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carbohydrates protein amino acidslipids fats
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CHEMICAL COMPOSITION OF THE CELL
1. 4 major organic compounds of living systems:a. Carbohydratesb. Protein c. Lipidsd. Nucleic acid
2. Composed of C, H, O and N, additional elements: phosphorus (P), iron (Fe), magnesium (Mg), sodium (Na), potassium (K), iodine (I) and calcium (Cl).
Importance of organic compounds in the cell
1. 15% of protoplasm is made up of proteins.a. Building blocks of protein are amino acids
2. Carbohydrates are the major source of energy in cell.3. Lipids make up 15% of protoplasm 4. Nucleic acids are the complex macromolecules which store genetic information (DNA).
a. Nucleotide is the building blocks of nucleic acid
Importance of water in cell
1. Solvent a. Water is a polar molecule with an unequal distribution of charges b. Polar molecules attract one another plus ion c. Water dissolves many organic compounds
2. Transport medium a. Water is the main constituent of blood and body fluid b. Blood plasma contains and transport nutrients, respiratory gases and hormonesc. Waste products (urea, creatinine) are excreted from body through urine
3. Medium for biochemical reaction a. Digestive reaction such as hydrolysis of proteins, lipids and carbohydrates
4. Maintain stable internal environmenta. Concentration of water and inorganic salts that dissolve in water is important in
maintaining osmotic balance between blood and interstitial fluid 5. Lubrication
a. Mucus is composed of water, assists the movement of food substances in digestive tract
b. Synovial fluid in joint help to lubricate the joint when the joint is bend 6. High cohesion and adhesion force
a. Water molecules tend to stick to one another and move along in long unbroken columns through xylem vessel in plants
7. Maintain constant body temperaturea. High specific heat capacity
i. Water absorb a lot of heat from muscles or environment before temperature rises
ii. Prevent the body temperature rising too fast b. High latent heat vaporization
i. Helps to lower body temperature when sweating ii. When sweat is evaporating, it absorbs heat from skin and cools our body
CARBOHYDRATES
1. Common carbohydrates are starch and cellulose.2. Both are macromolecules with high molecular weights.3. Both are polymers (polysaccharides), built from repeating units of monomers (glucose).
A. Monosaccharides
C₆H₁₂O₆ (hexose)1. Simplest form of carbohydrates.
a. Glucose: immediate source of energy for cellular respiration b. Galactose: sugar in milk and yogurt
c. Fructose: sugar found in honey 2. Same molecular formula but different atoms arrangement.
a. Structural isomers: substances with identical molecular formulas but different structural formulas
B. Disaccharides 1. Made up of 2 monosaccharides combined together 2. 3 common disaccharides:
a. Maltosei. Product of partial digestion of starch
b. Sucrose i. Table sugar
ii. Found in sugar cane, sugar beet and sweet fruits c. Lactose
i. Sugar in milk 3. All sugars are soluble in water because of their hydroxyl group4. Glycosidic bond – linkage between sugar molecules 5. All monosaccharides and dissacharides are reducing sugar, except sucrose
C. Polysaccharides 1. Made up of chains of monosaccharides which are linked together by glycosidic bonds.2. Polysaccharides tend to be very large and branched.
a. Insoluble in water and amorphous (shapeless)3. General formula Cn(H₂O)n n is 200-25004. Most polysaccharides are starch, glycogen and cellulose. 5. Starch:
a. Glucose polymer b. Insoluble in waterc. Store as glucose in plant cell d. Digested by enzyme amylase e. 2 types of molecules
i. Amylose: linear, unbranched chains of several hundred glucose residues, coiled helically into compact shape
ii. Amylopectin: compact and highly branched
6. Glycogen:a. Store as glucose in animal cell b. Structure of glycogen is similar to that of amylopectin, branches in glycogen:
shorter and more frequent c. Glycogen is broken down into glucose when energy is needed d. Liver and skeletal muscle are major depots of glycogen
7. Cellulose a. Forms most structural components in plants b. Wood is largely cellulose while cotton and paper are pure cellulose c. Absence of side chains allow linear molecules to lie close together d. OH project out from each chain, forming hydrogen bonds with neighbouring
chains: creates rigid cross-linking between the chains, making cellulose a strong support material.
e. Fully permeable to water and solute
CONDENSATION AND HYDROLYSIS
1. Condensation of monosaccharides
2. Hydrolysis: chemical reaction that breaks up large molecules by adding water to them. Hydrolysis of dissacharides
REDUCING SUGAR AND NON-REDUCING SUGAR
1. Chemical test for disaccharides:a. Reducing sugar can be tested by Benedict’s solution b. When reducing sugar is boiled with benedict’s solution, brick red precipitate is
produced. c. Presence of sucrose can be detected by breaking down sucrose into glucose and
fructose via hydrolysis (heating sucrose with dilute HCl), followed by heating glucose/fructose with Benedict’s solution.
d. Brick red precipitate is formed indicates the presence of reducing sugar
2. Reducing sugars can act as reducing agentsa. Reducing sugar contain aldehyde groups are oxidised to carboxylic acids b. Reduce the Cu²⁺ to Cu⁺ which forms as red precipitate, copper (I) oxide
PROTEINS
1. Proteins are polymers. The monomers of proteins are amino acids. 2. All amino acids have same basic structure.
3. Essential amino acids can be found in meat. 4. Types of amino acids:
5. Amino acids can be joined together forming peptide bonds. 6. Condensation reaction forms covalent bond between monomers, amino group and acid
group of another. a. 2 amino acids join together to form dipeptide molecule
Protein structure
1. Primary structure i. Linear arrangement of amino acids in a protein
2. Secondary structure i. Polypeptides chains are folded into different shape ii. Example: α-helix and β-pleated sheets iii. Held together by hydrogen bonds: giving the shape and stability
3. Tertiary structure i. 3D structured protein ii. Large number of non-covalent interactions between amino acids
a. Disulphide bonds: strong double bond (S=S) is formed between sulphur and atoms
b. Ionic bonds: forms between 2 oppositely charged ‘R’ groupsc. Hydrogen bonds: hydrophobic and hydrophilic interactions
iii. Can be broken down by heat a. Increase of kinetic energy of protein molecules, vibrate more, bonds will
breakb. Protein loses its shape and denaturedc. Do not reform to original shape when cold
4. Proteins with 3D structure:i. Globular
a. Ball-like structures where hydrophobic parts are towards centre and hydrophilic parts towards the edge (water soluble)
b. Haemoglobin is water soluble globular protein 1. composed of 2 α-polypeptide chains, 2 β-polypeptide chains and
inorganic prosthetic group 2. haemoglobin carries oxygen around in blood 3. O₂ molecules bind to Fe²⁺ ion in heme group
ii. Fibrous a. Long fibres and insoluble in water b. Collagen in bone, cartilage, keratin (fingernails and hair)
5. Quaternary structure i. 2 or more polypeptide chains joined together
LIPIDS
1. Lipid consists of carbon, hydrogen and oxygen 2. Types of lipids:
a. Oilb. Fats c. Phospholipidd. Waxes e. Steroids
3. Fats and oils are triglyceride 4. Triglyceride is an ester that formed through condensation of one molecule of glycerol and 3
molecules of fatty acid.
5. Types and functions of lipids:
Lipids functions Triglycerides
- True fats - Good energy store - Cover many organs to provide physical
protection - Stored under skin as heat insulator - Transport fat-soluble vitamins (ADEK)
Phospholipids - Composed of diglyceride that bonded
to phosphate group
- Abundant lipids in plasma membrane - Control cell permeability
Waxes - Insoluble
Forms waterproof layer of cuticle on:- epidermis of plants (prevent water loss)- exoskeleton of insects (prevent water
loss)- feathers of birds (waterproof)- fur of mammals (waterproof)- sebum (oil, secreted by skin) to soften
the skin Steroids
- cholesterol - sex hormones - bile
- makes the plasma membrane more rigid and stable
- testosterone, oestrogen, progesterone: controls sexual development and body physiology
- emulsifies fat
6. Lipids are insoluble in water but soluble in organic solvents (alcohol, acetone).
Saturated fats Differences Unsaturated fats Only single bond present between carbon atoms
Presence of double bonds between carbon atoms and
fatty acids
At least double bond between carbon atoms
Difficult to react with additional hydrogen atom
Ability to react with an additional hydrogen atom
Easily react (double bond present)
Solid (high melting point) Condition at room temp Liquid (low melting point)Stearic acid (facial wash) Examples Oleic acid (vege oil)
ENZYMES
1. Enzymes are biological catalyst that increase the rate of metabolic reactions. 2. Enzymes are globular proteins with specific tertiary shape. 3. Reaction of enzymes are specific to specific reaction which depends on the shape of the
substrate. 4. Active site of enzyme acts as catalyst which the shape is complementary to the substrate. 5. In enzyme reaction, substrate is turned into product. 6. Example of enzymes:
a. Lactase: breaks down lactose into glucose and galactoseb. Catalase: breaks hydrogen peroxide into water and oxygen
Extracellular enzymes:
- Enzymes that have been secreted and used outside the cell - Cellulase: hydrolyses cellulose into glucose - Amylase: hydrolyses starch (amylose) into maltose
Intracellular enzymes:
- Enzymes that have been synthesized and used within the cell - DNA/RNA polymerase: synthesize DNA/RNA- Carbonic anhydrase: aids in the conversion of carbon dioxide to carbonic acid and
bicarbonate ions
7. Most reactions in cell require very high temperature to get going which destroy the cell. 8. Enzymes work by lowering the activation energy of reaction.
a. Activation energy: energy required to start a reaction
Explain the mechanism of lock and key hypothesis
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9. Characteristics of enzymes:a. Enzymes are protein b. Biological catalyst which speed up the rate of biochemical reactions c. Not destroyed at the end of reaction d. Enzyme controlled reaction is catalyst reversible reaction e. Sensitive to changes in temperature, very active at optimum temperature.
Denatured at high temperature. f. Sensitive to change in pHg. Specific, one type of enzyme can catalysed only one type of substrate
Factors affecting enzyme activity
A) Temperature 1. Increase in temperature increases kinetic energy of molecules. Increase in random collisions
between enzyme molecules and substrate molecules. Increase the rate of reaction, forming more product.
2. As temperature increases, weaker hydrogen and ionic bonds will break. Breaking of bonds within enzyme caused the change in shape of active site. Enzymes are denatured and no longer function. Rate of reaction decreases.
B) pH1. Lower pH means higher [H⁺] and lower [OH⁻].2. H⁺ and OH⁻ interfere with hydrogen and ionic bods that hold an enzyme. Change in shape of
enzyme, especially the active site. 3. Different enzymes have optimum rate of reaction at different pH values4. Extreme changes in pH causes the enzyme to denature.
C) Substrate concentration 1. Limiting factor: stops a reaction from proceeding at higher rate. 2. Rate of reaction of enzymes increase with the increase of substrate which any further
increase produces no significant change in reaction rate. 3. Active sites of enzymes are saturated with substrate. 4. Enzyme-substrate complex has to dissociate before the active sites are free to
accommodate more substrate. 5. Substrate is high and temperature and pH are constant, rate of reaction is proportional to
enzyme.
D) Enzyme concentration 1. At low enzyme concentrations, adding more enzyme increases rate of reaction. More
enzymes is more likely to bind with substrate. 2. At high enzyme concentrations, adding more enzymes has no effect on reaction rate. Rate of
reaction becomes constant and enzyme concentration is no longer a limiting factor.
Uses of enzyme in daily life and industry
Enzymes Uses Type of industry/application α-Amylase Converts starch flour into
sugar in making of bread or dough
Baking industry
Amylase Removes starch that is used as stiffeners in fabrics
Textile products
Amylase and amyloglucoxidase Change starch to sugar in the making of syrup
Starch products
Protease, lipase and amylase Dissolve protein, oil, starch stains on clothes
Biological washing powder or detergents
Protease and protease papain Tenderises meat Food processing and meat industry
Protease Removes the skin of fish Remove cloudiness during storage of beer
Fish productsBrewing industry
Zymase (produced by yeast) Converts sugar into ethanol Alcoholic beverages (brewing industry)
Lipase Ripening of cheese Dairy industry Rennin Coagulate milk protein Dairy industry (making yogurt)Lactase Hydrolyses lactose to glucose
and galactoseMaking of ice cream
Cellulose Breaks down cellulose and remove seed coat from cereal grains Extracts agar from seaweed
Cereal grain products Seaweed products
Trypsin Removal of hair from animal hides Removes blood clots and clean wounds
Leather products Medical analysis
Pancreatic trypsin Microbial trypsin
Treats inflammation Dissolves blood clots
Medical/pharmaceutical products
Glucose isomerase Production of high fructose syrup:Glucose is converted into fructose. Fructose is sweeter than glucose which widely used in slimming products
Explain how enzymes act in:
1. Helping to cook meat 2. Extracting agar from seweed3. Making fresh yogurt 4. Production of variety of cheese
Importance of chemical composition in cells
1. Carbohydratesa. Glucose is oxidised to produce energy in cell metabolism
b. Starch is the food stored in plant cellsc. Glycogen is the food stored in animal cells d. Cellulose makes up the cell wall of plant cells
2. Proteins a. Enzymes act as biological catalyst which increase the rates of reactions in cellsb. Antibodies are produced by WBC to destroy foreign bodies c. Some hormones are protein: insulin which produced in pancreas, oestrogen and
testosterone. Stimulate functions of certain organs d. Respiratory pigment: Hb, carries oxygen in the red blood cells
3. Lipids a. Provide the most energy b. Fat stored in adipose tissues under the skin keeps body heat: heat insulator,
protection to organs c. Acts as solvent for vitamins ADEKd. Phospholipid is the main component of cell membrane e. Cuticle on leaves surface and stems prevents excessive water loss from plants f. Steroid: cholesterol maintains the structure of plasma membrane
4. Watera. Acts as transport medium b. Medium for biochemical reaction c. Solvent d. Supplies hydrogen and oxygen for reaction in cell e. Gives support in herbs f. Helps to control the temperatures of animal bodies
5. Nucleic acid a. Deoxyribonucleic acids (DNA) is the main part of chromosomes b. DNA forms genetic material of the cellc. Ribonucleic acids (RNA) plays important role in protein synthesis d. RNA forms genetic material in some virus
6. Nucleotides are small organic molecules 7. Each nucleotide has 5-carbon sugar (ribose or deoxyribose), nitrogen-containing base (single
or double ringed) and phosphate group.
8. Nucleic acids DNA and RNA a. Four different types of nucleotides are bonded together in large macromolecule b. RNA is single-stranded: functions in assembly of proteins c. DNA is double stranded (polynucleotides): genetic messages are encoded in its base
sequence
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