Biology Unit 3 Questions Megathread

[HERculina]

douchy explained it as hormones being secreted directly into the bloodstream and not into a tube.
duct = 'to lead'

EXOCRINE glands for example produce products delivered through tubes called 'ducts'

EDIT: go to  http://answers.yahoo.com/question/index?qid=20080722100846AAz9qFt

[shinny]

These organ ducts are also quite large structures - when Russ says channels, he doesn't just mean like an ion channel or something. Some are easily anatomically visible such as the biliary tree (connecting the liver, gallbladder and pancreas to the intestines), while others such as the tear ducts, mammary ducts and so on are a bit smaller. But basically, they're tubes lined by cells leading from one organ to another or to the surface.

[Kaille]

can someone please explain the action of gravity and auxin on root cells? i'm not really understand it

Auxin inhibits cell growth in roots. Therefore when auxin settles on the lower side of the root, cell growth is inhibited. However, the uppermost side of the root is still able to growth, resulting in the bending of the root towards gravity.

[WhoTookMyUsername]

Thankyou,

so does that mean hormones are secreted via normal cellular processes such as exocytosis, active transport, faciliated diffusion and diffusion?

Also, what exactly does humoral mean?
In terms of
a) immunity and
b) Describing homeostatic mechanisms such as Blood Glucose control


Edit: Are non - metallic ions such as chlorine minerals?

Edit 2: As trophic refers to the Carbon Source, why are prions and viruses 'non - trophic' if they get carbon from other organisms?

Edit 3: Can amino acids and glucose pass through the phospholipid bilayer by simple diffusion? Or are they too big / too polar

Edit 4: Are CAM plants C4 or C3, Neap says C4, teacher said C3

[Kaille]

Heinemann says that amino acids and simple sugars pass through protein channels. but insight 2007 exam says otherwise. i'm assuming you have already done that exam?

[Kaille]

also is there such thing as a "diuretic hormone"? or is less adh produced to combat a high water conc. in the blood?

[WhoTookMyUsername]

less adh is used

[shinny]

so does that mean hormones are secreted via normal cellular processes such as exocytosis, active transport, faciliated diffusion and diffusion?

Mainly exocytosis as far as I know. Hence the need for large golgi and many mitochondria in most cases.

Also, what exactly does humoral mean?

Relating to the blood. So for immunity it refers to the antibody-based defenses rather than the cellular based ones. As for homeostasis, any mechanism which operates through the blood in some way.

also is there such thing as a "diuretic hormone"? or is less adh produced to combat a high water conc. in the blood?

Well there is atrial natriuretic peptide released by the heart, but it's not something you need to worry about. ADH is the main factor involved.

[Russ]

The entire blood pressure regulation thing is a nightmare of acronyms

[shinny]

The entire blood pressure regulation thing is a nightmare of acronyms

The hypothalamic-pituitary axis definitely takes the cake. TRH, GHRH, GnRH, CRH, ACTH, TSH, GH, LH, FSH, PRL to name a couple...

[Russ]

I have repressed the hypothalamus from my memory of physiology and that's the way it should stay

[Kaille]

How can you reason whether an experiment has a control or not? For example, in an experiment with an egg in distilled water, an egg in a sucrose solution and an egg in an isotonic solution could you reason that the egg in the isotonic solution is the control (assuming that all other variables are kept constant)?

[Russ]

The control is whichever experiment where the variable you're altering (tonicity) will not affect the variable you're measuring. A pure water solution or a pure sugar pill (for drug testing) is not always an appropriate placebo because it may have an effect

[HERculina]

Are CAM plants C4 or C3, Neap says C4, teacher said C3

i would say neither.
but since it was a question i think neap is right. CAM plants like C4 plants, form a 4-compound carbon ('malate' or 'malic acid') before it fixes it into a triose sugar. the only difference is that C4 plants transport this 4-carbon compound into the bundle sheath cells to be fixed whereas CAM plants store it overnight to be used in the calvin cycle during daytime (in the same mesophyll cells, not bundled-sheath cells). 
but i also know that during rainfall CAM plants can convert back to the C3 pathway (maybe this is why your teacher thought they were more C3?)

Can amino acids and glucose pass through the phospholipid bilayer by simple diffusion? Or are they too big / too polar

I don't think so?
look at the diagram attached
 

[Kaille]

The control is whichever experiment where the variable you're altering (tonicity) will not affect the variable you're measuring. A pure water solution or a pure sugar pill (for drug testing) is not always an appropriate placebo because it may have an effect

so the egg placed in the isotonic solution has no effect on the variable (ie. increase or decrease in weight) and thus can be deemed a control?