what are hormones
are special chemicals released from endocrinal glands. they are cell signalling molecules
differ between protein and steroid hormones
protein: cannot pass through csm, water soluble bind to receptr molecules on csm steroid: - not water soluble - can pass throggh csm -bind to receptor molecules in cytoplasm/ nucleus
what is a gland
a group of cells that produces or releases one or more substances through secretion
which glands control the menstrual cycle
ovaries, the anterior pituitary gland
role of oestrogen
maintains uterine lining, thickening of the endometrium, makes it grow and develop numerous blood capillaries. it inhibits FSH AND LH
what hormones are secreted by the ovaries
progesterone and estrogen- changes in uterus
what hormons escreted by anterior potuatry gland
FSH, LH
what causes the dom follicle to burst
the surge of LH causes the dom follicle tp bursts
how does oestrgoen and progestoje prevet fertiliziaton
- procedure: women takes 1 pill daily for 21 days annd stops for 7 days
- both oestrogen and progesterone inhibit secretion of FSH AND LH from a.p.g
- this prevents their conc from reaching a level that would stimulate ovulation
- progesterone reduces the ability of the sperm to ferrtilize the egg by making cervical mucous more viscous and so less easily penetrated by sperm
- stopping th epill aftr 21 days allows oes and prog to fall until endometrium is no longer maintaind
how does depolarisatioon occur in plants
occurs from outflow of -vely charged chloride ions, acction potentials travel along cell membranes from cell-cell through plasmodesmata
name some adaptations of venus fly trap
- stimulation of only 1 hair does not trigger closure for preventing closure during rain, debris, etc
- gaps between bars allow very small insects to leave to avoid wasting energy on a small meal
role of auxins, gibberelins
- influence many aspects of growth, which determines oveerall length of roots and shoots
- seed germination, stem elongation controlling
how does auxin help growth
1- auxin binds to receptor protein onn csm
- this stimulates ATPase proton pumps to pump H from cytoplasm - cell wall
- this acidifies the clel wall
- it actiates expansins due to decrease in ph, expansins loosen linkages bw cellulose microfibrils.
- cells absorb water by osmos
- pressure potential causes the ccell wall to stretch or elongate
how does gibberelins bring about germination
- seed absorsbs water
- this stimulates embryo to prod gibberelins
- gibbberelins diffuse to aleurone layer and stimulate ccells to produce amylase
- amylase hydrolyses starch moleccules and mkaes them soluble by converting them into maltose in endosperm
- maltose cnverted into glucose, trasnported to embryo where it can be used for respiraton for growth
