What is Cardiac cycle

Cardiac cycle is the sequence of event in one heartbeat which consist of one systole and diastole

sequence of event is atrial systole, ventricular systole , ventricular diastole and atrial diastole

During atrial systole, excitatory of electrical impulses which generated in the sinoatrial node (SA node) spread to the both the right and left atria

This causes the atria to contract

The  contraction causes the pressure to increase in both the atria

AV valve open

This will allow the blood to flow from the atria to the ventricles

During ventricles systole , excitatory impulse move to atrioventricular node (AV node) down the Bundle of His and Purkinje fibre to the ventricular muscles

The ventricular muscle contracts (ventricular systole)

The blood pressure inside the ventricles increased

AV valve closed wben ventricular pressure is higher than atrial pressure

 The closing of AV valve produced the first heart sound 'lub'

The ventricular pressure rises and exceeds in the aorta and pulmonary artery

This cause the semilunar valves open

This allows the blood to flow from left ventricle to aorta and from right ventricles to pulmonary artery

During ventricular diastole , ventricles relax

Pressure in ventricle is lower than the pressure inaorta and pulmonary artery

Blood in the arteries start to flow backwards into the cups of semilunar valves

this will close the semilunar valves and produced the second heart sound 'dub'

As the ventricles xontinues to relax , the ventricular pressure falls rapidly 

When ventricular pressure less than atrial pressure , the AV valve are forced to open

During atrial diastole, atrial will relax and the right atria receives deoxygenated blood from the body tissues to vena cava

Left atria received oxygenated blood from the lung to pulmomary vein

Mechanism of transmission

Spread of impulse across synapse

Calcium gated channel in the presynaptic membrane opens when the nerve impulse arrives the synaptic knob

Calcium ion diffuse quickly from the (synaptic cleft/ extracellular fluid) into the synaptic knob

The influx of calcium ion causes the synaptic vesicles to fuse with presynaptic membrane

The vesicles release neurotransmitter into the synaptic vesicle to fuse with presynaptic membrane

The vesicle release neurotransmitter

into the synaptic cleft by exocytosis

Neurotransmitter diffuse across the synaptic cleft & bind to the receptor on postsynaptic membrane

This triggers the sodium channel to open

Sodium ion diffuse into postsynaptic membrane , depolarising the postsynaptic membrane

A new potential is known as excitatory postsynaltic potential (EPSP)which is genrated if the EPSP is large enough to reach the threshold level

An action potential is generated

The action pptential is transmitted along the postsynaptic neurone

Spread of impulse across synapse (will be updated soon)

Steroid hormone and Non Steroid hormone

Steroid hormone 

Steroid hormone such as aldosterone is secreted by the adrenal cortex

These hormones are lipid soluble molecules that are able to diffuse through plasma membrane of target cells

the hormone combines with a receptor either in the cytoplasm or in the nucleus

ths steroid receptor complex moves theough the nuclear pores and into the nucleus

Steroid receptor complex binds to specific region of DNA stimulatinv the transcription of a gene in DNA

the messenger RNA (mRNA) moves through the nuclear pore into the cytoplasm

The mRNA binds to the ribosomes

Then it is translated into protein or enzyme for certain physiological process

Non steroid homone

Non steroid hormone such as axrenaline act as 1st messenger

the hormone binds to specific receptor proteins in the cell surface membrane

the hormone receptor complex binds with G-protein

Once G-protein is activated , it moves to stimulate the enzyme adenyl cyclase

The activated adenyl cyclase converts ATP into cAMP(cyclic adenosine monophosphate)

cAMP acts as a second messenger and activate protein kinase

The activated protein kinase activates the enzyme phosphorylase which catalyses fhe hydrolysis of glgcogen in glucose

Glucose is oxidised to release energy

At each stage in the process , an amplification process occurs.

Only few of adenyl cyclase are needed to activate many molecule of protein kinase and so on

This is known as cascade effect

Role of Antidiuretic and Aldosterone hormone

Control of water content of blood

DURING HIGH OSMOTIC PRESSURE

low water intake , high salt intake , sweating excessively

Osmoreceptor in hypothalamus is stimulated

• This will send impulse to posterior pituitary gland
  
• This will also send impulse to thirst centre cause feeling thirsty(induce more water to intake)

Wall of distal convoluted tubule and collecting duct increases its permeability to water

More water is reabsorbed 

More concentrated urine with reduced volume is excreted (hypertonic urine)

Then the blood osmotic pressure return to normal

Control of blood sodium and potassium ions of urine

DURING HIGH BLOOD SODIUM LEVEL

due to high salt intake

Produce a high pressure and blood volume

• Juxtaglomerular complex is not stimulated.No rennin and angiotensin II is formed
• Heart atrial cardiac muscle secrete atrial natriuretic peptide hormone. Natriuretic peptide hormone inhibit the secretion of aldosterone by adrenal gland

Less aldosterone is released from adrenal gland so that to decrease the permeability of distal convoluted tubule and collecting duct to sodium ion by decreasing the nunber of sodium potassium pump

Less sodium ion is reabsprebed in distal cpnvoluted tubule and collecting duct

The blood sodium level return to normal level

Regulation of breathing mechanism

The breathing control centres are stimulated in the medula oblongata

The breathing controls send more nerve impulses via phrenic nerve and thoracic nerve to the thoracic cavity and receive nerve impulse from the chemoreceptors in carotid bodies and aortic bodies

During vigorous exercise , the partial pressure of carbon dioxide (CO2) in the blood increases and the blood pH drops

This is detected by chemoreceptors in the carotid artery and impulses are sent to stimulate the inspiratory and the cardiovascular centre in the brain

The inspiratory nerve to stimulate the contraction of the external intercostal muscles of the rib cage

The phrenic nerve to stimulate the contraction of radial muscles of the diaphragm

Both contractions bring the rib cage outward and upward to increase the volume of the lungs and decrease its pressure

Atmospheric air is forced or inhaled into the lungs

As the bronchial tree of the lungs is stretched, it stimulates the stretch receptors which then send impulses to the expiratory centre through the vagus nerve

The expiratory centre inhibit inspiration amd stimulate expiration

During expiration, the rib cage and the diaphragm fall back to their original positions (due to natural recoiling) decreasing the lung volume but increasing its pressure

Air is forced or exhaled out of the lungs

During forced exhalation, the internal intercoastal muscles will contract to bring the rib cage downwards and inwards

The expiratory centre then become inactive and inspiration begins again

Inspiration and expiration are carried out more frequently to increase the rate of alveolar ventilation for faster gaseous exchange in the body

At the same time, cardiovascular centre sends impulse throughthe sympathetic nerve to the heart to increase the cardiac frequency

High levels of CO2 also causes the blood pressure to increase

This will cause the walls of carotid arteries to stretch and stretch receptors are stimulated

Impulses are sent to the cardiovascular centre through the afferent nerves

The cardiovascular centre will then respond by stimulating the heart to reduce its cardiac frequency and the blood vessels tp.dilate thus lowering the blood pressure.

Mechanism of Enzyme

Induced fit mechanism

The active site is not complementary to the substrate
But the active site of enzyme is flexible and can change the active site during reaction
When collision occurs btw enzyme and substrate, substrate can bind to the active site of enzyme
The binding site of substate induces the enzyme to change its shape
To enable substrate to fit precisely to the active site
An enzyme substrate complex is formed
Enzyme stretched the existing bond to facilitate the reaction btw enzyme and substrate
Product is formed and released from active site
Enzyme changes back to its position


diagram from https://slideplayer.com/slide/5991600/

Lock and key mechanism

Active site of the enzyme represents the lock while substrate as the key
An enzyme is a large globular protein with specific 3D shape
The active site which is made up of specific arrangement of amino acids
The active site of the enzyme is the site for substrate to bind
The active site has a specific conformation that is complementary to the shape of substrate
Binding site of the enzyme forms an enzyme substrate complex
Activation energy and product are formed and released
At the end of the reaction the active site of the enzyme remain unchanged and the enzyme can be reused


diagram from https://www.123rf.com/photo_36876740_the-lock-and-key-mechanism-labeled-diagram.html



diagram from http://ibbiology.wikifoundry.com/page/Describe+the+induced-fit+model

Mesohlson Experiment

There are three types of hypothesis to explain how DNA replication take place.

Three hypothesis are conservative replication, semiconservative replication, dispersive replication.

Mesohlsohn Stahl used escherichia coli (E.coli) with heavy nitrogen isotope 15N.

This is to label all DNA with heavy nitrogen isotope 15N.

Bacteria with 15N transferred into medium containing normal isotope 14N .

Sample were removed at fix interval corresponding to the generation time of E.coli at a specific temperature.

DNA from different generations were extracted N-centrifuged in a solution containing CsCl to separate denser DNA containing 15N from lower DNA containing 14N.

Position of DNA with 15N and DNA with 14N was measured with uv light.

In generation zero, all DNA containing 15N on both strand of double helix forming a dark band near the base of centrifuge.

In generation one, all DNA 15N on one strand and 14N in another strand, forming a band btw heavy & light band.

in generation two, half of DNA were hybrid.another half were light DNA with 14N.

in generation 3, DNA with 14N three times thicker than 15N and number of hybrid DNA remain the same.

For the result of 1st generation ,it eliminates the conservative hypothesis not explain presence of hybrid DNA.

For the result of second generation, it eliminates dispersive hypothesis because the hypothesis not explaining the presence of light DNA in second generation.

Therefore Mesohlsohn & Stahl experiment proved that DNA replicate semiconservatively.


diagram from http://www.notesonzoology.com/dna-replication/dna-replication-modes-ingredients-and-ingredients/2406



diagram from  http://www.keywordhouse.com/bWVzZWxzb24gYW5kIHN0YWhsICBzZW1pY29uc2VydmF0aXZl/

diagram from  http://www.keywordhouse.com/bWVzZWxzb24gYW5kIHN0YWhsICBzZW1pY29uc2VydmF0aXZl
/


diagram from
http://www.keywordhouse.com/bWVzZWxzb24gYW5kIHN0YWhsICBzZW1pY29uc2VydmF0aXZl

Beadle & Tatom's experiment

Neurospora can grow in minimal medium if it is not mutated

they can synthesise the enzyme which is needed to produce amino acids

Beadle and Tatum had grow Neurospora in minimal culture

Then, they exposed the Neurospora with X-ray caused mutation in Neurospora

They found that mutated Neurospora unable to grow in minimal medium because gene that codes for the synthesis of enzyme used to produce certain amino acid is mutated

The mutated neurospora only grew in complete culture which contain all 20 amino acid

Thus  they isolate the mutated neurospora and grew them in minimal medium with a type of amino acid

Altogether there are 20 minimal medium with 20 different amino acid each

They found that neuropspora can only grew in presence of particular amino acid which is arginine

They had made one gene one enzyme hypothesis means the gene that code for the synthesis of enzyme that required to make arginine is mutated

One gene one enzyme hypothesis is then modified to one gene one protein hypothesis as the gene coiled code for other protein not necessary arginine

When it is found out that a protein can consist of more than one polypeptide chain

The hypothesis is further refined to one gene one polypeptide hypothesis

diagram from Beadle & Tatum experiments (mun.ca)

diagram a

diagram b

diagram a & b from
Using Microbiology to Discover the Secrets of Life | Microbiology (lumenlearning.com)

Sulphur cycle

Volcanoic eruption or industrial activities spill out sulphur dioxide gas (SO2 ) into atmosphere.

Rain brings it down forming acid rain.

Sulphate (SO₄^2-) dissolve in soil and absorbed by plants for synthesis of protein.

Sulphate is reduced to organic R-SH group which used by plants to synthesis amino acid systeine , protein & coenzyme A.

The sulphur containing organic compounds are passed to herbivores when they eat plants.

The sulphur is transferred to carnivores along the foood chain.

When the animal and plants die , decomposed aerobically back to form sulphate.

Sulphur containing organic compounds in the organism may be anaerobically converted to hydogen sulphide (H₂S )

Sulphate in soil will change into H₂S by Desulphovibrio (sulphate reducing bacteria)

H₂S are converted in the hotspring into sulphur by bacteria Chromatin or Chlorobium.

Sulphur then oxidised by bacteria to form Sulphate back to the soil.

diagram from Bio 105 Chapter 3 (slideshare.net)

Phosphorus cycle

The major reservoir of phosphorus is rock.

In the rock phosphorus is bound to oxygen to form phosphate.

As water flows over rocks containing phosphorus(river water flows through) it erodes the surface and carries inorganic phosphate into the soil to be taken up by plants.

In plant cells, the phosphate is incorporated into biological molecules like phospholipids , protein and nucleic acid.

When animal feeds on the plant, phosphorus is transferred.

Phosphorus move along the food web as organism consume it and excretion of phosphorus also occur.

Decomposers will decompose waste and dead organisms ; release inorganic phosphate into the soil and water bodies.

Phosphorus released is used by terresterial and aquatic producers.

Phosphorus enter aquatic system as dissolved phosphate which is absorbed by algae and aquatic plants.

The algae and aquatic plants are then consumed by zooplanktons and inturn by fishes.

Some phosphate in the aquatic system returns to lamd via fish and invertebrates eaten by birds.

The faeces of bird contain phosphate which will absorbed by land plants.

Some phosphate can be carried by rivers into the ocean and remain in the seabed for millions of years.

In time, geological uplifting may expose these sediments and reenter the phosphorus cycle.

Phosphorus also enter the water ecosystem artificially through fertilisers.

Leaching of phosphate from agriculture areas increases the phosphate in aquatic habitats and stimulates algal growth.

The completion of phosphorus cycle is very slow because abiotic storage of phosphorus is in the form of rock.

diagram from: Phosphorus Cycle | Science | ShowMe

Selection

Selection  

1. a process whereby one or more factors acting on phenotypes favour the transmission of particular alleles to the following generation
   
2. process whereby organisms which are better adapted to their environment survive and reproduce, while those less adapted fail and usually die
3. two types of selection ~ natural selection ~artificial selection

Natural selection

process by which individual organism with favourable traits are more likely to survive and reproduce than those unfavourable traits

process brings about evolution and adaptation(enable population to change and adapt to different chromosomes)

results in more favoured traits and less unfavoured traits

• individuals with beneficial traits are more likely to be selected that is to have more offspring
  
• those traits have a heritable component, tend to become more common in next generation
• alleles with an average result in greater fitness will become more abundant in the next generation

Natural selection does not acts directly on genotype but acts on phenotype

result in evolutionary change

there are many types of natural selection found in population

• stabilising
• disruptive
• directional
• sexual
• polymorphism

Artificial selection

1. process of intensional or unintensional modification of a species through human action which encourages the breeding of certain traits over others. (Breeder selects the desired characteristics)
2. genotype is altered to produce a new strain of the organism for specific purpose.

Human preferences or influences have a significant effect of the evolution of particular population or species

include outbreeding and inbreeding

eg. domestication of corn & domesticated chicken

*click the link for more info(will be updated soon)

chemistry note chap 11

CHAPTER 11 GROUP 14 11.1 physical properties of group 14 Electrical conductivity carbon (C)               non metal silicon  (Si)              metalloid germanium  (Ge)     metalloid tin  (Sn)                   metal lead  (Pb)                 metal Increase in number of occupied electron shell increase in electrical conductivity increase in screening effect > nuclear charge Zeff decrease (force of attraction between nucleus and valence electron weaker) Atomic radius increase Valence electron more delocalised Metallic character increase Melting point decreasing down the group C  Si  Ge  Sn  Pb highest to lowest Carbon, Silicon, Germanium giant structure strong covalent bond btw atom required lots of energy to break covalent bond high melting point and boiling point Tin, Lead Both are metals due to large atomic size, metallic bond weaker Melting and boiling points weaker Lead bigger atomic radius than tin Lead higher melting point than tin Lead more close-packed structure than tin