Human Bio F224 revision

  • Created by: Hannah
  • Created on: 12-12-12 18:08

Describe structure of ATP

- Nitrogenus base (Adenine)

- Ribose sugar 

- 3 phosphate groups

- phosphorylated nucleotide 

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Explain decarboxylation and dehydrogenation

Decarboxylation- removing carboxyl group 

Dehydrogenation- removing hydrgoen group

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State how RQ is calculated

Volume of CO2 produced (divided by) Volume of O2 consumed

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State how RQ is calculated

Volume of CO2 produced

(divided by)

Volume of O2 consumed

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Describe process of Transcription

- DNA unzips breaking the hydrogen bonds

- DNA acts as a sense strand 

- RNA nucleotides move towards template

- complementary base pairing

- RNA contains uracil instead of thymine which pairs up with adenine

- RNA copies entire DNA sequence from first triple base codon to final triple base stop codon

- MrNA detaches and leaves nuclues through nuclear pore and enters cytoplasm to associate with a ribosome

-Polynucleotide formed from condesation reaction

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Describe process of Translation

-mRNA attaches to ribosome on rough endoplasmic reticulum or free floating in cytoplasm

- tRNA attached to specific animo acids which they picked up in cytoplasm and brings towards MrNA (activation)

- mRNA contains triple base codons which are complementary to anticodons to the tRNA molecule 

- tRNA binds to mRNA 

- the sequence of codons on mRNA determines the sequence of amino acids

- peptide bonds form between amino acids and polypeptide chain forms

- tRNA detaches and mRNA returns to cytoplasm to be activated again

- polypeptide chain then combines with heam, modified in glogi appartus and endoplasmic reticulum where it is then recognised as heamoglobin

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Differences between DNA and RNA

DNA                                                      RNA

double stranded molecule                     single stranded molecule

Thymine                                              Uracil

contains Deoxyribose                           Ribose sugar

one form                                              3 forms: r,t,m

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Explain the Bohr shift/effect

-carbon dioxide increases increases H plus ions as carbonic acid has disassociates doe to the action of carbonic anhydrase

- H plus binds to haemoglobin

-haemoglobin acts as a buffer

- haemoglobinic acid formed

- Lowers affinity of O2 for haemoglobin

- curve is shifted to right

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Explain the oxygen dissociation curve

 -at low PPO2 its difficult for O2 to bind with hb so the curves shallow.

- as first hb binds with O2 the shape of hb is disorted making it easier for the successive O2 molecules to bind, hence a steeper curve.

- at the end theres high PP02 which makes it difficult to fully saturate hb so the graph platueas

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Define Oxygen deficit

difference between O2 demand and supply due to inadequate blood supply to the muscles

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Define EPOC/oxygen debt

total 02 consumed in excess of pre-exercise level

needed to: replenish stocks of oxyhb and oxymy

                regenerate creatine phosphate

                lactate produced during anaerobic respiration is transported to the liver where it is converted to pyruvate

               oxidise pyruvate into links and krebs cycle

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How can athletes performance be enhanced at high a

- low PP02 at high altitudes

- more erythropoitein 

-more red blood cells

- so more Hb

- more 02 carried

to sustain aerobic fitness

and more energy realeased through ATP production

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Explain carbohydrate loading

endurance athletes will attempt to deplete their stores of carbohydrates and then a few days prior to their race they will load up on carbs (10 percent of own body mass)

which maximises glycogen stores in muscle cells so it can be converted to extra energy (atp) during aerobic respiration

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What is RHEPO and the risks

recombiant human eyrthpoiten 

erythopoietin is genectically engineered gene which is injected into blood plasma

triggers bone marrow and stimulates realease of RBC'S

more 02 can be transported for aerobic respiration


increases viocosity of blood which can cause clots and block capillaries

leading to heart attack/stroke

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Whats blood doping and the risks?

transfusion of own rbc's

after blood volume has been constipated / plasma removed

increase in rbc's 

leads to increase in 02 transport


increases viscosity of blood which can clot and block capillaries

leads to heart attack/stroke

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Explain estrogen inhibitors/ anabolic steroids and

stimulates anabolic reactions such as protein synthesis and promote growth

increase in muscle mass/strenght/size

increase work rate

increase aggression 


mimics actions of sex hormones can cause acne, breasts, hair loss etc

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Explain creatine monohydrate

increases muscle energy reserves

high energy compound

increases mental awareness

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Why is the structure of glycogen an excellent stor

- provides a ready energy store

- insoluble 

- doesnt affect water potential of cell

- compact shape

- easily broken down/hydrolised to glucose

-large no of terminals for enzyme action

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How much exercise is needed for improvement?

- 20-60 mins of exercise a day 3-5 times a week

- aerobic exercise such as swimming running etc

- working at 70% of vo2 max and 60-85% of max heart rate

- continous, interval,fartlek training

- warm up and down

- medical health checks: asthma

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Define respiratory substrate

substance required for cellular respiration to dervive energy from e.g carbohydrates, fats, proteins

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What are long term effects of exercise

- increased V02 max

-increased sixe and no. of blood vessels

- lower resting heart rate

- increased size and structure of muscles(hypertophy)

- increased glycogen stores

- increased max breathing rate,tidal volume and vital capacity

- positivie benefits to immune system and general well-being

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Outline the role played by calcium ions in contrac

- ca plus plus or calcuim ions realeased from sacroplasmic reticulum

- binds to troponin

- displaces tropomyosin

-changes shape

- binding site exposed

- myosin head binds to actin

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Describe how gene mutation can cause a change in t


- Changed sequence of triple codon

- differenent amino acid- valine

- hydrophobic r group

- causes polypeptide chain to fold up differently

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Describe how changed Hb can affect role of RBC's

-Makes them sickle shaped

-Hb less souble at low PP02 of oxygen/ forms polymer

- descreased surface area

- less o2 carried

- cells less flexible

- blocks blood capillaries

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Outline krebs cycle

takes place in matrix of mitochondria

acteyl coenzyme A combines with 4 carbon molecule oxaloacetate forming 6 carbon citrate

decarboxylated in series of enzyme linked steps to regenerate the 4 carbon compound

also dehydrogenated during the process realeasing hydrogen atoms and forming reduced NAD and FAD

regenerated compound can combine with acteyl conenzyme a and cycle starts again

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Explain how water is polar?

water contains oxygen atoms that are slightly negatively charged and hydrogen atoms that are slightly positively charged therefore this means the forces are attracted to each other and attracted to other water molecules.

water are attracted to other polar molecules and form a shell around ions that have slight charges which causes them to disslove, making water a good solvent.

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explain DNA damage and how its repaired?

DNA is damaged by uv light exsposure, ionising radiation and replication errors.

A proof reading mechanism is carried out by dna polymerase enzymes to correct mistakes.

After dna has replicated a second set of protein surveys the dna for mismatches in the base pairs

when dna has been damaged during the life of the cell enzymes cut out/excise the misparing nucleotides and dna polymerase and ligase repair the dna strands

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What are telomeres?

regulate cell division

protect genes on chromosones

DNA can be exsposed if telomeres get too short

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how are monozygotic and dizygotic twins formed?

monozygotic-develop from one zygote which splits to from two embryos

dizygotic- develop from two seperate eggs that are fertilised by two seperate sperm

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Consequences of multiple pregnancy?

Low birth weight

Still birth

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what does the surge of LH cause?

causes grofian follices to realease secondary oocyte

development of corpus luteum

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Why are birth rates higher in ethopia than britian

-Lack of contraception

- encourage large families for the work force

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Describe the role of prolactin?

During pregnancy: stimulates growth of mammary glands/breasts

inhibted by oestrogen/progesterone

Following birth of baby: increased with suckling which controls milk production/lactation 

increased as oestrogen/progesterone levels fall

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prolactin inhibts fsh and lh what does this mean

-prolaction follice not stimulated 

- oestrogen levels do not rise

- resulting in delay of menustration as entrometrium does not proliferate

- less chance of ovulating

- lower fertility

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what is Succession

- starts with uncolonised area

- of pioneer species

- series of recognisable stages

- progresses to final equilibrium stage/climax

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suggest how deflected succession could be caused





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how does intensive farming affect sustainability

- extensive turns to intensive

- non- renewable

- removal of waste

- high energy demand

- not recycled- fields not fertilised

- enviromental control in intensive

- increased use of processed foods

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whys rate of photosyn higher in tropical than temp

higher light intensity

warmer so enzymes work faster

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explain importance of producers in making energy a

converts light energy into potential energy

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explain why only small amounts of energy is avalia

some energy is lost in respiration, faeces and excretion

only energy for growth/tissues is passed on

humans will only select the best parts

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Discuss plants provide a more efficient way than m

- energy lost at each trophic level i s only 10 percent efficient 

- due to excretion/respiration/ movement 

- very little of the energy when eating meat is tranferred to humans

whereas plants make be more efficient as less trophic levels involved 

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Discuss factors that affect birth and death rate?

- Agriculture- modern methods of food production: use of fertilisers and pesticidies and selective breeding has resulted in greater food avaliablitly so this has increased birth rate in some countries due to having ample quantity of nutritous food

however food is not evenly disturbted between coutries and many people live in poverty and have a high death rate due to starvation or nutrient deficiency.

Medicine- the use of antibiotics and vaccines have improved a great deal and also infertility treatments have increased the birth rate and people are living longer due to being able to recieve organs and repair damaged body parts. however less economically developed countries are still isolated from medical advances

Infectious disease- treatment and the ability to control the spread of disease has had a positive affect on survival. birth rates have slightly increase but infant mortality has decreasing resulting in population growth. However theres a high raising threat of H.I.V which a proportion of africa live with which is uncurable and will die from adding to death rate.

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Explain how impact of rising human population will

-increased destruction of natural habitats as urban areas will increase with size

- increased depletion of earths fossil fuels as resources needed to provide energy

-continue depletion of food stocks such as ocean's fisheries

- overall decrease in biodiversity as wildlife cant out-compete humans(limitied space)

-increases problem of pollution and lan degradation

-introduction of non-native species which out- compete with natual species and alter habitat

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Discuss importance of biodiversity

medical- humans depend on other organisms for food, fibre and medicine. its estimated that almost half of medical perscriptions contain natural plant or animal product so without this we wouldnt survive

Astheic pleasure human get from interacting with other organisms e.g pets,parks,zoo

extinction of species deprive us from the opportunity to study and understand ecological relationships and our relationship with the ecosystem

ethical issue- its said humans have stewardship over the plant not owership.

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Explain how burning fossil fuels effects carbon cy

fossils fuels are remains of prehistroic plants or animals which contain hydrocarbons(stores of potential energy) when they are combusted the energy realeased can be used as electricity heat energy and they can be used to make plastics, clothing, petrol etc. the carbon trapped in fossil fuels is known as a carbon sink and when humans are burning more fossil fuels than are being produced more c02 is being produced in the atmosphere than removed leading to rise in atmospheric temperatures

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Explain how deforestation affects carbon cycle

Trees/forests act as a carbon sink so when it is cut down it realeases a lot of co2 into the atmosphere and levels of photosynthesis and respiration drop. if trees removed remaining vegatation is burned realeasing further co2

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What is a carbon footprint

measure of the impact that human activities have upon the environment and amount of greenhouse gases produced by these actitivities 

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How can individuals reduce their carbon footprint?

-turn off lights and electrical appliances

-replace all light bulbs with energy saving ones

-turn down central heating and water

-insulate lofts,walls, pipe, get double glazing fitted

-car share/cycle/walk

- do not buy bottled water

- buy organic food as has lower energy impact and fewer environmental impacts


primary carbon footprint-direct impact you have as an individual

secondaery carbon footprint- pollution caused by your buying habits

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What is carbon offsetting?

Carbon offsets are credits for reductions in greenhouse gases made in order to compensate for an emission elsewhere.

certified credits:tradeable and traceable credits that companies produce by having cleaner and greener methods of production

Voluntary credits:traceable but involve activities such as tree planting programmes, ususally apoted by individuals

Government grants are avaliable to become carbon neutral and to have so called zero emmisons

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What is carbon offsetting?

Carbon offsets are credits for reductions in greenhouse gases made in order to compensate for an emission elsewhere.

certified credits:tradeable and traceable credits that companies produce by having cleaner and greener methods of production

Voluntary credits:traceable but involve activities such as tree planting programmes, ususally apoted by individuals

Government grants are avaliable to become carbon neutral and to have so called zero emmisons

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What are the three types of muscle?




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What are cardiac muscles?

Cells are myogenic

heart control of autonomic nervous system

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What are skeletal muscle?

attached to bones, abdomen wall,diaphragm,facial muscles and extrinsic muscles of eye. primarily voluntary controlled by neurones of somatic system.

able to receive stimuli and respond to them by contracting.

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What are smooth muscle?

found in iris, ciliary body of eye,artery, vein and arteriole walls,walls of respiratory tract.

involuntary muscle and contraction is controlled by motor neurones of autonomic nervous system

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Whats the structure of sacromere?

within a myofibril, the mycrofilaments are arranged in a very ordered way forming a sacromere.

thin filaments- actin which consists of actin, tropomyosin and troponin.

thick filaments- myosin consists of bundles of polypeptide molecules with a globular head for binding to atp and actin.

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Explain process of muscle contraction

-nerve impulses reach skeletal muscle and stimulate neuromuscular junction(specialised synpase) ,stimulation causes realease if acetylcholine which travels across gap and binds to receptors on motor end plate

-impulse travels quickly through nerve fibre down t tubles system to sacroplasmic reticulum which realeases calcium ions that bind to troposin,which changes shape and removes tropomyosin.Actin and myosin binding sites are exsposed which makes them bind to each other

-myosin head which is usually attached to ADP but calcium ions activate enzyme myosin kinase which realease ADP so that the myosin head is free to bind

- in power stroke the myosin changes position and pulls actin so filaments slide past each other

- if ATP is avaliable myosin head will bind which realeases energy and actin+myosin return to originial position.As filaments slide attachments are made and broken. Contractions will continue until nervous stimulation ceases and calcium ions return to SR, fall in calcium ions causes actin to reattach to T and Tmyo so returning muscle fibres to oringinal shape

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Describe structure of Muscle fibre?

- made up of alternating light and dark bands, filaments of protein actin and myosin

-sacromere is key structure of muscle fibre and is characterised by having clearly identified z lines,A bands, H zones and I bands.

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Explain importance of T-tuble system in sacromere?

this structure stores and releases calcium ions when the neuromuscular junction are stimulated by nervous action. This realeases causes a change in behaviour of actin and myosin and allows contraction of mucle units.

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Wheres 3 places that phosphorylation occurs?

- mitochondrion


-cytoplasm during glycolysis

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Explain importance of coenzymes in atp production

- energy transfer molecules, a source of high energy electrons used  to synthesise ATP during oxidative phosphorylation

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products of krebs cycle?


reduced NAD and FAD

carbon dioxide


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Products of glycolysis



reduced NAD

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Describe fate of pyruvate in the absence of oxygen

in absence of oxygen there is no final acceptor of hydrogen to be passed on to and so NAD and FAD will not be regenerated. resulting in oxidation being blocked and link reaction,krebs cycle and electron transport chain will all stop.

the only energy aviable to the cell during anaerobic respiration is the ATP made by substrate level phosphorylation during glycolysis.For this is continue its important to remove pyruvate and to recyle NAD in order to make more ATP.

NAD is recycled as pyruvate becomes the hydrogen acceptor, the pyruvate then becomes reduced to lactate and NAD is made avialable to pick up another hydrogen so glycolysis can continue

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Describe fate of pyruvate in the absence of oxygen

in absence of oxygen there is no final acceptor of hydrogen to be passed on to and so NAD and FAD will not be regenerated. resulting in oxidation being blocked and link reaction,krebs cycle and electron transport chain will all stop.

the only energy aviable to the cell during anaerobic respiration is the ATP made by substrate level phosphorylation during glycolysis.For this is continue its important to remove pyruvate and to recyle NAD in order to make more ATP.

NAD is recycled as pyruvate becomes the hydrogen acceptor, the pyruvate then becomes reduced to lactate and NAD is made avialable to pick up another hydrogen so glycolysis can continue

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What can be a consequence of lactate build up

- can inhibt glycolysis so that eventually supply of ATP stops

- to prevent this the lactate is oxdised back to pyruvate by enzyme lactate dehyrogenase 

which is present in liver and muscle cells

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What happens to the lactate?

most lactate produced will leave muscle cells and enter blood-this can lead to lactic acidosis.

The lactate is a source of potential energy so its taken to the liver which contains enzymes (lactate dehydrogenase) that can convert lactate firstly back to pyruvate and then glucose. this glucose can be returned to muscles via the blood or stored as glycogen.

this is known a CORI CYCLE

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Outline oxidative phosphorylation?

-hydrogen atoms from reduced NAD and FAD are passed onto hydrogen acceptors in inner mitochondrial membrane. 

-hydrogen splits into protons and electrons.Electrons plass along cytochromes/electron transport chain which realeases energy and pumps protons into intermembrinal space.

- this sets up a proton gradient and protons diffuse along the concentration gradient and flow through a channel protein which is the Site of ATP synthase and the energy released is used in phosphorylation of ATP

-the final acceptor of hydrogen ions and electrons is oxygen which forms a molecule of oxygen

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Explain what happens when a molecule binds with el

no proton gradient set up 

so no protons flow through protein channel and ATP synthase

no ATP produced

no ATP for muscle contraction so cardiac muscles fail

no krebs cycle 

only glycolysis so lactate produced which can lead to lactate posioning 

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Where are fatty acids and amino acids broken down

Fatty acids- via conezyme A in the mitochondrial matrix- energy value 37 kJg-1

Amino acids- first deaminated and then enter glycolysis-energy value 17

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whats the difference between mRNA and tRNA

mRNA carries a complementary copy of genectic code for a polypeptide to the ribosome whereas tRNA molecules bind to specific amino acids and transport them to the ribosome.

mRNA is also single-stranded where as parts of tRNA are double-stranded

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Explain importance of ATP in muscle contraction

-ATP is broken down by the myosin head an ATPase. this realeases the myosin from actin, allowing the power stroke to be repeated and myofilaments to slide over each other to produce muscle contraction.

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explain what happens to Z lines A,B,H and I bands

                      at rest                                   during contraction

Z lines-  maximum distance apart                  move closer together

I band - Paler band                                        Smaller

A band-  H band seen                                   A band stays the same but H band                                                                                                   disappears

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What happens during spermatogenesis

sperm mother cell dividies by mitosis to become a primary spermatocyte,meiosis occurs forming firstly two haploid secondary spermatocytes and then four haploid spermatids which embed into sertoli cells and each one becomes mature sperm cell.

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actions of LH,FSH and oestrogen in menstrual cycle

LH- triggers secretion of oestrogen, maintains corpus leuteum and surge of LH causes grofian follice to realease secondary oocyte (ovulation).Stimulates releases of oestrogen

-FSH initates development of primary follicle

Oestrogen- promotes repair of endothmetrium and acts as an inhibitor of FSH. and acts as positive feedback for LH and FSH causing the surge of LH which triggers ovulation

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What do LH and FSH do to males?

LH and FSH act as gonadotrophins

LH stimulates production of testerone and FSH

and testerone control spermatogenesis

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What does oxytocin do?

stimulate uterine contractions

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Explain how using intrauterine insemination helps

- means sperm will not be destroyed in the vagina

-have greater chance of reaching fallopian tube to fertilise secondary oocyte

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Outline process of implantation

blastoyst makes it way to uterus and implants if endothemetrium is at correct stage, this starts an inflammination type process

endothmetrium grows around blastocyst forming a structure trophoblast which goes on to form a placenta

blastocyst develops into an embryo

hcg produced by blastocyst stimulates corpus leuteum to realease oestrogen and progesterone

progesterone maintains endothemetrium

oestrogen proliferates endothmetrium

inhibts lh and fsh

hcg peaks

progesterone decreases as placenta takes over

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What does GnRH do?

realeased by hypothamulus gland and stimulates the anterior pituitary gland to realease of LH and FSH, this can trigger development of follices and sperm

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Explain role of light in producing sugars and ATP

Light is captured by chloropyll. Energy is used to synthesise ATP by phosphorylation. Reduced NADP is formed and these two products from light- dependent reaction and used in light-independent to convert GP to TP

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outline process of gametogenesis

- germinal cells divide by mitosis to form oogonia

-this begin to divide by meiosis but only reach prohase 1 of first division of meiosis where they become primary oocytes

From puberty..

- some primary oocytes progess from prohase 1 to end of first division of meiosis

- the daughter cells are both haploid but only one becomes secondary oocyte the other forms a polar body

- 6-12 follicles mature each month but after one week one follice becomes dominant this becomes the grafian follicle

-secondary oocyte continues to develop but stops at metaphase 2  of meiosis, this is then realeased during ovulation and polar body deintergrate

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outline process of spermatogenesis

- each seminiferous tuble contain many diploid cells called spermatogonia which have developed from cells in tissue of germinal epithelium.

- the spermatogonia multiply by mitosis and then grow into primary spermatocytes 

- after this first division they develop into secondary spermatocytes and then after a second meiotic division they become haploid spermatids.

-these then differentiate and mature into sperm cells which are each capable of realeasing on ovum.

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Whats the role of female reproductive system

- produce haploid gametes

-oestrogen hormones

oviduct (fallopian tube) is the site of fertilisation, which normally leads to implantation and development of an embryo lining the fetus

from puberty until menopause the ovaries realease ova-female gametes.ova develop inside follices, and at ovulation are realeased into oviducts.

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What is the zona pellucida?

glycoprotein membrane surrounding the plasma membrane of secondary oocyte, the structure helps to protect the oocyte but also binds to sperm and initates the acrosome reaction

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Whats the role of hormones in gametogenesis

WOMEN fsh and lh levels rise in bloodstream, hormones bind to follice cells.

Follice cells mature and produce oestrogen

dominant follice secretes increasing levels of oestrogen

this initally inbits realease of lh and fsh but then stimulate surge of lh which causes graffian follice to release secondary oocyte

MEN lh binds to receptors on leydig cells in testes leading to secretion of testerone

testerone affects sertoli cells in testes, which makes them stimulate spermatogenesis

fsh binds to surface of sertoli cells making them more receptive to testosterone

rising blood testerone inhibt lh and excessive activity of sertoli cells inhibts fsh by secreting hormone inhibin

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What is semen made up of?

two-thirds seminal fluid from seminal vesicles which contains mucus and proteins to help swimming and fructose to provide energy

one third from prostate gland which fluid helps neutralise the vagina

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What is the mechanism to make sure only one sperm

sperm reach oocyte binds to glycoprotein receptors on zona pellucida which triggers acrosome reaction

one sperm penetrates outer layer of cells surrounding oocyte and zona pellucida sperm head reaches plasma membrane and binds to another receptor

cortical granules(lysosomes) are stimulated to fuse with zona pellucida and change proteins there this cortical reaction forms a fertilisation membrane stopping the entry of further sperm

presence of haploid sperm causes oocyte to final complete meiosis, sperm nuclues now enter oocyte enabling the two parental nuclei to fuse, cell become diploid and called a zygote

rapid mitosis takes place turning zygote into blastocyst (bundle of cells) which travels down oviduct towards uteus where it will implant into lining of the uterus.

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How does the birth control pill work

combination of oestrogen and progesterone and fools the body to think its pregnant the hormones take advantage of the negative feedback mechanism and gnrh is inhibted as result meaning that no follice is mature and no ovulation

- no protection against sti

- must remember to take it

- increased risk of thrombosis leading to heart attacks/strokes

- increased risk of breast cancer

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how do implants work?

implants are injected under the skin and slowing realeases progesterone which inhibits ovulation

- nearly 100 per cent effective

- no protection against STIS

- do not have to remeber to take the pill

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how does intra-uterine device work?

small peice of copper or plastic that is specially fitted into the uterus which prevents implantation of the embryos as stimulates inflammation response which prevents implantation and is toxi to sperm and embryo

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How does morning after pill work?

method of emergency contraception can only be used 72 hours after intercourse and contains taking large does of synthetic steriods which prevents implantation of embryo.

side effects such as abdonminal pain and sickness

some people use this as form of contraception

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What are ethical issue surrounding contraception

certain religious groups beleive preventing conception is destroying potential human life

contraception is unnatural method of preventing life

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Explain why only one sperm can enter egg

as soon as sperm enters the cortical reaction happens which changes the surface proteins of ovum forming a fertilisation membrane which stops the entery of any other sperm 

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Explain importance of uterine wall in implantion

allows blastocyst to rest and develop into an embryo

projections from the embryo and uterine wall go on to form a placenta

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Why does implantation cause inflammation first of

the blastocyst contains nuclear material and subsequent protens which are different to the mother therefore its recognised as foreign and female reacts as if it was an invading pathogen and lainches defense mechanism (inflammination)

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What is ovulation induction?

given drugs that inhibt oestrogen to promote the realease of GnRH and stimulate realease of FSH and LH from antieor pituary gland

this will induce ovulation and help development of follicles

risk of multiple pregnancies

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What is artificial insemination

injecting semen into the top of the uterus using a plastic tube

ICI- plastic cap placed at top of vagina for several hours to give sperm chance to enter the uterus through the cervix

IUI- places sperm near ovidcuts which is more successful

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How does in vitro fertilisation work

women is super ovulated using synthetic hormones so serval follices are produced

these follices are aspirated few hours before ovulation

the oocytes are removed using a suction device and placed into a test tube contain special medium

sperm are prepared and 100000 are added to oocyte in small petri dish

after 16-20 hours oocytes are checked to see if they have fertilised

the resulting embryos are then left to develop for two-three days in incubator

and transplanted back into uterus

providing many possible embryos these can be frozen and stored for later use

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Explain how female antibodies may act to destroy m

antibodies will cause sperm to clump together-agglutinate and be destroyed by phagocyctic cells 

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What is vanishing twin syndrome

occasionly a twin observed during ultrasound may vanish later on in pregnancy  this means the developing fetus has died and been reabsorbed back into womans body. this can occur as a result of chromosomal abnormality, fetal development problem or fault with placenta

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What is premature birth?

birth of baby before the standard peiod of time 40 week is completed

babies born before 37 weeks are seen as premature this can lead to:

poor neurological development

heart defects

respiratory distress syndrome or lung disease

blood problems- anaemia or jaundice

infections of urinary tract

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What does nitrfying bacteria such as nitrosomonas

turns amionium into nitrites and then nitrates

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What does nitrogen-fixing bacteria do (rhizobuim)

turns nitrates into atmospheric nitrogen

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Explain how a respirometer is used

- consists of two tubes linked by a manometer

- one contains live specimens and other acts as pressure control

- water bath to maintain temperature

- check initial fluid level in manometer

- leave for a set time

- measure distance moved by fluid in the set time

-reset manometer

-repeat at same temperature and calculate mean

-repeat at five different temperatures

-calculate rate distance/time

-plot graph rate vs temp

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