imagine the line at the centre of the graph is the optimum condition, the wiggly line shows temperature rising and falling, but negative feedback means the level always returns to normal.
in positive feedback, the level doesnt return to normal, but continues to travel away normal.
Homeostasis uses negative feedback.
Negative feedback detects a change then brings levels back to normal. So when internal temperature rises, homeostasis uses negative feedback to return levels to normal.
Positive feedback does the opposite. It amplifies levels above normal.
It’s used to rapidly activate something. A example of positive feedback in a useful way is to create a blood clot:
however, positive feedback can also be bad:
Positive feedback is NOT used in homeostasis.
so jack got too cold, enzymes couldn’t function properly, metabolic reactions slowed to a stop and he froze to death.
homeostasis saves lives, guys.
homeostasis is the maintenance of a constant internal environment.
This is within certain limits though, so if your internal body temperature is only 0.5°C above/below it’s optimum temperature (37°C in humans) then it wont be such a problem. However if your temperature were to rise to something like 40°C, or drop to 33°C, your body would have to act in order to survive.
So putting it simply you respond to your internal and external environment in order to survive, so homeostasis is important.
Homeostasis involves receptors, communication systems and effectors:
EFFECTORS effect the body by counteracting the change, and bringing levels back to normal.
effectors can be muscle cells or cells in glands.
A change in your external environment can affect your internal environment, keeping a constant internal environment keeps us alive.
So going back to the temperature example:
Optimum conditions for enzymes are important because enzymes control the rate of metabolic reactions (chemical reactions within your body). If your enzymes don’t function properly and you need something within you to react quickly and it doesn’t it can become fatal in extreme situations.
For example, if your body temperature dropped and you couldn’t bring it back to normal, you would be more likely to become ill.
Glucose concentration is also important as you will always need enough available for respiration.
been a long time since i’ve actually posted on here, but with january here and exams on the horizon, i’m revising for OCR F214 module. however im sure that the syllabuses overlap and hence some aspects will (hopefully be useful to others :))
starting off with homeostasis (hence the big cheesy picure ;)) but will switch between other subjects so if you’re lost just hit search, type a word and hopefully it should appear (eventually). if not then ask and i’ll see what i can do :)
Some youtube clips worth having a look at - for anyone studying biology, chemistry, maths or physics at AS level. Good stuff, fun to watch (except the torture of watching someone else eat a delicious cupcake when you sit at home wishing you had one ;)) and broken down so is easy to get - from the clips i’ve seen, not a great fan of maths so kinda avoided that one :p - so all in all worth checking out :)
http://www.youtube.com/user/smartledore?feature=results_main
Anonymous asked: what is crossing over
the crossing over of chromatids is when two chromatids (one from the mother and one from the father) twist around eachother and snap off, joining the opposite chromatid. so in other words part of the mother’s dna joins onto the fathers, creating genetic variation :)
for more info go onto the search link and type in ‘crossing over’ for diagrams and more detail :)
diagram demonstrating how you can identify the desired gene using marker genes - in a nutshell it makes it so either only the transformed gene survives, or only the transformed gene is visable (using UV light)
Anonymous asked: What is the use of generic marers and how do we use them to identify clls that contain recombinant plasmids?
marker genes/genetic markers (i take it that’s what you mean) are used to identify the desired gene that is inserted into the vector (such as a plasmid or bacteriophage).
genetic markers are inserted into the vector at the same time the desired gene is, so if you’re using bacteria as a vector, as the bacteria grows the transformed cells (the ones with recombinant DNA) will produce more and more cells with the markers and desired genes in.
There are two ways of identifying the genes using the markers:
1) the marker gene codes for florescence meaning when held under a UV light, only the transformed cells containing the marker (and therefore desired gene) will show (will fluoresce)
2) the marker gene codes for anitbiotic resistance, meaning all the non-transformed cells won’t survive and only the transformed cells are left.
hope this explains what you needed ok :)
couldnt find many helpful sites so decided to make my own, mostly cos writing/creating things helps me revise, hopefully it'll help some others too :)
if you're looking for something in particular, click search and see if you can find it (type in a keyword for a particular topic eg. type DNA and genes, mutations, development and other relevant topics, definitions or diagrams should come up), otherwise message me - no guarantee i'll be able to find it, i am a student, not the oracle ;)
