Experiment 4 : Effect of temperature on enzymatic activity

Experiment 4 by L6ScZeta 2012

Enough or not?...enough or not??.....

 



One drop...two drops...three drops........

















Now...see this...this is how to hold it...






Where is the reading???

 

 

 

 

 

 

 

 

 

 





Wow....this stop watch is awesome!



 Experiment 4 by L6ScGamma 2012




L6ScGamma in action.......

Is this mine?...I think this is yours.........wait......I think.......

Give a BIG smile!...you're on candid camera........



Huh!....Oh..oh.!.caught in action........



Ohhhh.....so......sweet........



OK! Everybody! Time's up! Stop smiling and start working.......

One drop...two drops...three drops....... Oh oh..no more already!



I think mine is overcooked...How about yours? Oh!...mine is well done!



Hemmm....how come mine is still dark blue.....???



Now...add saliva to the starch slowwwww...ly.......and..... stir fast!

Experiment 1: Measurement of cell size using microscope


Experiment 1 by L6ScBeta 2012

Light microscope was used in the experiment. What are the magnification of eyepiece and all the objective lenses?

The Lower Six Science Beta students were trying out the microscope.

The students were listening to the instructions given by the teacher.

HORMONES IN REPRODUCTION II

1.   Early pregnancy:
     -     trophoblastic cells secrete HCG
     -     which signals the corpus luteum
     -     to continue its secretion of oestrogen + progesterone.














2.   Later in pregnancy:
     -     secretion of oestrogen +  progesterone
     -     is taken over by the placenta.












 3.   Progesterone + oestrogen:
     -     develop + maintain endometrium (of the uterus)
     -     throughout pregnancy.
     -     ostrogen - promotes uterine contraction, while
     -     progesterone - inhibits it.

4.   In late pregnancy - ↑ oestrogen levels increase with respect to progesterone.

5.   Prior to birth:

     -     oxytocin stimulates uterine wall contractions
     -     causing the baby to be delivered.

6.   During pregnancy:

     -     the effect of prolactin (which promotes milk production)
     -     is inhibited by high levels of oestrogen + progesterone.

7.   After birth:

     -     When ↓ oestrogen + ↓ progesterone levels drop
     -     prolactin causes the breast to produce milk

8.   The interaction between hormones:
     -     oestrogen + oxytocin
     -     and local regulators (prostaglandins)
     -     induce + regulate labour.

 

9.   Oestrogens:
     -      which reach their highest level
     -     during the last weeks of pregnancy
     -     trigger the formation of oxytocin receptors on the uterus.

10.Oxytocin:

     -     stimulates powerful contractions of the uterus.
     -     also stimulates placenta to secrete prostagladins.

11.  Prostaglandins:

     -     enhance the contractions or the uterus,
     -     making them more powerful
     -      and more frequent.

12.  Physical + emotional stresses:

      -     in turn, stimulate the release of more oxytocin + prostaglandins.

13.  This positive feedback system à underlies the three stages of labour.

HORMONES IN REPRODUCTION I

1.   Menstrual cycle:

     -     lasts an average of 28 days
     -      controlled by the brain
     -      via hormones produced by the pituitary.

 

2.   Hypothalamus:
     -     produces GnRH
     -     which stimulates anterior pituitary
     -     to secrete FSH + LH into the blood.

3.   FSH:

     -     stimulates ovarian follicle growth
     -      which in turn secretes oestrogen.
     -      to stimulates the regrowth of the lining of uterus.

4.   Early in the cycle:

     -     low level of oestrogen ↓ à  inhibits secretion of FSH + LH  X.

5.   Middle of the cycle:

     -      high levels oestrogen ↑à stimulates a surge of FSH + LH ↑.
     -     surge of LH à triggers ovulation.
     -     ruptured follicle à develops into corpus luteum.
     -     corpus luteum à secretes oestrogen + progesterone.

 

6.   After ovulation:
     -          high levels of both oestrogen + progesterone levels to drop.

7.   At the end of the cycle:

     -     drop in ↓ oestrogen + progesterone blood levels
     -     causes uterine lining to disintegrate.
     -     frees pituitary from inhibition
     -     thus triggering the secretion of FSH + LH,
     -     which stimulates development of a new follicle.

8.   Menstrual cycle:

     -     refers to changes that occur in the uterus
     -     which begins with menstrual flow phase
     -     followed by proliferative phase,
     -     last phase - secretory phase.

9.   Ovarian cycle = running parallel to the menstrual cycle

     -     which begins with the follicular phase,
     -      followed by ovulation
     -     later, the luteal phase.

10.  Changes in the ovary + uterus:

      -     are correlated
      -     with the changing pituitary + ovarian hormone levels
      -   in menstrual cycle.

HORMONAL ACTION

1.   Hormones are molecules:
     -     produced by endocrine glands
     -     secreted into blood stream.
     -     transported all over the body
     -     act on target organs.

2.   2 groups of hormones (according to mode of action):

     -     steroid hormones
     -     peptide hormones

3.   Steroid hormones:

     -     eg: oestrogen, progesterone + testosterone
     -     derived from blood lipid cholesterol.
     -     are lipids
     -     so can enter cells easily
     -     by passing through phospholipids (part of plasma membrane).

 

4.   In cytoplasm:
     -     hormone binds to a protein receptor
     -     forms a hormone-receptor complex
     -     then moves into nucleus
     -     binds to specific region of the DNA.
     -     activates genetic transcription
     -     which produces mRNA
     -     then diffuses out of nucleus
     -     into cytoplasm
     -     binds to ribosomes
     -     translate into protein

 

5.   Peptide hormone:
     -     eg: adrenaline, glucagons + insulin.
     -     derived from amino acids.
     -     are polar (thus cannot enter cells easily)

6.   Peptide hormone:

     -     binds to the protein receptor (on the membrane)
     -     forming a hormone-receptor complex
     -     which then activates a membrane enzyme (adenylate cyclase).
     -     then catalyses the conversion of ATP to cAMP (2nd messenger).
     -     initiates a complex chain reaction (cascade effect)
     -     which simplifies response of the hormone.

NEUROMUSCULAR JUNCTION II

1.   Thick myosin filament:
     -     made up of myosin molecule.
     -     has a long tail + double head (projects from filament’s surface).
     -      head - contains ATP binding site.

2.   Thin actin filament made up of:
     -     two strands of globular actin protein (twisted together)
     -     regulatory proteins (troponin + tropomyosin).
3.   When Ca²⁺ is not available:
     -     troponin + tropomyosin - block myosin binding sites (on actin filaments).

4.   Muscular junction:
     -     specialised form of synapse
     -     found between motor neuron + sleletal muscle.
     -     spans across one unit of sarcomere.
5.   Sarcolemma = postsynaptic membrane
6.   Acetylcholine = transmitter substance (in synaptic vesicles).
7.    Acetylecholine binding sites = located in the folds of the sacrcolemma
8.   Calcium ions:
     -     found in abundance
     -     in sarcoplasmic reticulum.
9.   T tubules = very closely associated with sarcoplasmic reticulum.

10. Nervous impulse:
     è arriving at the neuromuscular junction
     è generates action potential
     è which spreads along sarcolemma.

11. Action potential:
     è depolarises T tubule
     è causing sarcoplasmic reticulum
     è to release Ca²⁺ ions
     è into sarcoplasm.
     è allow actin + myosin filaments to interact.

12. ATP:
     -     provides energy needed
     -     to power the sliding + pulling motion
     -     between actin + myosin.

13.  If Ca²⁺ ions + ATP conc. is sufficiently high à sequence will be repeated.