biology

Right eye is sore and bothering me. Miss Ting has long feet. My rabbit is horny. It wants to mate with the cloth. There's a bio test tomorrow, E maths test the day after, and a POA test on thursday. Have to submit the class outing proposal to Miss Chan for the sec 1s' class outing by Friday. Peer lites meeting with mentors on Saturday, then my group will go to old folks' home, orphanage or childcare centre to do some stuff. I can't go, must go for worship prac and it's quite important cos of Sunday. About the Julia and Nisa thing, we still haven't tell any of the teachers, I'm prepared to get a lecture from Miss Kok and Mrs Soh. I want to watch I Not Stupid Too. I am deprived of TV. Don't even know what 'snuppy' or whatever it is about. I want to go for the Symposium!!!! But no money, so can't even think about it. Sharon amswered all the questions during SS today, unfair! Grace is so pink. Hyun bin, wahahaha.

RIGHT. Those were totally RANDOM stuff. Let's get on with a biology lesson.

Enzymes
*biological catalysts made up of protein.
*molecules that speed up reactions without themselves being chemically changed.
*produced by living cells.

Digestion is the breaking up of large, insoluble, indiffusible molecules into smaller, simpler, diffusible molecules.

Hydrogen peroxide is sometimes released during chemical reactions.
It is poisonous!
-the cell produces enzyme catalase which catalyses the breakdown of hydrogen peroxide into water and oxygen
-in this way, the toxic effect is prevented.

Classification of Enzymes
- Digestion is an example of a chemical reaction called HYDROLYSIS.
--- using water to speed up/water splitting.
--water molecules are needed to break down a comples molecule into simpler molecules.
.:. Enzymes that catalyse hydrolytic reactions are known as HYDROLASES
-Examples of hydrolases:
--Carbohydrases
*amylase (salivary/pancreatic) which digest or hydrolase starch.
*cellulases which digest cellulose. Not produced in mammals, that's why animals cannot digest cellulase.
--Proteases (Pepsin in the stomach pH2, Trypsin in the small intestine pH9)which digest proteins.
--Lipases which digests fats (lipids)
-Digestive enzymes are used in some washing powders!

Characteristics of enzymes
-they speed up chemical reactions w/o being changed.
-they are required in small amounts
-they are highly specific in their actions
--e.g amylase will only act on starch, not proteins or fats.
--action of enzymes illustrated using the LOCK AND KEY hypothesis
----the enzyme (lock) has an active site that is of a spatial configuration.
----Only a specific substrate can bind to the active site of the enzyme.
----Only substances that can complement the shape of the active site can be broken down.
-Effect of temperature
--inactive at low temperature, 0°C to 30°C
--temperature ↑, activity ↑
--enzyme twice as active for every 10°C rise until the optumum temp is reached (40°C to 48°C for most enzymes)
--enzyme denatures beyond the optimum temperature.
WHY DO ENZYMES BECOME DENATURED??
because i want them to
because, Too high temp will destroy the protein nature of the enzyme.
- effect of pH on enzymes
--enzymes are very sensitive to pH.
--can only work within a narrow range.
--choose the narrowest optimum pH thing in MCQ.
-Effects of substrate and enzyme concentrations on rate of reaction
--(refer to page 41 of TB, fig 4.4) As the substrate concentration increases, the rate of reaction increases initially until point X is reached. A further increase in substrate concentration does not increase the rate any further. This is because, at any given instant, all the enzyme molecules are being saturated or made used of. The amount of products formed per unit time is the same.
WHAT IS A LIMITING FACTOR??
it is any factor that directly affects the rate at which a process, such as a chemical reaction occurs if quantity is changed.
HOW CAN YOU INCREASE THE RATE OF REACTION AT POINT X?
Increase the enzyme concentration la!

Some stuff on diffusion and osmosis.

The stem curls outwards, with the cortex cells expanding more than epidermal cells.
This is caused by the turgor pressure in the cortex cells.
Cortex cells prevented fom expanding be the epidermis layer, made up of epidermal cells.
They are held by a cuticle and so less capable of stretching.
The cuticle also protects the epidermal cells against water loss.
Cutting releases the restraintexerted by the epidermis.

Sitll have a lot, I'm not typing anymore. Time is 11.35pm