1-2.2
Name the cell organelles.
Nucleus, cell SURFACE membrane, centrioles, ribosomes, rough and smooth endoplasmic reticulum, golgi apparatus, lysosomes, mitochondrion, chloroplasts, numerous tiny vacuoles/large central vacuole, cell wall
Biuret test
Biuret test:
The biuret test detects proteins by testing for the presence of peptide bonds
In the presence of dilute copper sulfate in alkaline solution, nitrogen atoms in the peptide chain form a purple complex with copper (II) ions.
To 2cm3 of the test sample, add an equal volume of 5% sodium hydroxide solution
Add 2 drops of 1% copper sulfate solution and mix
Observe any colour changes.
If there are proteins present in the test sample, the solution turns from light blue to violet.
If there are no proteins present in the test sample, the solution remains light blue.
Define viruses and its structure.
Viruses are obligate intracellular parasites that can reproduce only within a host cell. They cannot multiply outside a living host cell because they do not have any cellular components and other metabolic enzymes essential to carry out metabolism and synthesise proteins.
All virus consist of genetic material enclosed within a protein capsid
The capsid and enclosed genetic material is collectively termed as nucleocapsid
Only certain viruses carry enzymes within the capsid
Some viruses contain a membranous envelope
(Parts of the excretory system includes a pair of k_______, a pair of u_______, a u_____ b_____ and the u________. It also includes the h______ and the S_______ m______. Blood vessels include the r_______ a______ and the r_____ v_____.)
Parts of the excretory system includes a pair of kidneys, a pair of ureters, a urinary bladder and the urethra. It also includes the hilum and the Sphincter muscle. Blood vessels include the renal arteries and the renal veins.
Define an endocrine gland and homeostasis.
(Endocrine glands are ___________ which produce __________ and _________ them _________ into the ________. Homeostasis is the __________ of a _________.)
Endocrine glands are ductless glands which produce hormones and secrete them directly into the bloodstream. Homeostasis is the maintenance of a constant internal environment.
The cell is the basic unit of life
Organisms composed of a single cell is unicellular while organisms composed of many cells are multicellular
All cells arise from preexisting cells from division
The cell contains information which is used as instructions for growth, development and functioning
The cell is the functional unit of life in which chemical reactions that maintain life take place within it.
The 2 hypothesis for enzymes.
Lock and key hypothesis
The active site has a specific shape, to which the substrate binds.
The substrate is imagined to be like a key, whose shape is complementary to the shape of the enzyme active site
The shape of substrate or substrates is complementary and fits exactly into the shape of the active site to form the enzyme-substrate complex.
Once the reaction is completed with products formed, the products no longer fit into the active site and are released into the surrounding medium, leaving the active site free to receive new substrate molecules.
Induced fit hypothesis
The active site of the enzyme is a physically flexible structures.
Shape of substrate is still complementary to shape of the active site but does not fit exactly
Binding of the substrate to the active site induces a small conformational change in the shape of the enzyme.
This enables the substrate to fit more snugly into the active site when they form the enzyme-substrate complex.
The enzyme is able to perform its catalytic function more effectively.
Once the reaction is completed with products formed, the products no longer fit into the active site and are released into the surrounding medium, leaving the active site free to receive new substrate molecules.
Mode of action of antibiotics
Antibiotics
Antibiotics are drugs used to treat bacterial infections and are naturally made by microorganisms to kill or inhibit the growth of bacteria or fungi
They function by interfering with the growth and metabolic activities of the pathogen.
They are ineffective against viruses
They can inhibit the synthesis of bacterial cell walls. This causes the cells to expand, burst and die when excessive water enters the cell by osmosis, e.g. penicillin which prevent the synthesis of the peptidoglycan cell wall
They can inhibit the function of the bacterial cell surface membrane. Without the cell surface membrane, the bacterial cell is no longer protected from its environment, e.g. polymyxin which acts by breaking up the bacterial cell surface membrane.
They can inhibit ribosome function in protein synthesis. They prevent the bacteria from synthesising proteins and inhibit growth, e.g. tetracycline which binds to bacterial 70S ribosomes.
They can inhibit enzyme activity in the cytoplasm. Bacterial cells require a vitamin called folic acid for growth. Some antibiotics can inhibit the enzyme needed for the synthesis of folic acid, thereby inhibiting the growth of the bacterial cell.
They can inhibit DNA replication. Some antibiotics inhibit the enzymes needed for the replication of DNA in bacterial cells, preventing them from dividing via binary fission and stops reproduction.
Define metabolism, anabolism, catabolism and excretion.
(Metabolism is the _______ of all _______ occurring in the ________ of an organism. Metabolism = a______ + c_______. Anabolism are _________ where _____ molecules are built up into _______ molecules with a net _______ of _______. Catabolism are _________ where __________ molecules are broken down into ______ molecules with a net ______ of ______. Excretion is a process by which _______________ and ___________ are removed from the _________ of an ________.)
Metabolism is the sum total of all chemical reactions occurring in the cells of an organism. Metabolism = anabolism + catabolism. Anabolism are metabolic reactions where simple molecules are built up into complex molecules with a net intake of energy. Catabolism are metabolic reactions where complex molecules are broken down into simple molecules with a net release of energy. Excretion is a process by which metabolic waste products and toxic substances are removed from the body of an organism.
Structure of a neuron
(A vertebrate motor neuron consist of a cell body containing a _____ and a number of ______. _______ are like _____ which transmit ________ towards the cell body and _____ which transmit _____ away from the cell body. _____ which consists of _______ that wrap around the axon, and the ________ which is in between 2 ________.)
A vertebrate motor neuron consist of a cell body containing a nucleus and a number of nerve fibres. Nerve fibres are like dendrons which transmit impulses towards the cell body and axons which transmit impulses away the cell body. Myelin sheath which consists of Schwann cells that wrap around the axon, and the Node of Ranvier which is in between 2 Schwann cells.
Protein secretory pathway
Ribosome bound to the rough endoplasmic reticulum (rER) synthesise the polypeptide chain into the rER
The protein becomes enclosed in an ER/transport vesicle. The ER vesicle containing the protein buds off from ER,
travels and fuses with the cis face of the Golgi apparatus.
The GA chemically modifies, sorts and transports the proteins. The proteins move through the GA by Golgi vesicles budding off from one cisterna and then fusing with another cisterna.
The secretory vesicle containing the protein buds off from the trans-face of the GA, travels and fuses with the cell surface membrane. Thus, releasing the protein out of the cell.
For proteins that are needed for use within the cell, it is synthesised by free ribosomes.
Transport across cell surface membrane by facilitated diffusion.
In facilitated diffusion, transport proteins are involved. Transport proteins like channel proteins and carrier proteins are involved in the transport of hydrophilic molecules and ions across the hydrophobic bilayer.
It is a passive process like simple diffusion. The molecules or ions move down a concentration gradient, entering or leaving the cell with the help of transport proteins embedded in the phospholipid bilayer.
Most transport proteins are very specific (like enzymes).
Streptococcus pneumoniae
It is spread by respiratory droplets and droplet nuclei and from contaminated objects or surfaces
Transmissions occurs when a person inhales droplet nuclei containing Streptococcus pneumoniae, and the droplet nuclei traverse the mouth or nasal passages and reaches the alveoli of the lungs
Pneumococcal disease can also lead to life-threatening complications like pneumonia, which cause chest pain, cough breathing difficulties and fever
To diagnose pneumococcal disease, blood test, urine test, phlegm test, chest x-ray and spinal tap can test for the presence of Streptococcus pneumoniae.
To treat it, you must take antibiotics as prescribed to treat the disease
Get the pneumococcal vaccination as well
Avoid coming into close contact with people who have the disease
If you are sick, cover your mouth and nose with a tissue when you cough or sneeze. Wear a surgical mask.
Wash your hands with soap and water or rub with disinfectant if a surface contaminated by the bacterium is touched
Define ultrafiltration.
Ultrafiltration occurs in the glomerulus. It removes small molecules from the blood. Most of the blood plasma is forced out of the glomerular blood capillaries into the bowman’s capsule to form the glomerular filtrate. 2 conditions must be present for ultrafiltration to occur. Firstly, high hydrostatic pressure in the glomerulus. The difference in diameter between the afferent and efferent arteriole creates the high hydrostatic pressure in the glomerulus i.e. the afferent arteriole is wider than the efferent arteriole. It is the main force for ultrafiltration. Secondly, partially permeable membrane. The basement membrane that wraps the glomerular blood capillaries has very small pores to allow only water and very small molecules to pass through. Water, mineral salts, glucose, amino acids, nitrogenous waste products e.g. urea are filtered off during ultrafiltration. Blood cells, platelets and large molecules like proteins and fats are not filtered off.
Response to fall in blood glucose levels
(Blood glucose levels ______ below the ________ of around ____mg/____ml. The ______ in blood glucose level is detected by the ___________. This triggers the secretion of _________ by the alpha/beta cells in the _________ in the pancreas. _____ will be transported by the _______ to the liver and ____________ of stored _________ back to __________ in the liver. Simultaneously, _________ occurs, which is the conversion of __________ sources such as pyruvate, amino acids and glycerol to _________ in the liver. _______ is released into the ________, hence increasing blood glucose concentration until it returns to the ______________.)
Blood glucose levels falls below the reference point of around 90mg/100ml. The fall in blood glucose level is detected by the islets of Langerhans in the pancreas. This triggers the secretion of glucagon by the alpha cells in the islets of Langerhans in the pancreas. Glucagon will be transported by the blood to the liver and stimulates conversion of stored glucagon back to glucose in the liver. Simultaneously, gluconeogenesis occurs, which is the conversion of non-carbohydrate sources such as pyruvate, amino acids and glycerol to glucose in the liver. Glucose is released into the bloodstream, hence increasing blood glucose concentration until it returns to the reference point.
Functions of carbohydrates and lipids.
Carbohydrates:
It is a source of energy
Sucrose is a good transport sugar in phloem of plants. This is because it is very soluble and therefore can be moved in high concentrations and is chemically unreactive.
Polysaccharides such as starch and glycogen are good storage molecules. This is because they are large and insoluble → indiffusible through partially permeable membranes, they have compact shapes → allows more carbohydrates to be stored in cells and they are easily hydrolysed into monosaccharides.
Cellulose is a good structural polysaccharide. It is found in all plant cell walls as it has good tensile strength. It remains permeable to water and solutes.
Monosaccharides are required for synthesis of nucleic acids, disaccharides and polysaccharides.
Lipids:
Triglycerides serves as a form of storage of energy
Good thermal insulator to prevent excessive heat lost
To protect delicate organs
It is a component of cell membrane (especially phospholipids)
Structures of proteins (including P____, S______, T_____ and Q______ structure)
A protein molecule can be made up of either 1 polypeptide chain folded into a unique 3D shape, which is held by chemical bonds e.g. myoglobin or several polypeptide chains held together by chemical bonds into a unique 3D shape, e.g. haemoglobin
Each protein possesses its own characteristic 3D shape and structure known as its conformation.
There are 4 levels of protein structure: primary, secondary, tertiary and quaternary
The peptide bond is the only chemical bond involved in the primary structure
The secondary structure is the localised and repetitive folding of the pp chain and it is stabilised by hydrogen bonds between peptide linkages of the polypeptide backbone. (alpha-helix and beta pleated sheet)
The polypeptide chain folds and bends into the precise, globular 3D shape unique to the protein. The shape is held in place by the 4 types of interactions that occur between the R groups of amino acids at different regions of the pp chain: disulfide bond, hydrogen bond, ionic bond and hydrophobic interactions.
Quaternary structure is the combination of a number of polypeptide chains and may involve associated non-protein groups into a large. complex and functional protein molecule.
Mode of action of vaccines
Vaccination
A vaccine contains an agent that resembles a pathogen and prevents infectious diseases by stimulating lymphocytes to quickly produce antibodies when the pathogen invades.
Antigens are surface membrane proteins found on pathogens which leukocytes will recognise. When antigens bind to the specific receptors found on the leukocyte’s cell surface membrane, the white blood cell will respond either by secreting antibodies or killing the bacteria by phagocytes
Antibodies are proteins secreted by lymphocytes into the bloodstream that are bound only to specific antigens found on pathogens. They can kill the bacteria directly or mark the pathogens for destruction by macrophages and neutrophils.
A vaccine, containing an agent that resembles a pathogen (antigen) enters the body
The antigen binds to the receptor of a lymphocyte that is complementary to the shape of the antigen. This causes the lymphocyte to divide rapidly and differentiate into plasma B cells or memory B cells.
The plasma B cells produce and secrete large amounts of antibodies into the bloodstream.
The antibodies bind to the antigens present on the pathogen, either killing them or marking them for destruction by macrophages and neutrophils
Memory B cells remain in the body and can rapidly divide and differentiate into more plasma B cells during future infections by the same pathogen. This long-lasting protection is called immunity
Define selective reabsorption.
Useful substances are selectively reabsorbed from the filtrate formed by ultrafiltration
This occurs through the walls of the proximal convoluted tubule, Loop of Henle, distal convoluted tubule and collecting duct into the surrounding blood capillaries
The Proximal convoluted tubule reabsorbs all glucose, all amino acids and most mineral salts via active transport and diffusion, and reabsorbs most of the water via osmosis.
The loop of Henle reabsorbs some water via osmosis
The distal convoluted tubule reabsorbs some mineral salts via active transport and diffusion.
The collecting duct reabsorbs some water via osmosis. Excess water, excess mineral salts and nitrogenous waste products such as urea, uric acid and creatinine pass out of the collecting duct into the renal pelvis as a mixture called urine.
Response to a fall in temperature.
(_______ in the skin constrict and _________ dilate to allow ________ to flow through ________ under the skin surface. Thus, less heat is lost through the skin by r______, conv________ and cond_______. _______ becomes less active so there is a _______ production of sweat. Less ___________ is lost from the body. The _______ rate of the body ________ thus more heat is produced within the body. _________ also occurs, which is the ___________ of the muscles, which increases heat production. These actions increases blood temperature until it returns to the __________ point. The return to normal is detected by the _________. The removal of the __________ will stop the homeostatic action.)
Arterioles in the skin constrict and shunt vessels dilate to allow blood to flow through blood capillaries under the skin surface. Thus, less heat is lost through the skin by radiation, convection and conduction. Sweat glands becomes less active so there is a decreased production of sweat. Less latent heat of evaporation is lost from the body. The metabolic rate of the body increases thus more heat is produced within the body. Shivering also occurs, which is the spasmodic contraction of the muscles, which increases heat production. These actions increases blood temperature until it returns to the reference point. The return to normal is detected by the thermoreceptors. The removal of the stimulus will stop the homeostatic action.
Iodine test, Benedict's test and ethanol-emulsion test procedures.
Iodine test:
Add a few drops of iodine solution (KI solution) to the test sample in a test tube or on a white tile
Observe any colour change
If starch is present, the yellow-brown solution will turn blue-black.
This is because the iodine takes up position in the centre of the amylose helix to form a dark blue starch-iodide complex.
If starch is absent, the solution remains yellow-brown.
Benedict's test:
All monosaccharides and some disaccharides are reducing sugars, with the exception of sucrose(table sugar)
Benedict's test makes use of the ability of reducing sugars to reduce copper from a valency of 2 to 1. It involves the use of an alkaline solution of copper (II) sulfate which is reduced to insoluble copper (I) oxide which is a brick red precipitate.
To 2cm3 of the test sample in a test tube, add an equal volume of Benedict’s solution.
Mix well and place the test tube in a boiling water bath for 2min
Observe any colour change.
Benedict’s test is semi-quantitative. The greater the amount of reducing sugar, the greater the amount of brick-red precipitate formed. Hence, the greater the intensity of red in the final mixture.
If there is no reducing sugar present, the solution remains blue in colour.
If there is reducing sugar present, the solution turns from blue to green/yellow/brown/brick red
Ethanol-emulsion test:
Lipids are readily soluble in organic solvents like ethanol but not in water. Therefore, white emulsions are formed during mixing.
If the test substance is a solid, grind it first before adding ethanol. Allow any solid particles to settle
Add 2cm3 of ethanol to 2 drops of the test substance in the test tube. Mix well.
Decant the ethanol into another test tube containing 2cm3 of water
Mix well and observe for cloudiness
If the test substance contains lipids, a homogeneous/clear solution is formed with ethanol and white emulsion is formed when water is added.
If the test substance does not contain lipids, a homogeneous/clear mixture is formed with ethanol and the solution remains homogeneous/clear when water is added.
Homeostatic – soluble proteins in blood plasma act as buffers, stabilising the pH
Enzymatic – All chemical reactions occuring in the cell are catalysed by specific enzymes (refer to Chapter 3). These enzymes speed up the rate of reactions
Hormonal – some proteins function as hormones in the body e.g. insulin and glucagon (refer to Topic 8)
Transport – proteins present in plasma membranes function in transport of certain substances into and out of the cell/membrane bound organelle. Haemoglobin functions in the transport of oxygen in vertebrates and lipoproteins function in the transport of cholesterol in blood
Storage – the protein ferritin functions to store iron in the liver. Myoglobin present in skeletal muscle cells, functions to store oxygen
Protection – antibodies function as part of the immune system (refer to Chapter 4). Blood clotting factors e.g. fibrinogen and thrombin (refer to Chapter 5) are important in the blood clotting mechanism.
Support/structural – collagen is a component of connective tissues, cartilage, tendons and ligaments. Keratin is present in hair, hoofs and feathers
Source of energy – proteins act as a source of energy during extreme starvation, when carbohydrate and fat reserves are depleted.
Influenza
Viral disease e.g. influenza
3 types of influenza (type A, B and C virus)
Influenza has a membranous envelope containing projections made of protein
These spike proteins play an important role in attaching onto a cell, allowing it to gain entry into the host cell.
Epithelial cells lining the lungs take in the viruses via endocytosis
Influenza can spread by droplet infection
When a person has contact with a contaminated surface and subsequently touches his or her own mouth, nose or eyes
Following infection, influenza has an incubation period of about 1 day
The signs and symptoms of influenza or flu usually include a high fever between 39 degrees celsius and 41 degree celsius, sore throat, congestion, dry cough and headache
Fever and the lack of excessive mucus production distinguishes flu from a common cold
Having the signs and symptoms of influenza or flu is sufficient for an initial diagnosis of influenza. Laboratory tests such as antigen detection tests and molecular assays can make the chances of detecting influenza higher.
To treat influenza, antiviral drugs that inhibit neuraminidase, blocking the release of virions from infected cells can be used.Antihistamines and pain relievers alleviate the symptoms of the influenza.
Immunisation with vaccines that contain several antigens at once can be used as a preventive measure against influenza.
Features of a dialysis machine
Tubing in the dialyser is long, narrow and coiled. It increases the surface area to volume ratio to speed up the exchange of substances between the blood and the dialysis fluid
Dialysis fluid contains no metabolic waste products and has the same concentration of essential nutrients such as glucose, amino acids and essential salts as that of healthy blood. This is because a steep concentration gradient exists which allows nitrogenous waste products e.g. urea, uric acid, creatinine and excess water and mineral salts to diffuse out of the tubing into the dialysis fluid. The waste products are removed from the blood. This maintains the correct solute composition and water potential of the blood. This also ensures that such substances do not diffuse out of the patient’s blood into the dialysis fluid. Furthermore, if the patient’s blood lacks any of these essential nutrients, it will diffuse from the dialysis fluid into the patient’s blood in the tubing
Direction of blood flow in the tubing is opposite to the flow of the dialysis fluid. This maintains a concentration gradient between the patient’s blood and the dialysis fluid for the removal of metabolic waste products
Define voluntary action and explain what happens when we want to pick up a pencil with our hands.
(A voluntary action is an action under the _____ of a _____. When we want to pick up a pencil with our hands, our _____ see the pencil. A ________ is sent to the ______. Our _____ calculates the position of the pencil and predicts how we should move our ______. The ______ then sends an _____ along the ________ neuron in our _____ to the appropriate motor neurons. This ______________ is sent to the ______, i.e. the appropriate _________ in our arm. The muscles _________ and we pick up the pencil.)
A voluntary action is an action under the control of a will. When we want to pick up a pencil with our hands, our eyes see the pencil. A nerve impulse is sent to the brain. Our brain calculates the position of the pencil and predicts how we should move our arm. The brain then sends an impulse along the relay neuron in our spinal cord to the appropriate motor neurons. This nervous impulse is sent to the effector, i.e. the appropriate muscles in our arm. The muscles contract and we pick up the pencil.