel in the blood stream. They affect different parts of the body

Question 4

What makes us tired

Answer 4

A hormone called melatonin and is released around ten pm and levels of it drop in the morning so we are more alert

Question 5

How is the biological clock kept in sync

Answer 5

Exposure to day and night, this is why we get jet lag

Question 6

Name two plant circadian rhythms and explain them

Answer 6

Flowers open in day and close at night to make sure they are ready for insects in during the day and protect pollen during the windy, cold and damp night
Nestor is only produced in the day when insects are around and more likely to visit

Question 7

What is photoperiodism

Answer 7

The response to changing lengths of daylight

Question 8

Give examples of photoperiodism

Answer 8

Seeds germinate when they sense longer day length, spring

Trees shed their leafs as daylight becomes less

Question 9

What are alkaloids

Answer 9

Poisonous chemicals produced in leafs to protect them from pests

Question 10

Why are poisons in plants only made at certain times

Answer 10

It uses lots of energy so producing them when there are no pests (night) would waste a lot of energy so they are only made during the day

Question 11

What are pathogens

Answer 11

Organisms that cause disease such as potato blight

Question 12

Give 3 examples of useful plant poisons and the plant they’re from

Answer 12

Digoxin found in foxgloves can cause heart attacks if too much is used but in small doses it can benefit the heart so is used to treat heart problems
Quinine is produced by cinchona trees and can treat malaria
Aspirin is produced in willow trees and can treat pain and fever

Question 13

How and who discovered microorganisms caused disease

Answer 13

Louis Pasteur proved it by putting broth in a straight neck flask and a swan neck flask. The straight neck broth went bad after a few days, broth in swan neck stayed fresh for longer as microorganisms got trapped in the swan neck

Question 14

What is the process of keeping things free from microorganisms

Answer 14

Aseptic techniques

Question 15

Give an example of an aseptic technique

Answer 15

Pasteurisation involves heating the food such as milk before storing it to kill bacteria in it

Question 16

How can the amount of bacteria in something be measured

Answer 16

Use resazurin dye that indicates oxygen levels. It’s blue when high oxygen levels and pink when they’re low. If there is lots of bacteria, lots of oxygen will be used up so it’ll be pink

Question 17

What are antigens

Answer 17

Chemicals on the outer surface of all bacteria and cells

Question 18

How does our immune system use antigens

Answer 18

Foreign antigens can be detected by the immune system which then destroys them and the foreign cells

Question 19

What are antibodies

Answer 19

Chemicals that are released by lymphocytes that stick perfectly onto antigens and destroy the cell

Question 20

How does a vaccine work

Answer 20

A weakened or dead pathogen is injected into the body. The body detects the foreign antigens and produces lymphocytes with antibodies that perfectly fit the foreign antigens. These then divide to make more and more of these lymphocytes with matching antibodies. Some of these lymphocytes release lots of the antibodies to destroy the foreign pathogen whilst others become memory lymphocytes that remain in the body so it can quickly respond if that pathogen ever re enters the body

Question 21

Pros and cons of immunisation 3 each

Answer 21

Risks:
Person often gets swelling or redness around vaccination site
Some children may get a mild form of the disease they are being vaccinated against
Very rarely, the person may suffer and allergic reaction

Advantages:
Person becomes immune to disease without having to suffer from it
A lot lower chance of long lasting harm from diseased they are vaccinated against
If enough people are vaccinated, the disease becomes rare and even unvaccinated people are unlikely to get it

Question 22

What is an infection

Answer 22

The entry of a pathogen into the body

Question 23

What is the primary response to an infection and explain

Answer 23

The first time an a pathogen enters the body where only one or two lymphocytes recognise it so it takes a while for them to divide and release antibodies to destroy it. This is why it’s usually at least a few days before the infection goes away

Question 24

What is the secondary response to an infection and explain

Answer 24

Where a pathogen enters the body but not for the first time so many memory lymphocytes recognise it and quickly divide and release antibodies so more often that not, the pathogen is destroyed before symptoms show

Question 25

What are monoclonal antibodies

Answer 25

Many identical antibodies

Question 26

What does a lymphocyte that makes antibodies called and what can't it do

Answer 26

It becomes a B lymphocyte and can no longer divide

Question 27

How can monoclonal antibodies be made in large quantities and what is the new cell called

Answer 27

By combining a B lymphocyte with a cancer cell so it can still divide many times whilst making antibodies. This is called a hybridoma

Question 28

Give two uses of monoclonal antibodies and explain them

Answer 28

Antibodies that stick to a hormone called HGH is used in pregnancy tests as this hormone is released when the woman is pregnant so if the monoclonal antibodies stick to the hormone, there is a colour change They can be made slightly radioactive and made to stick to thighs such as cancer cells so they can be detected with detectors to show where the cancer is

Question 29

What are metabolic reactions

Answer 29

Reactions that take place in the body and produce waste products

Question 30

Name two waste products, where they're from and how they're removed

Answer 30

Urea from liver cells made from excess amino acids. Removed from blood by being filtered by the kidneys Carbon dioxide made from respiring cells and removed though the lungs

Question 31

What do the kidneys do

Answer 31

Blood enters it though renal arteries where it is filtered and waste products such as urea is filtered out to form urine. The clean blood flows out of the renal veins

Question 32

What happens in the urinary system

Answer 32

Dirty blood enters kidneys through renal arteries Kidneys clean the dirty blood and form urine Clean blood exits kidney through the renal vein Urine goes through ureters from kidneys and into bladder Urine exits body through urethra

Question 33

Why are kidneys important

Answer 33

If they stop working, poisonous urea will build up in the blood and won't be turned and removed as urine

Question 34

What is the criteria for a kidney so it can be put into someone else and explain

Answer 34

Must be similar to patients cells as otherwise, immune system of patient will recognise the foreign antigens on the doner kidney and will destroy it Must be healthy else no point.

Question 35

What is and what does a dialysis machine do

Answer 35

It's like an electric kidney, it cleans the blood if kidneys can't do it. Someone without healthy kidneys may have to be connected to it for several hours several times a week

Question 36

What are nephrons

Answer 36

Tiny microscopic tubes in kidneys

Question 37

What are the parts of a nephron

Answer 37

``` Glomerulus Bowmans capsule Convulated tubes Loop of henlé Collecting duct ```

Question 38

How does a nephron work

Answer 38

Blood from renal arteries enters network of capillaries ( glomerulus) Gloerulus sits in bowman capsule which has lots of little wholes that filter out small molecules such as water, glucose and urea whilst larger molecules such as proteins and blood cells stay in the glomerulus Some substances are réabsorbed through the nephron walls such as water and glucose ( selective reabsorbtion and osmosis of water) The rest of the liquid leaves the end of the nephron into the ureter as urine

Question 39

How is water controlled in the body and what kind of mechanism is it

Answer 39

It's an example of negative feedback Brain detects concentration of plasma in blood If low as lots water, pituitary gland releases less ADH hormone so kidneys reabsorb less water so urine is more dilute If high as not much water, pituitary gland releases more ADH so kidneys reabsorb more water so urine more concentrated

Question 40

What is negative feedback

Answer 40

If a faster increases, something will change to decrease that factor

Question 41

What is the menstrual cycle

Answer 41

A 4 week cylcle where an egg is released through ovulation, the uterus lining thickens for the egg, a while later, the lining breaks down along with the egg and is released from the body through menstruation.

Question 42

Timeline of what happens in menstrual cycle

Answer 42

Week one, menstruation takes place, period Week two, lining of uterus is built up again Day 14, ovulation takes place, egg released Days 14-16, fertilisation most likely Week 3-4 uterus lining continues to build up

Question 43

What are the 4 hormones that control menstrual cycle, explain them and where they're from

Answer 43

Oestrogen: high levels stimulates release of more LH. Released from ovaires. Stimulated by maturing egg follicles Progesterone: inhibits release of LH and FSH. Released from ovaries. Released after ovulation when follicle becomes a corpus luteum. LH: surge of this triggers ovulation. Released from pituitary gland. Triggered by high levels of oestrogen FSH: causes growth and maturation of egg follicles. Released in low levels of progesterone from the pituitary gland.

Question 44

What happens to menstrual cycle after fertilisation and why

Answer 44

It stops as corpus luteum continues to release progesterone so LH and FSH aren't released so no ovulation

Question 45

What are the parts of a human egg cell (specific)

Answer 45

Haploid nucleus only one set of chromosomes, not pair Cytoplasm with nutrients Lipid droplets

Question 46

Name parts of sperm (specific)

Answer 46

Head (acrosome) containing enzymes that digest egg wall to get into it Haploid nucleus Middle section with mitochondria to create and release energy by respiration Tail for swimming

Question 47

What happens in fertilisation

Answer 47

Hundreds of sperm compete to enter the egg first Once one does, egg cell membrane quickly changes so no more sperm can enter The two haploid cells fuse to make a diploid zygote cell He zygote divides many times to create an embryo which embeds into the uterus lining to grow and develop

Question 48

Name and briefly explain 4 fertility treatments

Answer 48

IVF, egg removed from women, fertilised by sperm in pétri dish, one or two of strongest embryos put into uterus to develop Egg donation, hormones given to another woman so she release several eggs, then fertilised by IVF and embryo placed into infertile woman Surrogate mother, pairs gamates fertilised though IVF, embryo placed into surrogate mother who develops it and gives birth to it Hormones, make woman release more eggs to increase chance of fertilisation, however it increases chance of having several children

Question 49

What is a phenotype

Answer 49

What an individual looks like as result of chromosomes, e.g. Male, female

Question 50

What is genotype

Answer 50

The genetic material of an individual

Question 51

What are alleles

Answer 51

Different forms of the same gene

Question 52

Genotype and phenotype chart for haemophilia gene

Answer 52

XH XH female, normal clotting, no haemophilia, not carrier XH Xh female, normal clotting, no haemophilia, carrier Xh Xh fœtus doesn't normally develop XH Y male, normal clotting, not carrier Xh Y mâle, haemophilia, carrier