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BIOLOGY TOPIC 2 MOLECULAR BIOLOGY

biological molecules


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BIOLOGY TOPIC 2 MOLECULAR BIOLOGY


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[Front]


Biological processes are regulated by?
[Back]


enzymes

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BIOLOGY TOPIC 2 MOLECULAR BIOLOGY - Detalles

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What is molecular biology?
Focuses on biological activity at a molecular level which includes the structure and function of chemical substances
What is an organic compound?
Compound that has carbon and is found in living things
Why is carbon the basis of organic life?
It can form large and complex molecules by covalent bonding
How does a structure of a carbon atom allow it to form bonds?
Can share 4 electrons to form 4 covalent bonds
What are the 4 principle groups of organic compounds?
Carbohydrates lipids nucleic acids proteins
What are exceptions of carbon that aren't considered to be an organic compound?
Carbides (CaC2) Carbonates (CO3 2-) Oxides of carbon (CO, CO2) Cyanides (CN-)
How many bonds do carbon atoms form?
4 covalent bonds with very stable bonds between carbon atoms (catenation)
What are carbohydrates? (4)
Made up of C, H, O atoms = (CH2O)n energy source and a short term energy storage recognition molecule (glycoproteins) structural component (part of DNA / RNA )
What are Lipids? (5)
Non-polar, hydrophobic molecules simple, complex or derived forms makes up cell membranes (phospholipids and cholesterol) long term energy storage (fats and oils) signalling molecule (steroids)
What are nucleic acids?
Genetic material of all cells for the inherited features of an organism DNA: code for protein making RNA: helps make proteins
What are proteins?
Made up of C, H O, N (some S) regulatory molecules in catalysis all enzymes are proteins structural molecule cellular signalling (transduction pathways)
What are monomers? (3)
Small, recurring subunits that make complex macromolecules Carbohydrates, nucleic acids + proteins are made of subunits= larger polymers lipids DO NOT contain recurring monomers
What are the subunits of carbohydrates?
Recurring monomers: monosaccharides => disaccharides => polysaccharides form ring structures linked with condensation reactions with water as a byproduct
What is lipids made up of?
Fatty acids and glycerol differ in structure so they don't contain a common recurring monomer triglycerides, phospholipids and waxes contain fatty acids chains
What are fatty acids?
Long chains of hydrocarbons that may or may not have double bonds (unsaturated vs saturated)
What are proteins made up of?
Amino acids which join to form polypeptide chains each amino acid has an amine group (NH2) carboxyl group (COOH) R = different properties (polar / non-polar)
What are nucleic acids made up of?
Made up of nucleotides which form polynucleotide chains has: pentose sugar, phosphate group and a nitrogenous base sugar differs in RNA and DNA
What are polymers of glucose?
Glycogen (granules) cellulose (cell wall) starch (granules)
What are the three main classes of lipids?
Simple (neutral) lipids compound lipids derived lipids
What are simple (neutral) lipids?
Esters of fatty acids and alcohol (triglycerides and waxes)
What are compound lipids?
Esters of fatty acids, alcohol and additional groups (phospholipids and glycolipids)
What are derived lipids?
Substances from simple / compound lipids (steroids and carotenoids)
How do proteins join together?
Amino acids join with peptide bonds between the amine and carboxyl groups of amino acids creates a dipeptide = polypeptide chain chain folding depends on the amino acid order
How do nucleic acids bond together?
Nucleotides form bonds between the pentose sugar and phosphate group = long polynucleotide chains 2 complementary base pairs bond with hydrogen bonds to form double strands twists = double helix structure
What is vitalism?
A belief that said organic molecules can only be made by living systems
Why did they believe that only living things could make organic molecules?
Living things has a "vital force" organic compounds were thought to have a non-physical element which inorganic molecules don't have
How did the vitalism theory get disproven?
They found that organic molecules could be artificially made heated an inorganic salt (ammonium cyanate) = urea urea is a waste product of nitrogen metabolism and is removed from the kidneys artificial synthesis = organic molecules aren't fundamentally different to inorganic molecules
What is metabolism?
The web of all the enzyme catalysed reactions in a cell or organism
What do metabolic reactions do?
Provide energy for cellular processes (eg: growth) start the synthesis and assimilation of new materials for use within the cell
What is anabolism?
Building up complex molecules from simple molecules by condensation reactions eg: when monomers are covalently joined = water is a byproduct
What are monosaccharides joined with?
Glycosidic linkages = disaccharides
How is triglycerides formed (what type of linkage)?
Glycerol + fatty acids joined with ester linkage
How are nucleotides joined together?
Phosphodiester bonds = polynucleotide chains
How are amino acids joined?
With peptide bonds to make polypeptide chains
What is catabolism?
Breakdown of complex molecules into simpler molecules by hydrolysis reactions needs water molecules to break bonds within the polymers releases energy oxidation reactions
Why are the electrons in H2O not shared equally?
Because oxygen has a higher electronegativity = attracts the electrons more strongly electrons orbit closer to the oxygen atom = polarity =permanent dipole
Why is water polar?
Because of the slight charge difference across the different poles oxygen is slightly negative hydrogen atoms are slightly positive
What does the charge difference allow water to do?
Form weak polar associations with other polar molecules slightly negative attracts the slightly positive poles of other molecules vice versa
When does a hydrogen bond form?
When the slightly positive hydrogen from H2O is attracted to a slightly negative F, O, N atom of another molecule
Why are hydrogen bonds stronger than other polar associations?
Because of the high electronegativity of F, O and N
How does water bond with other water molecules?
Between a + hydrogen and a - oxygen of two molecules
What gives water its special properties?
The intermolecular bonding between water molecules
Why can water absorb so much heat before changing state?
Because of extensive hydrogen bonding between water molecules H-bonds need to be broken = needs heat energy
What are the 3 properties of water?
Thermal properties - water can absorb a lot of heat before changing state because breaking the hydrogen bonds is needed cohesive / adhesive properties - water sticks to other water molecules (cohesion) and charged substances (adhesion) Solvent properties - water dissolves polar and ionic substances = competing polar associations to draw materials apart
Why is water a good place for living organisms?
Temperature changes slowly = maintenance of constant conditions
Comparing Methane (CH4) with water
H20 weight = 18 dalton CH4 weight = 16 dalton both have tetrahedral orbital forms but water is bent because of unbonded electron pairs
What is sweating?
Evaporation of water to cool down
How does sweating work? (4)
Change of water from liquid = vapour needs energy energy comes from the skin's surface when its hot when water evaporates skin is cooled because water has a high SHC = absorbs a lot of thermal energy before evaporating water - highly effective coolant
What are the cohesive properties of water?
Same molecules stick together forms hydrogen bonds w other water molecules
What are the adhesive properties of water?
Different molecules stick together by forming intermolecular associations with polar and charged molecules
How does the cohesive properties explain surface tension?
Hydrogen bonding between water molecules helps the liquid to resist low levels of external force makes the water dense enough for small organisms to move along its surface
How does the adhesive properties explain the capillary action?
Attraction to charged or polar surfaces makes water to flow against gravity = capillary action needed for water to be transported up plant stems by transpiration
Why can water dissolve so many substances?
Can dissolve any substance that has charged particles (ions) or electronegative atoms (polarity) because the polar attraction of a large amount of water molecules = weaken intramolecular forces (ionic) = disassociation
How does hydration occur?
Slightly charged regions of the hydrogen atoms and the oxygen atoms surround atoms with an opposing charge = forms dispersive hydration shells
What does hydrophilic mean?
Substances that freely associate and readily dissolve in water all polar molecules and ions
What does hydrophobic mean?
Substances that don't dfeely associate or dissolve in water large non polar molecules (fats and oils)
What are water soluble substances that travel in our body?
Sodium chloride (NaCl): ionic transported in blood Oxygen: small amounts are soluble in water transported in haemoglobin in red blood cells Glucose: hydroxyl groups (-OH) associates with water so it travels in the blood Amino Acids: transported in an ionized state (either amine or carboxyl group is charged)
What are water insoluble substances that travel in our body?
Lipids (fats and cholesterol): non polar and hydrophobic so it does not dissolve in water form complexes with proteins (lipoproteins) = to go through bloodstream hydrophilic parts of proteins, cholesterol and phospholipids shield internal hydrophobic parts
What are some examples of monosaccharides (one sugar unit)
Glucose, galactose and fructose usually sweet tasting and is an immediate energy source for cells
What are some examples of disaccharides (2 sugar units)
Lactose, sucrose and maltose small enough to be water soluble, transport form of carbohydrates
What are some examples of polysaccharides?
Cellulose glycogen and starch used for energy storage or cell structure
What does the type of polymer formed depend upon?
Monosaccharide subunits bonding arrangement between them
What is cellulose? (3 + 2 examples)
Polysaccharide (structural) found in the cell wall of plants linear molecule made of beta glucose in a 1-4 arrangement b glucose is indigestable to most animals as they lack the enzyme to break it down eg: cows (ruminants) digest cellulose because of bacteria in a specialized stomach eg: rabbits (caecotrophs) will reingest specialized feces that have digested cellulose
What is starch (mention amylose)
Polysaccharide (energy storage) in plants a glucose in a 1-4 arrangement found as amylose or amylopectin Amylose is a linear (helical) molecule Amylopectin is branched with 1-6 linkages added amylose is harder to digest and is less soluble = but it takes up less space so it is a better storage form
What is glycogen? (3)
Energy storage polysaccharide in the liver made of a glucose linked with 1-4 and 1-6 (branching) similiar to amylopectin because of branching
What are fatty acids?
Long hydrocarbon chains in certain lipids (triglycerides and phospholipids) hydrocarbon chain LENGTH can differ and number of DOUBLE BONDS
What are saturated fatty acids?
They have no double bonds (max number of H atoms) linear from animal sources (fat) solid at room temp
What are unsaturated fatty acids? (level up)
They HAVE DOUBLE BONDS monosaturated = 1 double bond polysaturated = more than1 double bond bent from plant sources (pols) liquid at room temp
What are cis isomers?
Hydrogen atoms attach to the carbon double bond are on the same side
What are trans isomers?
Hydrogen atoms attached to the carbon double bond are on different sides
Where do TRANS fatty acids come from? (transgender)
Don't happen naturally but are produced by an INDUSTRIAL PROCESS called hydrogenation linear even though they are unsaturated solid at room temp
What are triglycerides?
Long term energy storage animals store them as fats (solids) plants store them as oils (liquids) formed when condensation reactions happen between 1 GLYCEROL AND 3 FATTY ACIDS
Explain the formation of a triglyceride
Condensation reaction between 1 glycerol and 3 fatty acids hydroxyl group of glycerol joins with the carboxyl group of the fatty acids = ester linkage produces 3 molecules of water can be saturated or unsaturated = depends on the composition of teh fatty acid chain
How is fat and cholesterol transported and why are they transported this way?
Because they can't dissolve in blood they are packaged with proteins = lipoproteins for transport
What do low density lipoproteins do (LDLs)>
Carries cholesterol form the liver to the body = raises cholesterol levels - bad
What do high density lipoproteins do (HDL)?
Carry excess cholesterol back to the liver for disposal = lowers cholesterol levels
How does a high intake of the different types of fat affect cholesterol levels?
Saturated fats = increase LDL levels = raises blood cholesterol Trans fats = increase LDL levels AND decreases HDL levels = raises blood cholesterol ALOT Unsaturated (cis) fats = increase HDL levels = lowers blood cholesterol
What does high cholesterol lead to?
Hardening and narrowing of arteries (artherosclerosis) high levels of LDL = LDL particles forms deposits in the walls fat accumulation = development of plaque which reduces blood flow Coronary Arteries become blocked = CHD which causes heart attacks and strokes
What are the two main health claims about lipids in diet?
Diets with too much saturated and trans fats = increase in CHD risk Diets with a lot of mono unsat and poly unsat (cis) = decrease CHD risk
What is some evidence that supports that saturated and trans fats increase the risk of CHD?
Positive correlation with intake of sat fats and CHD in people BUT some populations don't fit this ( maasai tribe have a fat rich diet but low rates of CHD) Intervention studies show that lowering sat fat intake reduces factors = CHD development (BP) BUT study's validity depends on sample size and study duration
What is some evidence that goes against that saturated and trans fats increase the risk of CHD?
Amount of sat and rans fats in western diets have reduces over last 50 years but CHD cases increases BUT increased carbs causes detrimental health effects as well (eg: diabetes) ALSO CHD depends on other factors as well like exercise
Differences in energy storages of carbs and lipids (5)
Storage CARB: short term energy storage LIPID: long term energy storage Osmotic effect CARB: more effect on cell LIPID: less effect on cell Digestion CARB: easily digested LIPID: harder to digest ATP Yield: CARB: stores half as much ATP per gram LIPID: stores 2x as muc ATP per gram Solubility CARB: water soluble as monomers - easy to transport LIPID: not water soluble (hydrophobic) - difficult to transport
How is ATP made?
Energy made with cell respiration and can be used in metabolism
What is BMI?
Body mass index measures relative mass based on weight and height to see potential weight problems in sedentary adults
How is BMI calculated?
BMI = mass in kg / (height in m)2 squared
Who are the BMI not accurate for?
Pregnant women professional athletes as they have unrepresentative muscle/ fat ratios used with other measurements SHOULD NOT BE used as a diagnostic tool
How many amino acids are there and where are they made?
20 different amino acids in polypeptides synthesised on ribosomes by translation
How do the different amino acids differ so much? (in structure)
The variable side chain (R) has distinct chemical properties (eg: charged) the protein folds and works differently according to its position in the polypeptide chain
How are amino acids joined together?
Covalently linked by PEPTIDE BONDS which are formed by condensation reactions = water molecules formed as a byproduct