{SOMEWHERE OVER THE RAINBOW.}

Thursday, October 2, 2008

title:{Revision-2}

Continued frm previous...

*Chp7 - Nutrition in plants
-Photosynthesis->process in which light energyabsorbed by chlorohyll is transformed into chemical energy. The chemical energy is used to synthesis carbohydrates from water & carbon dioxide. Water & carbon dioxide are the raw material for photosynthesis. Oxygen is released during the process.
-De-starch a plant->put plant in darkness for abt 2 days
-If glucose forms more quickly then its used up, excess glucose is changed to starch for storage
-If photosynthesis has taken place, then glucose must be formed from CO2
-When testing leaf for starch, place leaf in boiling water to denature enyzme
-chlorophyll is a pigment in plants tt absorbs sunlight. It is green in colour.(thus leaf is green)
-Conditions for photosynthesis->Sunlight, CO2, chlorophyll, suitable temp & water
-Oxygen is given off during photosynthesis
-Limiting factors in photosynthesis->light intensity, concentration of carbon dioxide & temp.
-Glucose in leaves:
+cellular respiration, form cellulose cell walls
+excess is converted to sucrose, transported to storage organs
+In daylight, excess glucose is converted to starch in leaves, in darkness vice versa
+reacts with nitrates & other mineral salts absorbed from soil to form->amino acids->synthesis of new protoplasm/storage as proteins form proteins or synthesis of new protoplasm in leaves
+forms fats for storage/used in cellular respiration/synthesis of new protoplasm
-Stored food is digested & utilised
-Why is it impt?
+light energy is converted into chemical energy, organisms obtain it directly/indirectly
+removes carbon dioxide & provides oxygen tt is needed by organisms
+energy is stored in coal->used in cooking, vehicles, etc.
-Internal structure of the lamina(leaf)
+Upper epidermis-> top layer of lamina, covered by a waxy cuticle(protects leaf from excessive evaporation of water), no chloroplast
+Palisade mesophyll->numerous chloroplasts, most photosynthesis occurs here, long & cylindrical cells.
+Spongy mesophyll->irregular in shape, numerous intercellular air spaces among them for rapid diffusion of gas, contains chloroplasts, photosynthesises, all mesophyll cells haf thin flim of moisture around them for carbon dioxide to dissolve in it, vascular bundle present here
+Lower epidermis, similar to upper epidermis
+Stoma->minute openings, impt for gaseous exchange
+Guard cells->bean shaped, contains chloroplasts, can photosynthesis, control the rate of diffusion of gases into & out of the leaf by controlling size of stomata, has thicker cell wall near stomata
-How do Guard cells control size of stomata?
+when photosynthesis occurs, light energy is converted to chemical energy to pump potassium ions into guard cells via the epidermal cells, lowering the water potential. Water from neighbouring cells move into guard cell by osmosis so the guard cell becomes turgid
+at night, potassium ions diffuse out of guard cells, which increases water potential in the guard cells so water diffuse out by osmosis, guard cells become flaccid & stomata pores close
-How do CO2 & H2O enter the leaf?
+CO2 enters leaf via stomata when concentration of CO2 in the leaf is lower(during photosynthesis as its rapidly used up) than the surrounding, a diffusion gradient exists. Co2 dissolves into the thin film of moisture & diffuses into the cells as a solution
+The xylem transport water & mineral salts from the roots to the leaf.

*Chp8 - Transport in Humans
-Plasma->pale yellowish liquid, mixture of: (soluble proteins such as fibrinogen, prothrombin, antibodies, dissolved mineral salts, food substances, excretory products, hormones), transport all those substances along wif blood cells around the body.
-Red Blood Cells(RBC)->contains haemoglobin which combines reversibly wif oxygen, circulr biconcave disc which increases surface area to volume ratio, absorb & release O2 at a faster rate, do not haf a nucleus so it can contain more haemoglobin, elastic & can turn bell shaped to squeeze through blood vessels smaller then itself
-White Blood Cells(WBC)->larger than RBCs but fewer, colourless, no haemoglobin, irregular in shape, wif nucleus, can move & change its shape & squeeze through walls of thinnest blood capillaries into the spaces among tissues cells
+Lymphocyte->produced by bone marrow,large rounded nucleus, non-granlar cytoplasm, produce antibodies
+Phagocyte-> ingests & digests foreign particles such as bacteria, lobed nucleus & granular cytoplasm
-Blood platelets->Play a part in blood clotting

Arhh!!! Only at chp 8!! Still got alot le! Forget it, its late now, its like 11.01pm lo!!! So sleepyy, dun feel like typing le, 2moro got exam, so muz sleep now!! okays, bb!

A lollipop a day, keeps my sorrows away...

8:25 PM;