BIOLOGY FORM 6

U6scZeta Rat Dissection 2012

2012-03-06T12:34:00.004+08:00

Here kitty kitty... here kitty kitty... nice kitty...!

Here....take it ...make sure its properly cooked!

Here you are....this is a big one... specially kept.. for U!

Like this....massage here...and a little bit there...that's the way!

Help!!!.. I'm stucked!!!...

Yes...snip snip here....and... snip snip there....!

Oh no... not there! It's tickling there.....haha..hoho..haha....

Help!...I've been violated!!!!

Parade of maidens with their presentation on... rat dissection!

Sorry!.. you have been exposed........

Now... I know... the rubbish inside you.....!

Homeostasis ll

2011-11-06T21:55:00.005+08:00

1. The pancreas

- functions as exocrine + endocrine gland.

- has 2 groups of cell in the pancreas.

- α & β-cells in the islet of Langerhans play (major role in blood glucose concdntration).

- α-cells - secrete glucagons

- β-cells - secrete insulin into blood capillaries.

α & β-cells in the islet of Langerhans

2. Blood glucose level rises↑à due to carbohydrate breakdown.

3. Insulin + glucagons have opposite effects.

4. Insulin:

- secreted by β-cells (when glucose↑ level increases).

- target organs = liver + muscle tissues.

- convert glucose à to glycogen.

5. Glucagon:

- secreted by α-cells (when the glucose↓ level decreases)

- Target organ = liver cells.

- convert glycogen à glucose.

Pancreas response to different level of glucose

6. Ingestion of glucose à increase insulin level ↑.

7. 2 types of diabetes: Type I & Type II.

Blood glucose & insulin level in normal & diabetic person.

8. Formation of tissues fluid is a physical process.

9. At arteriol end:

- smaller blood plasma content is forced out

- when hydrostatic pressure (HP) > osmotic pressure (OP).

10. At venous end:

- tissue fluid re-enters capillary

- when osmotic pressure (OP) > hydrostatic pressure (HP).

Homeostasis

2011-10-24T01:45:00.014+08:00

1. Homeostasis

- maintenance of internal environment within cells (tissue fluid + blood plasma).

- has 3 functional components: receptor, control centre + effector.

- 2 types of mechanism:

a. Negative feedback.

b. Positive feedback.

- 2 types of animals (that respond to the fluctuations in temperature): endotherms + ectotherms.

Ectotherms

Endotherms

2. To maintain a stable body temperature à organism needs to balance heat gain with heat loss.

3. Heat gained/lost thru:

- conduction,

- convection

- radiation,

- evaporation (heat lost only).

4. Ectotherms - exhibit behavioural thermoregulation.

5. Endotherms - show physiological + behavioural thermoregulation

6. Internal body temperature à sends impulses to hypothalamus (via blood vessels + afferent nerves respectively).

7. In thermoregulation:

- receptors (thermoreceptors) = nerves beneath the skin,

- control centre = hypothalamus

- effectors = sweat glands + blood capillaries (beneath skin).

Endotherms show physiological and behavioural thermoregulation

Ectotherms exhibit behavioural thermoregulation

Translocation in Plants

2011-10-05T01:06:00.017+08:00

(A) Mass-Flow/Pressure Flow Hypothesis:

1. The mass-flow/pressure flow hypothesis:

- postulates that dissolved sugar moves in phloem

- by mean of pressure gradient

- which exists between the source and sink.

2. The photosynthetic cells in:

- leaves = common source of sugars
- roots = sinks.

3. At the leaves

- sucrose is actively transported

- from mesophyll cells

- to companion cell

- into sieve tube

- against its concentration gradient

- process = phloem loading.

- high conc of sucrose↑ à lowers cell water potential (Ψ_w)↓.

- water - drawn into sieve tube

- from nearby xylem vessel

- creating a high hydrostatic pressure (HP)↑

- forces the bulk/mass flow of the phloem sap

- towards the sink.

Phloem loading and unloading of sucrose

4. At the root:

- sucrose is actively transported

- from the sieve tube

- into the companion cell

- into a root cell.

- process = phloem unloading.

5. Loading (at the source) and unloading of sugar (at the sink)

- require energy derived from ATP.

(B) In Electro-Osmosis Mechanism:

potential diff develops across sieve plate
by companion cell (actively transport K⁺ into sieve tube).
K⁺ accumulate at one end of sieve plate
creates a potential diff between sieve plate.
caused K⁺ speed across sieve plate
water + dissolved sucrose follow (attracted by +ve charge).
water in phloem moves by osmosis
as accumulation of K⁺ lower Ψ_w in sieve tube (compared to next cell).

K⁺ accumulate at one end of sieve plate creates a potential diff between sieve plate

(C) In Cytoplasmic Streaming Mechanism:

water + dissolved compounds (in phloem sap)
move + circulate together
in one direction (in sieve tube)
it’s slow + depends on metabolic energy/due to their kinetic energy.
circulation slow down at sieve plate
and forced out from cytoplasmicc streaming (thru pores)
to cytoplasmic streaming of next sieve tube.

Circulation slow down at sieve plate

(D) In Peristaltic Wave Mechanism:

sieve tube is filled with fine cytoplasmic filaments
continuous from sieve tube to the next
thru pores of sieve plate.
contain phloem sap tube constrict + relax alternately
pushing sap from one sieve tube to the next.
constriction + relaxation/peristaltic movement form a pattern of wave = peristaltic wave
can be at diff speed + in opposite direction (in sieve tube)
depends on metabolic energy/ATP.

Phloem sap tube constrict + relax alternately

Macromolecules across the plasma membrane

2011-09-18T11:07:00.001+08:00

http://www.slideshare.net/contactmeasif/transport-of-macromolecules-across-cellmembrane

Transport of Water: Mechanism

2011-09-12T02:37:00.008+08:00

1. Two theories to explain water + minerals transport in plants

- root pressure theory

- cohesion-tension theory.

2. Root-pressure theory:

- accumulation of mineral ions in the xylem

- enhances water molecules to move into root hairs (by osmosis).

- water pressure ↑ builds up in the root

- pressure pushes up water + dissolved minerals

- through the xlem

- toward the top of the plant.

- but not strong enough to push up water to the top of tall trees.

Root pressure

3. In small plants:

- root pressure can build high enough

- to force water and minerals completely out of the tips of the leaves

- the process = guttation.

4. Cohesion-tension theory suggests that:

- water inside the xylem is pulled upward

- by the -ve pressure (or tension)

- that extends all the way from leaves to roots.

5. In the leaf xylem:

- -ve pressure (tension) builds

- as water evaporates during transpiration.

- evaporated water is continually replaced

- thus cohesive bond pull the string of water molecules up

- to create a transpiration pull.

- transpiration pull is relayed

- molecule by molecule

- down the entire column of water in the xylem.

Transpirational pull in the leaf

6. In the stem, water molecules:

- exist as a long unbroken chain in the xylem.

- are pulled upwards by tensions produced (during transpiration).

- are held by cohesion + adhesion forces

Cohesion and adhesion forces in the xylem

7. Transpiration pull:

- can extend down to the roots

- only through an unbroken chain of water molecules.

8. At the cellular level:

- the gradients of water potential

- drive the osmostic movement of water

- from cell to cell

- within the roots up to the leaves.

Water potential in leaf, stem and root

Transport of Water: Concept

2011-09-12T01:27:00.007+08:00

1. Dissolved substances (inside a plant cell) = contribute to solute potential (ψ_s).

2. More solute molecules present --> the lower is the water potential (ψ).

3. When water pontential is lower than> external solution:

- water molecules move into the cell .

- pressure inside the cell increases

- sell contents press against the cell wall

- create a pressure potential (ψ_s).

4. Water potential (of a plant cell) = solute potential + pressure potential.

5. Water potential = free energy of water.

6. By convention, water potential of pure water = 0 megapascal (MPa).

7. Water will move:

- from a region of higher (less -ve) water potential

- to a region of lower (more -ve) water potential.

8. In plasmolysed cell:

- pressure potential = zero

- water potential = solute potential.

9. As more water molecules enter a cell

- pressure potential ↑ increases

- so is its water potential ↑

- cell becomes turgid.

- less and less water molecules enter the cell.

10. Most minerals

- are actively transported into the root.

- there is a gradient of successfully

- lower water potentials from root hair to the xylem vessels

- result in water uptake by osmosis is enhanced.

11. Water moves by osmosis in the roots follows three pathways:

- apoplast

- symplast

- vacuole.

12. Apoplastic pathway:

- water travels along the cell wall

- and extracelular spaces.

Apoplast pathway

13. Symplastic pathway:

- water moves across the cytoplasm of one cell to the next

- across the plasma membrane

- through the plasmodesmata.

Symplast pathway

14. Vacuole pathway:

- water moves from vacuole to vacuole of one cell to the next

- across the plasma membrane

- through the plasmodesmata.

Vacuole pathway

Cardiac cycle

2011-07-19T22:17:00.000+08:00

Cardiac Cycle

2011-07-19T01:38:00.003+08:00

1. Heart contracts + relaxes in a rhythmic cycle.

2. Cardiac cycle consists of alternating periods of :

· Systole - contraction phase.

· Diastole - relaxation phase.

3. Cardiac cycle = one complete sequence of systole + diastole

4. Resting adult - cardiac cycle repeated 72 times per minute = resting heart rate.

5. Pulse = causes by elastic recoil of arteries.

6. Ventricular pressure + aortic pressure + ventricular volume:

changes (in response to the events that occur)
at different phases of cardiac cycle.

7. During diastole:

pressure↓of heart chambers decreases
volume↑ increases (as blood is pumped in).

8. During systole:

pressure↑of heart chambers increases
volume↓ decreases (as blood is pumped out).

9. When aortic pressure > ventricular pressure

à semilunar valves shut + vice versa.

10. When ventricular pressure > atrial pressure

à AV valves shut + vice versa.

11. Valves = ensure blood only flows in right direction.

Transport In Animals

2011-07-12T11:47:00.013+08:00

1. Human heart :

consists of 4 chambers : right atrium, right ventricle, left atrium and left ventricle.
pump blood to all parts of the body.
made up of cardiac muscle.

Front/venrtral view of heart

2. Superior vena cava
    --> carries deoxygenated blood
    --> from the head + arms
    --> into right atrium.

3. Inferior vena cava
    --> carries deoxygenated blood
    --> from the lower body + legs
    --> into right atrium

4. Right atrium
    --> receives deoxygenated blood
    --> from vena cava
    --> to right ventricle.

5. Tricuspid (antrioventricular) valves
--> prevent blood (from right ventricle) flowing backwards
--> to the right atrium.

6. Right ventricle
    --> pumps blood
    --> to lungs
    --> via pulmonary arteries.

7. Semilunar valves
    --> prevent blood (from pulmonary arteries)
    --> from flowing backwards
    --> into right ventricle.

Cross-section of heart

8.   Pulmonary artery branches
      --> carries deoxygenated blood
     --> from right ventricle
      --> to lungs.

9.   Pulmonary vein
      --> carrying oxygenated blood
      --> from lungs
      --> to left atrium.

10. Left atrium
      --> receives oxygenated blood
     --> from lungs
      --> to left ventricle.

11. Bicuspid (atrioventicular) valves
-- > prevent blood (from left ventricle) flow backwards to left atrium

12. Left ventricle
--> pumps oxygenated blood
--> to body tissue (via aorta).

13. Semilunar/aortic valves
--> prevent blood (from aorta) flowing backwards (into left ventricle).

14. Aorta
      --> carries oxygenated blood
      --> from left ventricle
      --> to the rest of the body.

15. Septum separates the right and left side of the heart.

Simplified version of heart

Gaseous Exchange in Mammals

2011-05-14T03:00:00.012+08:00

(A) Gaseous exchange in mammals

Respiratory tract consists of: nostril, nasal cavity, pharynx, trachea, bronchi + bronchioles.

Gaseous exchange occurs at the alveoli.
Alveolar wall = single layer of squamous epithelium cells.
Capillary wall = flattened endothelial cells.
Thin layer of alveolar wall + rich network of blood capillaries à enhance gaseous exchange between alveolar sac + blood.

Deoxygenated blood - enters the lungs - thrugh pulmonary arteries.
Oxygenated blood - leaves the lungs - through pulmonary vein.
The rate of O₂ + CO₂ diffusion in the alveolar à depends on partial pressure of the gases in the alveolar air.

9. In the lung:

à PO₂ in the alveolar air is higher than blood

à O₂ diffuse rapidly from alveolus

à to blood plasma.

In the peripheral tissues:

à PO₂ is lower than blood

à O₂diffuses out from blood

à to tissues.

O₂ + CO₂ à low solubility in blood plasma
CO₂à mainly transported as hydrogen carbonate ion (HCO₃⁺).
In the tissues

à PCO₂ is higher than blood

à CO₂ diffuses out

à into the capillaries.

(B) Gaseous exchange in mammals

Blood carries CO₂ in 3 forms:

· dissolved gas (8%)

· HCO₃^- ion in the plasma (73%)

· carbamino haemoglobin in the red blood cells (19%)

A large amount of CO₂

· combines with H₂O in the red blood cells (RBC)

· to form carbonic acid (H₂CO₃)

· then ionizes to form H⁺ + HCO₃^-

HCO₃^- from the red blood cell:

· diffuse out into the plasma.

· loss of negatively charge HCO₃^- from the red blood cell

· balanced by the inward diffusion of -ve chloride ions (Cl^-) = chloride shift.

In the lungs.

à PCO₂ is lower than in the blood.

à CO₂diffuses out

à into alveoli.

In the plasma:

1. dissolved CO₂ diffuses out into the alveolar air.

2. Carbamino haemoglobin:

à dissociates

à form CO₂+ haemoglobin.

3. Hydrogen carbonate ions (HCO₃^-):

à diffuse into the red blood cells

à reacts with H⁺

à form carbonic acid (H₂CO₃).

à dissociates

à form H₂O + CO₂

à CO₂ diffuses out into the alveolar air

à exhaled.

(C) Gaseous exchange in mammals

1. O₂ = transported by the haemoglobin molecule in the red blood cells.

2. Each haemoglobin molecule à carries 4 mol of O_2.

3. Each polypeptide chain contains:

· 2 subunits of alpha polypeptides chains

· 2 subunits of beta polypeptides chains.

4. Haem:

à prosthetic group of haemoglobin.

à as a porphyrin ring with a ferum ion (Fe2+) in the middle.

à each capable of carrying a single O₂ molecule attached to the ferum ion

à porphyrin ring shows strong cooperative O₂ binding to the haemoglobin.

5. When one mol of O₂binds to one of the haem group in the haemoglobin

à produces a conformational change in that subunit

à transmitted to the other 3 subunits

à facilitate O₂binding to the rest of the polypeptide.

à concerted conformational change of the subunits

à increases affinity of haemoglobin for O₂

à resulting in sigmoid shape for the O₂dissociation curve of the haemoglobin.

6. The cooperative effect is reversible

à when one subunit of oxyhaemoglobin unloads its O₂,

à other three quickly follow suit

à conformational change

à lowers its affinity for O₂.

7. Relationship between PO₂ and % saturation of haemoglobin with O₂
à represented by O₂dissociation curve = sigmoid.

8. The O₂dissociation curve shows:

à when haemoglobin is exposed to a gradual increase of PO₂,

à it absorbs O₂rapidly at first

à but more slowly as the PO₂ continues to rise.

9. The % of O₂saturation of haemoglobin = 95%

à when blood flows through the lungs (PO₂ = 105 mmHg).

10. The % of O₂saturation of haemoglobin = 70%

à when blood flows through a moderately active/resting muscle (PO₂=40 mmHg).

11. As the blood from the lungs reaches the muscle at rest:

à 25% of the O₂carried in the heamoglobin is unloaded to the surrounding tissues

à for cellular respiration.

à 70% of the oxygen is still retained by the haemoglobin.

12. The % of O₂saturation of haemoglobin is 40%

à when the blood flows through the active muscle at PO₂ of 20 mmHg.

13. When the muscle is active:

à haemoglobin readily unloads 55% of the oxygen

à still retains 40%.

14. During exercise:

à active tissue is in demand for O₂to produce energy.

à slight drops in PO₂ (between muscle at rest + muscle during exercise.)

à enough to cause a relatively large increase in the amount of O₂the blood unloads.

15. The increase of CO₂ conc/decrease in blood pH:

à will induce haemoglobin to unload more O₂.

à affinity of haemoglobin to O₂is lower.

à O₂dissociation curve shifts to the right = Bohr effect.

16. Foetal haemoglobin:

à has a higher affinity for O₂than the maternal haemoglobin

à therefore, O₂dissociation curve lies to the left.

17. O₂must easily dissociate from the maternal haemoglobin to the foetal haemoglobin

à therefore, easily transferred from maternal to foetal blood.

18. Myoglobin:

à higher affinity for O₂than haemoglobin.

à Therefore, dissociation curve lies to the left.

Haemoglobin:

à has a lower affinity for O₂ than myoglobin.

19. In the muscle:

à O₂dissociates from haemoglobin

à transferred to myoglobin to be stored.

Lung volume

2011-05-02T21:34:00.003+08:00

1. Spirometer used to measure lung capacity.

2. Breathing movement is traced in a form of graph = kymograph.

3. Total capacity in human lungs = + 5 dm3 of air.

4. Tidal volume - air exchanged in normal breath = + 0.5 dm3 .

5. Healthy person breaths + 15 to 20 times per minute.

6 Vital capacity - max volume of air exchanged during forced breathing = raised to 3.5 dm3.
7. Vital capacity - has two components:

=> inspiratory capacity

=> expiratory capacity

8. Residual volume - volume of air that remains in the lungs = + 1.5 dm3.

9. Total lungs capacity = 5.0 dm3.

Breathing process

2011-04-26T02:32:00.015+08:00

1. Breathing control centre are:

located in two major regions (medulla oblongata + pons).
in medulla - sets the basic rhythm,
in pons - moderates it smoothing out the transition between inhalation + exhalation.
send impulses to the diaphragm + external intercostals muscle.

2. The central chemoreceptors (lies near the breathing control centers):

detet the changes in pH of the cerebospinal fluid (CSF).
stimulate the breathing centre
slow down or speed the rhythmic discharge of nerve impulses

3. Carotid bodies are

found in the carotid artery in the neck.
chemoreceptor with nerve endings in the wall of carotid artery
monitors the changes of blood pH in the carotid artery.

4. Aortic bodies are

found in aorta.
chemoreceptors that monitor the changes of blood pH.
nerve endings in the wall of aorta.

5. Aortic and carotid bodies:

also called peripheral chemoreceptors.
impulses are relayed to the breathing control centres.
change of CO2 conc. in the blood triggers a series of chain reactions.
blood CO2 conc. back to normal,
negative feedback loop.

6. In the blood plasma:

CO2 released by cellular respiration
reacts with H2O to form carbonic acid (H2CO2)
dissociates to form hydrogen carbonate ions (HCO3+) and hydrogen ions (H+).
increase in hydrogen ions (H+) conc.
increase the acidity of the blood plasma,
decreasing the pH.

7. In the region of medulla

CO2 diffuses into CSF from the surrounding capillary.
then reacts with H2O in the fluid to form carbonic acid (H2CO3).
dissociates to form hydrogen carbonate (HCO3+) and hydrogen ions (H+).
The acidity in the CSF increases
resulting in the decreases in the pH.

8. When blood flows through Peripheral Chemoreceptors (from aortic + carotid bodies) + Central Chemoreceptor

à detect increase in H⁺ conc

à send impulses to breathing control centre (in medulla oblongata)

à sends impulses to diaphragm + external intercostals muscles to contract faster

à breathing rate increases (to expel excess CO2)

à lungs expand (for faster breathing)

à stimulates stretch receptors (in lungs)

à send impulses to the breathing control centre

à sends impulses (via parasympathetic nerve) to the diaphragm + external intercostals muscle

à to slow down the contraction

à breathing rate returns to normal

à negative feedback reaction.

Anaerobic Respiration (Fermentation)

2011-04-19T22:29:00.004+08:00

1. Anaerobic respiration (fermentation):

- respiration takes place in the absence of O2
- occurs only in the cytoplasm.

- produces: pyruvate, 2 NADH + 2 mol ATP
- pyruvate + NADH accumulate in cytoplasm

2. - pyruvate + NADH accumulate in cytoplasm
--> causes tissues to run out of H acceptor (NAD+) - limited supply.

--> glycolysis may not occur.

--> need for an alternative H acceptor.

--> pyruvate or acetaldehyde becomes the H acceptor.

--> pyruvate can undergo both aerobic and anaerobic respiration.

3. In plants:

- pyruvate undergoes alcohol fermentation --> produce ethanol,
- occurs in roots of the plants (water logged conditions).

4. In animals:

- pyruvate undergoes lactic acid fermentation --> produce lactic acid
- occurs in the muscles during vigorous activity + strenuous exercise.

7. Fermentation products are used commercially.

- Wine, methanol and formic acid are formed by alcohol fermentation.

- Yogurt, cheese and soy sauce are formed by lactic acid fermentation.

Aerobic Respiration - Electron Transport System

2011-04-16T03:14:00.006+08:00

1. Electron transport system = chain of e- acceptors (embedded in the inner membrane of the mitochondrion).

2. e- transferred from NADH + FADH2 via several e- acceptors --> final e- acceptor (molecular O2).

3. energy produced = ATP (thru oxidative phophorylation).

4. inhibitors = cyanide + CO - inhibit the function of ETC.
5. Cyanide + CO --> block activity of cytochrome oxidase --> inhibit the ETS --> no production of H2O --> no activation of ATP synthase --> no ATP production.

6. ETS:

accepts e- from energy carriers (NADH + FADH2) from glycolysis + Krebs cycle.
consists of mostly cytochromes (proteins with prosthetic groups).
produces H2O from O2 at the end
1 NADH produces 3 ATP
1 FADH2 produces 2 ATP.
net energy gain = 34 ATP molecules.

Aerobic Respiration - Krebs cycle

2011-04-16T02:16:00.003+08:00

1. Krebs cycle:

biochemical reactions occurring in all living cells,
in the inner membrane of mitochondria.
involves a metabolic pathway (pyruvate --> CO2 + H2O) to generate energy.
also called citric acid cycle or trycarboxilic acid (TCA) cycle.

2. Acetyl CoA initiates the Krebs cycle (by combining with oxaloacetate (4C) --> citrate).

3. Citrate is decarboxilated and dehydrogenated.

4. Energy stored = NADH, FADH2 and GTP.

5. 2 mol of CO2 are released (as waste product).

6. NAD + FAD = H acceptors.

7. 1 mol of ATP is gained.

8. provides H for use in ETC (as energy for formation of ATP).

Aerobic Respiration - Glycolysis

2011-04-15T02:56:00.003+08:00

Aerobic respiration is a process:

which sugars are broken down - to release energy - in the presence of O2.
occurs in three stages: glycolysis, Krebs cycle, electron transport system.

Glycolysis:

takes place in cytoplasm of a living cell,
glucose --> 2 mol of pyruvate.
series of reactions catalysed by specific enzymes
involves two phases: energy investment phase and energy pay off phase.

5. Energy investment phase:

glucose is broken down into 2 mol of PGAL
2 mol of ATP are utilized in this phase.

6. Energy pay off phase:

2 mol of PGAL --> 2 mol of pyruvate.
4 ATP is formed by substrate level phosphorylation.
The net = 2 ATP + 2 NADH.

Experiment 14: Structure of flowers

2011-04-15T02:20:00.000+08:00

Investigating...the flowers...and friends.

Must... must finish....must finish today!

Delonix regia in half.......

Hey!...Where's the ovary???

Concentrate....concentrate.........ohm..

draw....draw.....draw....z z z z!

The orchid is cut into equal halves.

Alternative mechanism of C fixation occurs in C4 and CAM plants

2011-04-14T09:32:00.004+08:00

C4 plants:

1. occurs both in mesophyll + bundle sheath cells.

2. CO₂ fixation is catalyzed by PEP carboxilase in mesophyll cells and sugar formation by RUBISCO in bundle sheath cells via Calvin cycle.

3. First product of CO₂ fixation is a 4C compound oxaloacetate in C4 plants.

CAM plant:

1. live in hot climatic conditions

2. both C₃ and C₄ cycles occur.

4. fix CO₂ during the night + synthesise sugar during the day.

5. G3P produced = used for the synthesis of sugars, amino acids and fatty acids.

6. Sugars formed = glucose, sucrose, starch + cellulose.

7. Lipids:

· formed from glycerol + fatty acids.

· Glycerol = formed directly from G3P

· fatty acids = built from acetyl coenzyme A.

8. Protein formed by: conversion of G3P --> acetyl Co A (enters Krebs cycle) --> α-glutarate --> glutamate --> transamination --> form amino acids + proteins.

Dark Reaction (Light Independent Reaction)

2011-01-13T01:28:00.007+08:00

1. Dark reaction (Calvin cycle):

Þ 2^nd stage of photosynthesis

Þ CO₂ - converted into sugar.

Þ takes place in the stroma (of chloroplast + bundle sheath cells).

Þ not dependent on light.

Þ cyclic process of enzyme catalyzed reactions.

2. It involves three steps:

Þ CO₂ fixation

Þ reduction

Þ regeneration.

3. During CO₂ fixation:

Þ CO₂ combines with RuBP(5C) to form G3P (catalysed by Rubisco - also involved in the photorespiration process).

Þ first product = glyceraldehyde 3 phosphate (G3P)

4. ATP and NADPH are utilised (from light reaction).

5. 5 molecules of G3P are utilised for regeneration of RuBP.
4. C₃, C₄ and CAM plants (have different anatomy + physiology)

5. C₃ plants:

Þ mesophyll cells have chlorophyll.

Þ open their stomata during the night.

Þ live in moderate climate.

6. C₄ plants:

Þ have mesophyll cells + bundle sheath cells.

Þ have Krantz anatomy.

Þ live in dry climatic conditions.

Þ adapt themselves to prevent water loss by closing stomata during day time.

Photosynthesis

2010-11-30T19:48:00.005+08:00

Chloroplast = organelle cotaining photosystem (where photosynthesis occurs).
A photosystem consists of:

chlorophyll molecules (primary pigment)
accessory pigments (chrolophyll b and carotenoids)
proteins
associated electron acceptors.

PS I (photosystem I) absorbs light of wavelength 700nm
PS II (photosystem II) adsorbs light of wavelength 680nm
Paper chromatography technique = to separate different pigments of a leaf.
Each pigment is identified by the characteristic coloured peak formed on the chromatography paper.
The amount of absorption of the pigments and the rate of photosynthesis at different wavelength of light can be graphically represented.
Absorption spectrum = indicates the amount of absorption at different wavelengths of light.
Action spectrum = indicates the rate of photosynthesis at different wavelengths of light.
Chlorophyll a and chlorophyll b absorb blue and red light
Carotenoids absorb only blue light.
The absorption spectrum and action spectrum graphs show peaks and valleys.
Engelmann conducted a series of experiments using filamentous algae. He used the motile, oxygen sensitive bacteria call Pseudomonas sp.
Chloroplasts were illuminated with different wavelengths of light and the movement of the bacteria was observed.
Bacteria were found to group around the region of the chloroplasts illuminated by red and blue wavelengths of light.
Engelmann concluded from the experiments that photosynthesis can occur only when the chloroplasts are illuminated by red and blue light

Light Reaction in Photosynthesis

2010-11-26T15:27:00.018+08:00

Happens = in photosystem (in thylakoid membrane).
Involved only PSI (In cyclic photophosphorylation)
Energised e-:

are released from the excited chlorophyll a (P700)
is picked up by a primary acceptor.
pass through electron transport chain
return to P700
by releasing energy (to produce ATP from ADP and Pi).

Cyclic photophosphorylation
Involved both PSI and PSII (In non-cyclic photophosphorylation)
Energised e- :

are released from the excited chlorophyll a (P680)
is picked up by the primary acceptor.
are transported to cytochrome complex
through the elcetron carrier plastoquinone
during which its energy is trapped to form ATP.

Electron hole:

is formed in P680 due to the transport of the excited electron
is filled up by the electron produced during photolysis.

Low energy level e-:

from the cytochrome complex are transported to P700 through plastocyanin.
transportedfrom P700 to NADP for reduction (catalyzed by NADP+ reductase (enzyme)
via the primary acceptor and ferredoxin.

Net energy gain (during non-cyclic photophosphorylation) = 1 mol ATP + 1 mol NADPH.

Non-cyclic photophosphorylation

Photosynthesis

2010-11-13T00:07:00.006+08:00

Photosynthesis = process : carbohydrate is synthesised by using sunlight, CO2 and H2O.
Photosynthesis occurs in the thylakoid membrane of the chloroplast (contains many pigments : chlorophyll a, chlorophyll b and carotenoids.
These pigments are grouped together = photosystems.
Two types of photosystems : photosystem I and photosystem II.
Both photosystems absorb light energy--> convert it into biochemical energy.

Quadrat making by L6ScG and L6ScZ

2010-11-11T20:06:00.013+08:00

Mural painting by Lower 6 students.

2010-11-10T00:36:00.007+08:00

Aiya!...very... very hot la............!

Faster laaa... L6ScZeta...very hot laaa..!

Biology STPM 2010

2010-11-05T01:56:00.003+08:00

Paper   : Biology 2 (structure and essay)
Code    : 964/2
Date     : 30 Nov 2010 (Tuesday)
Time     : 2.00 pm - 4.30 pm
Duration: 2 hours 30 mins

Paper   : Biology 1 (multiple-choice)
Code    : 964/1
Date     : 2 Dec 2010 (Thursday)
Time     : 2.00 pm - 3.45 pm
Duration: 1 hours 45 mins

Biodiversity: Threat of extinction

2010-11-05T01:24:00.002+08:00

Factors that threaten the extinction of biodiversity:

1. deforestation

2. logging

3. shifting cultivation

4. excessive use of agrochemicals

5. illegal hunting and wildlife trade

6. destructive fishing practices

7. pollution.

Biodiversity in Malaysia

2010-11-05T00:36:00.009+08:00

Biological diversity (biodiversity) :
total number of species within an ecosystem and to the resulting complexity of interactions among them. (It includes all the range of ecosystems and varieties of plants, animals and micro organisms within them).

Biodiversity can be divided into:
- ecological diversity

- species diversity

- genetic diversity.

Ecological diversity: collection of different environment types in a region. (In Malaysia, ecological diversity includes coastal vegetation, tropical rain forest up to the montane vegetation).

Species diversity: variety of living things on earth. It includes mammal, reptiles, amphibians, birds, insects and invertebrates.

Genetic diversity: variations at the level of individual genes. (These variations are caused by meiosis during sexual reproduction, artificial selection and genetic recombination).

Genetic diversity provides a mechanism for populations to adapt to their ever-changing environment. The more variations, the better the chance that at least some of the individuals will have an allele that is suited for the new environment.

In Malaysia: genetic diversity can be seen in both wild and domesticated animals, plants and insects.

Potato strips experiment by L6ScZeta

2010-09-30T22:29:00.004+08:00

Potato strips experiment by L6ScGamma

2010-09-30T22:24:00.002+08:00

2010-09-27T22:54:00.002+08:00

Kingdom Protoctista:

1. Subklngdom Algae

(i) Phylum Chlorophyta (green algae)

(ii) Phylum Phaeophyta (Brown algae)

2. Subkingdom Protozoa

(i) Phylum Rhizopoda (Rhizopods)

(ii) Phylum Ciliophora (Ciliates)
(iii) Phylum Zoomastigina (Flagellates)

2010-09-23T10:08:00.001+08:00

Comparing Prokaryote and Eukaryote

Classification of organisms

2010-09-20T00:56:00.002+08:00

Living organisms can be classified into five-kingdom system:

1. Prokaryotae

2. Protoctista

3. Fungi

4. Plantae

5. Animalia.

Classification of viruses

2010-09-20T00:50:00.002+08:00

Classification of viruses would be based on:
(a)          type of nucleic acid
(b)         shape of protein coat
(c)          type of host cell they invade (plant viruses, animal viruses or bacteriophaees, viruses which attack bacterial).

2010-09-18T14:43:00.001+08:00

Blog building course was held on 16/9/2010 until 19/9/2010 at Hotel Seri Pelang, Muar.

Insect and arthropods

2010-09-18T10:52:00.003+08:00

What is biodiversity?

2010-09-18T02:02:00.001+08:00

Biodiversity (biological diversity) is usually considered at three different levels:

(a) Genetic diversity

(b) Species diversity

(c) Ecosystem diversity