A-Level (Chemistry)

EQUILIBRIUM

-----> A mixture of products and reactants is formed.The product react together to re-form reactants at the same time as the reactants are forming products. (Reversible)

The characteristics of Equilibrium :

- It is dynamic
-The forward and reverse reactions occur at the same rate.
-The concentrations of reactants and products remain constant at equlibrium.
- It requires a closed system .

A-Level (Biology)

Blood Plasma And Tissue fluid.

Plasma : Cells floating in a pale yellow liquid.

Tissue Fluid : the colorless fluid that fills the spaces between body cells.

-Blood : Handles the distribution of nutrients, O2 and Hormones.

-Arteries and Veins : Form the transport route where blood flows à made up of 3 layers ,such as :

1) Inner layer ( Endothelium)

2) Middle layer (Tunica media)

3) Outer layer (Tunica externa)

-Heart : The motor of this transport service.

Capillaries : are sites of exchange.

Blood  :

1)      White  Blood : Made in the bone marrow but are easy to distinguish from red blood cells

2)      Red Blood        : Transport oxygen from lungs to respiring tissues.

Transport in multicellular plants

WHY PLANTS & ANIMALS NEED A TRANSPORT SYSTEM ????
------> to carry these items and other necessities throughout the body to cells that would not be able to get it from the air. In plants the transport systems are xylem and phloem, and in animals it is the circulatory system.



Some of the particular requirements of plant cells are as follows :

- Carbon dioxide : Photosynthetic plant cells require a supply of CO2 during daylight
- Oxygen             : All plant cells require a supply of oxygen for respiration
- Organic nutrients : Many plant cells need to be supplied with organic nutrients
- Inorganic ions& water : These are taken up from the soil by roots & are transported to all regions of the plant.

(transport in plants )

The transport of water

-The energy of the Sun causes water to evaporate from the leaves called TRANSPIRATION

THE STRUCTURE OF XYLEM & PHLOEM

Difference and Comparison

Phloem and xylem are complex tissues that perform transportation of food and water in a plant. They are the vascular tissues of the plant and together form vascular bundles. They work together as a unit to bring about effectivetransportation of food, nutrients, minerals and water.

PHLOEM	XYLEM
Transportation of food and nutrients such as sugar and amino acids from leaves to storage organs and growing parts of plant	Water and mineral transport from roots to aerial parts of the plant.
Nature of tissue : Living tissue with little cytoplasm but no nucleus/tonoplast.	NOT : Dead tissue at maturity so it is hollow with no cell contents
Location in vascular bundle : Phloem occur on outer side of the vascular bundle.	xylem occupy the center of the vascular bundle.
Shape : Phloem is not star shaped.	Xylem is star shaped.

THE ROLES OF NITRATE & MAGNESIUM IONS IN PLANTS

- Nitrates provide the nitrogen plants need to construct such vital molecules as amino acids and nucleic acids (DNA and RNA). Also some of the vitamins. Lack of nitrates means stunted growth, low yields, yellow leaves. 

- Magnesium is the ion that's vital to chlorophyl function and photosynthesis. Without it leaves turn yellowish and/or red orange in colour, shrivel and die.

HOW TRANSLOCATION OF ORGANIC MATERIALS OCCURS IN PLANTS

Translocation involves the transport of organic materials produced through photosynthesis, such as sucrose, from the leaves to other parts of the plants where they are utilized. It occurs in the phloem sieve tube between the source end(near the leaves); where sucrose is loaded due to the process of photosynthesis by the palisade and spongy mesophyll cells to the sink end(near the end where sucrose is unloaded for respiration and storage purposes).

Cell membranes and Transport

Phospholipids
A substance whose molecules are made up of a glycerol molecule , two fatty acids and a phosphate group; a bilayer of phospholipids forms the basic structure of all cell membranes. Interestingly,when a phospholipid is placed in water, it spontaneously folds upon itself to create a double layer or bilayer.


Here are some examples of Phosholipids in water
a. Spread as a singgle layer of molecules( a monolayer) on the surface of water

b. Forming micelles surrounded by water

c. Forming bilayers

d. Bilayers forming membrane-bound compartments

Structure Of Membrane

Membranes have many different functions with a typical cell, such as keeping unwanted viruses out, buht probably the most valuable is the partitioning of the cell into the functional and segregated compartments.

This is the diagram of the fluid mosaic model of membrane structure.

The Roles of the domponents of cell membranes

1. Phospholipids : This is the basic structure of membrane .They act as barrier to most water-soluble molecules such as sugars,amino acids & proteins cannot leak out of the cell, and unwanted water soluble molecules cannot enter the cell.

2.  Cholesterol : Is a relatively small molecule ,the function is they fit neatly between the phospholipid molecules with their heads at the membrane surface.

3. Glycolipids, glycoproteins and proteins : They form hydrogen bonds with the water molecules and help to stabilise the membrane structure.

Transport across the cell surface membrane 

There are 5 basic mechanisms by which this exchange is achieved : Diffusion, Facilitated diffusion, Osmosis , Active transport and bulk transport.

A. Diffusion : can be defined as the net movement, as a result of  random motion of its molecules or ions, of a substance from a region from its higher concentration to a region of its lower concentration.

A substance diffuses across a membrane depends on a factors , such as :

1.The 'steepness' of the concentration gradient.

2. Temperature

3. The surface area

4. The nature of the molecules or ions 

B. Facilitated Diffusion : It can only cross the membrane with the help of certain protein molecules.Facilitate means to make easy or make possible and this is what the proteins do.

C. Osmosis : is the best regarded as special type of diffusion involving water molecules only.

D. Active transport :as the energy consuming transport of molecules or ions across a membrane against a concentration gradient.

E. Bulk transport :  There are two type of it which is :

1. Endocytosis : engulfing of the material by the cell surface membrane to form a small sac or 'endocytic vacuole' it takes to forms ,they are Phagocytosis (cell eating) and Pinocytosis (cell drinking).

2. Exocytosis : is the process by which materials are removed from cells.

-This is an assignment for my Biology A level-

By : Via noviani

Ethanol emulsion for testing of fats

Materials :                                                                                               

- Ethanol                                                                                                

- Sticky rice (Lontong)                                                                            

- Brownies                                                                                              

- Rice                                                                                                      

- Coconut oil                                                                                           

- Alcohol                                                                                                 

- Bread

Equipments :
 - Test tube
- Filter funnel
- Mortar & Pestle

- Stiring rod
- Test tube rack
- Filter paper

Preparation of a solid sample :

1. Completely crushes adequate amount of food with a clean and dry mortar and pestle.

2. Transfer an adequate amount of crushed food sample to a clean test tube

3. Adds 2cm ethanol above the food sample

4. Shakes the test tube thoroughly and safely .

5. Allows the solid to settle for about 3 min

6. Decants the ethanol carefully into a clean,dry test tube without transference of food particles.

7. Adds 2cm of de-ionized water to the test tube

8. Compares each result with the negative control

9. Compares the heights of the emulsion layer of all the samples

Process

• Add the food sample to 2 cm3 of ethanol, shake well.
• Allow to settle in a test tube rack for 2 minutes for food to dissolve in ethanol.
• Empty any clear liquid into a test tube containing 2 cm3 of distilled H2O.
• A MILKY-WHITE EMULSION is a positive result: lipid is present.
• If the mixture remains clear, there are no fats present in the sample

Substance tested	Presence of spot	Lipids presence ?
Brownies	Yes	Yes
Rice
Sticky rice
Cooking oil	yes	Yes
White bread	Yes
Whole bread	No	No

By : Via Noviani { year 11}

Testing starch in foods

By : Via Noviani

The Presence Of Starch

Starch : An odorless tasteless white substance occuring widely in plant tissue and obtained chiefly from cereals and potatoes. It is polysaccharide that functions as a carbohydrate store and is an important constituent of the human diet.

Equipments :                                                        Materials :
                                                         
- Evaporating dish                                               - Iodine solution  I₂
- Test tube                                                         - Grape Juice
- Test tube rack                                                  - Banana
- Fume hood                                                      - Potato
- Filter funnel
- Knife
- Pestle/mortar
- Glass rod
- Pipette
- Tongs
- Bunsen burner
- Breaker


Steps :
1. Divide the banana into two ,add 3 drops of Iodine solution
2. Divide the potato into two ,add 3 drops of Iodine solution
3. Put the grape juice into test tube ,add 3 drops of Iodine solution
4. Do all those things inside the fume hood
5. You can see the result

In order to perform this project, we must use Iodine solution as a reagent for starch. One drop of this solution on any sample can detect starch by changing the color of the tested area to dark blue.We will be using the following samples :

SAMPLE	NORMAL COLOR	ADDED BY IODINE SOLUTION
Banana	Cream	Black
Potato	Cream	Black
Grape Juice	Purple	No changes

( This is an assignment for my Biology A Level  )

Starch Indicator : A blue-black color indicates the presence of starch. The darker the color ,the greater starch it's contain.

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This is an assignment for my A Level Class =D

North Borneo Railway

Last year, I, as a travel writer, went to Borneo.I used a train to Borneo through North Borneo Railway . I was very interested in travelling  but much disappointed because of the bad services at the local station. There was no time table shown and I was uncertain what time I can go back to find a famous place and I couldn't enjoy my travel . It was actually a vintage train and I didn't know whether it was comfortable or not.The facilities were not completed yet , no air conditioner, it was rickety and also the food were less tasty. I prefered not to eat the food , I'd rather starved than to eat those odd foods. The journey made me so dizzy. I was not physically fit and in the end I threw up. So,when you are going to visit Borneo and use the North Borneo Railway , you should bring plenty of plastics and bring lots of food.

  I thought this would be the best time in my life, apparently it was not .This experience must have a historical value and I believe it is inappropriate for travelers who are not ready for the condition.

This is an assignment for my A level class : D

Enzymes

Enzymes  are large biological molecules responsible for the thousands of chemical interconversions that sustain life. They are highly selective catalysts, greatly accelerating both the rate and specificity of metabolic reactions, from the digestion of food to the synthesis of DNA. Most enzymes are proteins, although some catalytic RNA molecules have been identified. Enzymes adopt a specificthree-dimensional structure, and may employ organic (e.g. biotin) and inorganic (e.g. magnesium ion) cofactors to assist in catalysis.

Enzyme activity can be affected by other molecules. Inhibitors are molecules that decrease enzyme activity; activators are molecules that increase activity. Many drugs and poisons are enzyme inhibitors. Activity is also affected by temperature, pressure, chemical environment (e.g., pH), and the concentration of substrate. Some enzymes are used commercially, for example, in the synthesis of antibiotics. In addition, some household products use enzymes to speed up biochemical reactions (e.g., enzymes in biological washing powders break down protein or fat stains on clothes; enzymes in meat tenderizers break down proteins into smaller molecules, making the meat easier to chew).

The Other Benefit Of Enzymes

Polar and Non-Polar Molecules

Molecules can be grouped as polar or non-polar molecules. Some are also in between.

The arrangement or geometry of the atoms in some molecules is such that one end of the molecule has a positive electrical charge and the other side has a negative charge. If this is the case, the molecule is called a polar molecule, meaning that it has electrical poles. Otherwise, it is called a non-polar molecule.

Whether molecules are polar or non-polar determines if they will mix to form a solution or that they don't mix well together. Also, polar molecules are water soluble, while non-polar molecules are fat soluble.

Questions you may have include:

• What is a polar molecule?
• What is an example of a non-polar molecule?
• What rule is there to determine if substances will form solutions?

This lesson will answer those questions.

Polar molecules

Chemical bonding is the result of either an atom sharing one or more outer orbit electrons with another atom or an atom taking outer orbit electrons from the atom with which it is bonding. Normally, an atom has an even distribution of electrons in the orbits or shells, but if more end up on one side that the other in a molecule, there can be a resulting electrical field in that area.

Water is polar

Water is a polar molecule because of the way the atoms bind in the molecule such that there are excess electrons on the Oxygen side and a lack or excess of positive charges on the Hydrogen side of the molecule.

Water is a polar molecule with positive charges
on one side and negative on the other

Examples of polar molecules

Examples of polar molecules of materials that are gases under standard conditions are:

• Ammonia (NH₃)
• Sulfur Dioxide (SO₂)
• Hydrogen Sulfide (H₂S).

Also, Ethanol is polar, since its oxygen molecule draws electrons towards it due to its high electro-negativity, causing a negative charge around itself.

Non-polar molecules

A non-polar molecule is one that the electrons are distributed more symmetrically and thus does not have an abundance of charges at the opposite sides. The charges all cancel out each other.

The electrical charges in non-polar Carbon Dioxide are evenly distributed

Examples of non-polar liquids

Most hydrocarbon liquids are non-polar molecules. Examples include:

• Toluene
• Gasoline

Alkynes are non-polar because they cannot be dissolved in water, as do polar molecules. However, alkynes but do dissolve in other non-polar substances. A rule is that like substances dissolve in like substances.

Examples of non-polar gases

Common examples of non-polar gases are the noble or inert gases, including:

• Helium (He)
• Neon (Ne)
• Krypton (Kr)
• Xenon (Xe)

Other non-polar gases include:

• Hydrogen (H₂)
• Nitrogen (N₂)
• Oxygen (O₂)
• Carbon Dioxide (CO₂)
• Methane (CH₄)
• Ethylene (C₂H₄)

Since Chloroform is more soluble in fats than in water, it is also classified as non-polar.