*[B1] Official AQA Biology Unit 1 Exam (5th June Friday)

I think the 6 MARK QUESTION could be on preparing uncontaminated culture mediums too! I just need to whiz through IVF and embryo screening and menstrual cycle but they are all pretty simple. We have also got until 12.15 tomorrow to revise!!! GOOD LUCK EVERYONE WHO IS SITTING THIS EXAM X

Does anyone understand the menstrual cycle? i dont get how it works....

I hope its on culture mediums, easy 6 marks. Just remember, after you state a point (e.g sterilise petri dish by heating it in an oven), say "to kill unwanted bacteria". Also, dont forget to say incubate the culture (at 25C) for the bacteria to grow

Does anyone understand the menstrual cycle? i dont get how it works....

Few things you need to know.

FSH produced in pituitary gland, stimulated maturation of egg
Oestrogen produced by ovary, inhibits FSH, stimulates LH, thickens lining of uterus
LH produced in pituitary Gland, release single matured egg into uterus/womb

Fertility drug (e.g IVF) contains FSH and LH
Contraceptive Drug contains Oestrogen and Progesterone however nowadays some only contain Progesterone as these have fewer side effects.

Hope this helps!! and good luck tomorrow

They could just say to mention about sterilising inoculating loops as an extra but I doubt it!

thanks that did help, but i thought IVF helped fertilization out of the body?

thanks that did help, but i thought IVF helped fertilization out of the body?

what happens is you get given hormones to cause more eggs to release, then these are removed and fertilised (by sperm) outside the body (in a test tube), this causes them to grow into an embryo. One or more embryos are then placed back into the uterus of the mother

FSH is released from the pituitarty gland which makes the eggs mature, and starts the production of oestrogen.
Oestrogen is produced in the ovaries and repairs the uterus lining, inhibits the production of FSH and starts the production of LH
LH is released from the pituitary gland and causes ovulation - the release of an egg - into the womb
progesterone maintains the uterus lining for 14 days, where the fertilisation of the egg could occur. If fertilisation doesn't occur the uterus lining is broken down

dont they use a host?

what do you mean by a host

a host mother, where the embryo is implanted after fertilisation, as the actual mother does not have a hospitable environment

a host mother, where the embryo is implanted after fertilisation, as the actual mother does not have a hospitable environment

Can you guys give me a way to remember the nervous / reflex system, I keep seeming to forget it. Is there a way of making it stick in my head?

Receptor detects change in stimuli
Impulse sent along sensory neurone
Diffusion of impulse across synapse as chemical neurotransmitter onto next neurone
In CNS (relay neurone) which coordinates response.
Synapse and then onto motor neurone
to Effector (muscle contracts or gland releases chemical)

Dont forget to make your answer specific to the question (what is the receptor and stimulus, is the effectroa muscle or gland...)

Would this be right for 6 mark if about culturing?

- Culture done in controlled conditions, preferably a lab to ensure the strain of bacteria being grown is pure to provide accurate results.
- Agar jelly and petri dish is sterilised, normally to exposure of UV light or autoclave in order to kill any bacteria.
- Inoculating loop is placed in bunsen burner, remain until it is bright red, again to kill any bacteria.
- Suspended in the bacteria and streaks made onto the agar jelly.
- Petri dish is closed with tape which has sight openings for oxygen to ensure no harmful anaerobic bacteria grow.
- Petri dish is incubated at around 25 degrees, to ensure optimum temp for bacteria. Any higher could lead to the growth of dangerous bacteria.

Have I left anything out?