Biology Revision Flashcards b3 (OCR)

7/21/2019 Biology Revision Flashcards b3 (OCR)

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Functions of the blood

Plasma is a pale yellow liquid which carries just about

everything that needs transporting around your body.

- Red blood cells, white blood cells, and

platelets (used in blood clotting).- Water- Digested food products like glucose and amino

acids from the gut to all the body cells.- Carbon dioxide from the body cells to the lungs- Urea from the liver to the kidneys (where its

removed in the urine).- Hormones, they act like chemical messengers

- Antibodies, are proteins involved in the bodysimmune response

Red blood cells hae the !ob of carr"ing ox"gen

!ed blood cells transport o"ygen from the lungs to all

the cells in the body. #he structure of a red blood cell is

adapted to its function$

- !ed blood cells are small and have a biconcave

shape to give a large area to volume ratio for

absorbing and releasing o"ygen.- #hey contain haemoglobin, which is what gives

blood its colour % it contains a lot of iron. &n the

lungs, haemoglobin combines with o"ygen to

become o"yhaemoglobin. &n body tissues thereverse happens to release o"ygen to the cells.

- !ed blood cells dont have a nucleus % this frees up

space for more haemoglobin, so they can carry



#lood cells are designed for their functions

' dierent blood vessels$

) Arteries % carry the blood away from the heart*) Capillaries % these are involved in the e"change of

materials at the tissues') $eins % these carry the blood to the heart

+rteries carry blood under pressure

- eart pumps blood out at high pressure, so the artery

walls are strong and elastic.

- #he walls are thick compared to the sie of the whole

down the middle (the lumen) they contain thick layersof muscle to make them strong.



Continued

apillaries are really small

- +rteries branch into capillaries. apillaries are too small

to see.

- #hey carry the blood really close to every cell in the

body to e"change substances with them.

- #hey have permeable walls, so substances can diuse in

and out.

- #hey supply food and o"ygen, they take away wastes

like carbon dio"ide

- #heir walls are usually only one cell thick. #his increases

the rate of diusion, by decreasing the distance over



Continued%

/eins take blood back to the heart

- apillaries eventually join up to form veins.

- #he blood is at lower pressure in the veins so the walls

dont need to be as thick as artery walls.

- #hey have a bigger lumen than the arteries to help

blood 0ow despite the low pressure.

- #hey also have valves to help keep the blood 0owing in

the right direction



1et pics of arteries, veins and capilleries from te"tbook page 23



&ammals hae a double circulator" s"stem

#he 4rst system connects the heart to the lungs. 5eo"ygenated

blood is pumped to the lungs to take in o"ygen. #he blood then

returns to the heart.

#he second system connects the heart to the rest of the body.

#he o"ygenated blood in the heart is pumped out to the body. &t

gives up its o"ygen, and the deo"ygenated blood returns to the

heart to be pumped out of the lungs again.

6ot all animals have a double circulatory system (4sh dont).

#here are advantages to mammals having double circulatory

systems though. !eturning the blood to the heart after its picked

up o"ygen at the lungs, means it can be pumped out around the

body at a higher pressure. #his increases the rate of blood 0ow to

the tissues (i.e. blood can be pumped around the body much

faster), so more o"ygen can be delivered to the cells. #his is

important for mammals, because they use up a lot of o"ygen

1et pic of heart page 27



'he heart

#he right atrium of the heart receives deo"ygenated blood

from the body (through the vena cava). Plural of

atrium8atria.

#he deo"ygenated blood moves to the right ventricle, which

pumps it to the lungs (via the pulmonary artery).

#he left atrium receives o"ygenated blood from the lungs(through the pulmonary vein).

#he o"ygenated blood then moves through to the left

ventricle, which pumps it round the whole body (via the

aorta).

#he left ventricle has a much thicker wall than the right

ventricle. &t needs more muscle to pump blood round the

whole body, whereas the right ventricle only pumps it to the



(electie breeding

&t is when humans arti4cially select the plants r animals that

are going to breed and have their genes remain in the

population, according to what we want from them. 9rganisms

are selectively bred to develop the best features, which are

things like$

- :a"imum yield of meat, milk or grain.- 1ood health and disease resistance

- 9ther qualities like temperament(nature), speed andattractiveness

;asic process involved in selective breeding

- <rom your e"isting stock, select the ones which have

the best characteristics.- ;reed them with each other- =elect the best of the ospring and breed them

together.



'he main drawbac) is a reduction in the gene pool

#he main problem with selective breeding is that it reduces the

gene pool % the number of dierent alleles (forms of a gene) in

a population. #his is because the farmer keeps breeding fromthe best animals or plants % which are closely related. #his is

known as inbreeding.

&nbreeding can cause health problems because there>s more

chance of the organisms developing harmful genetic disorderswhen the gene pool is limited. #his is because lots of genetic

conditions are recessive % you need to alleles to be the same

for it to have an eect. ;reeding from closely related

organisms all the time means that recessive alleles are more

likely to build up in the population (because the organisms arelikely to share the same alleles).

#here can also be serious problems if a new disease appears,

because theres not much variation in the o ulation. =o if one



*enetic engineering

;asic idea behind genetic engineering is to move genes

(sections of 56+) from one organism to another so that it

produces useful biological products.

+dvantage

?ou can produce organisms with new and useful features very

quickly.

5isadvantage

#he inserted gene may have une"pected harmful eects.

@.g. genes are often inserted into bacteria so they produce

useful products. &f these bacteria mutated and becamepathogenic, the foreign genes may make them more harmful

and unpredictable. People also worry about engineered 56+

escaping % e.g. weeds could gain rogue genes from a crop



+mportant stages in genetic engineering

) #he gene thats responsible for producing the desirable

characteristic is selected (i.e. the gene for human

insulin).

*) &ts then cut from the 56+ using enymes, and isolated.

') #he useful gene is inserted into the 56+ of another

organism (i.e. bacterium).

A) #he organism then replicates an soon there are loads of

similar organisms all producing the same thing (i.e. lots

of bacteria producing human insulin).

examples of genetic engineering

&n some parts of the world, the population heavily relies on rice

for food. &n these areas, vitamin + de4ciency can be a problem,

because rice doesnt contain much of this vitamin, and other

sources are scarce. 1enetic engineering has allowed scientists

to take a gene that controls beta-carotene production from

carrot plants, and put it into rice plants. umans can then

change the beta carotene into vitamin +.

#he gene for human insulin production has been put into

bacteria. #hese are cultured in a fermenter and the human

insulin is simply e"tracted from the medium as they produce it.

=ome plants have resistance to things like herbicides, frostdamage and disease. Bnfortunately its not always the plants

we want to grow that have these features. ;ut now thanks to

genetic engineering we can cut out the gene responsible and

'h l d thi l i i l d i ti



'here are moral and ethical issues inoled in genetic

engineering%

=ome people think its wrong to genetically engineer some

organisms purely for human bene4t, this is a particular problem in

the genetic engineering of animals, especially if the animal suers

as a result.

People worry that we wont stop at engineering plants and animals.

&n the future, those who can aord genetic engineering might be

able to decide the characteristics they want their children to have,and those who cant aord it could become a genetic underclass.

#he evolutionary consequences of genetic engineering are unknown,

so some people think its irresponsible to carry on when were not

sur what the impact on future generations might be.

To insert a genetically engineered animal organ into a

human, without having it rejected. The organ could be

genetically altered with human genes to trick a human’s



*ene therap"

&t involves changing a persons genes in an attempt to cure

genetic disorders. =cientists havent got it to work properly.

* types of gene therapy

- #he 4rst would involve changing the genes in the boy

cells , particularly the cells that are most aected by

the disorder. <or e"ample, cystic 4brosis aects the

lungs, so therapy for it would target the cells lining

the lungs. #his wouldnt aect the individuals

gametes (spermCegg) though, so any ospring could

still inherit the disorder.- #he second type involves changing the genes in the

gametes. #his means that every cell of any ospringproduced from these gametes will be aected by the

therapy % and the ospring wont suer from the

disease. #his therapy is currently illegal.



*ene therap" inoling gametes is controersial

debateable.

- <or e"ample, it might have une"pectedconsequences, which cause a whole new set of

problems. #his problem may then be inherited by

the future generations.- #here>s a fear that this type of therapy could lead

to designer babies which again is unfair.

Cloning

lones are genetically identical organisms

lones occur naturally in plants and animals, identical

twins are clones of each other.



Cloning an adult animal is done b" transferring a cell

nucleus

#he 4rst mammal to be successfully cloned from an adult cell

was a sheep called dolly. 5olly was produced visa nucleartransfer. #his involves placing the nucleus of a body cell into an

egg cell.

#he nucleus of a sheeps egg cell was removed % this left the egg

without any genetic information

+nother nucleus was entered in its place. #his was a diploid

nucleus from an udder cell of a dierent sheep (the one being

cloned) and had all its genetic info.

#he cell was given an electric shock, so that it started dividing bymitosis (as if it were a normal fertilised egg).

#he dividing cell (now an embryo) was implanted into the uterus



#ene/ts of cloning

loning allows you to mass produce animals with desirable

characteristics, e.g.

- +nimals that can produce medicine in their milk could be

developed by genetic engineering and then cloned.

!esearchers have managed to transfer genes that

produce useful proteins into sheep and cows. #his means

the animals can produce things like blood clotting agentfactor /&&& (used for treating haemophilia).

- +nimals (like pigs) that have organs that are suitable for

transplantation into humans could be developed by

genetic engineering and then cloned. #his would ensure

constant supply of organs for transplant % organs from

human donors are currently in short supply. #here are

issues to consider with this type of transplant though %

#ene/ts of cloning continued%

- uman embryos could be produced by cloning adult

cells. #he embryos could then be used to supply stem

cells for stem cell therapy. #hese cells would have

e"actly the same genetic info as the patient, reducing

the risk of rejection

Ris)s of cloning

- #here is evidence that cloned animals might not be as

healthy as normal ones

- loning is a new science and it might have

consequences that were not yet aware of.



Cloning humans is a possibilit" - with a lot of ethical

issues

- #here would be lots of surrogate pregnancies, probably

with high rates of miscarriage or stillbirth.

- lones of other mammals have been unhealthy and

often die prematurely % which means human clonesmight too.

- @ven if a healthy clone was produced, it might be

psychologically damaged by the knowledge that its

just a clone of another human being.

Cloning plants



Cloning plants

1ardeners are familiar with taking cuttings from good parent plants

and then planting them to produce genetically identical copies .

loning plants is easier than cloning animals, because plant cellskeep their ability to dierentiate % animals lose this ability at

an early stage.

ommercial cloning involves tissue culture

<irst, choose a plant you want based on its characteristic % e.g. a

beautiful 0ower

?ou remove several of small pieces of tissue from the parent plant.

?ou get the best result if you take tissue from fast growing

root and shoot tips

?ou grow the tissue in a growth medium containing nutrients and

growth hormones. #his is done under aseptic (sterile) conditions



































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Biology Revision Flashcards b3 (OCR)