Chapter 3 - Biological Molecules Flashcards
Carbohydrates (polymers)
Carbon, Oxygen, Hydrogen
➜ provides energy and build body structures
➜ Formula: Cx(H2O)y
Lipids
Carbon, Hydrogen, Oxygen
➜ insoluble in water
➜ soluble in alcohol
Proteins
Carbon, Hydrogen, Oxygen, Nitrogen, Sulfur (usually but not all)
Nucleic acid
Carbon, Hydrogen, Oxygen, Nitrogen, Phosphorus
- made of nucleotide monomers and phosphodiester bonds between monomers
- consist of phosphate group between pentose molecules forming BACKBONE
- in DNA hydrogen bonding between 2 antiparallel strands causing double helix shape
Water
➜ Polar - acts as solvent for ions
➜ Cohesion (between H20 mol) - water drawn up xylem
& Adhesion (H bond to other molecules) - capillary action
➜ Doesn’t change state (high specific heat capacity) - constant temp
➜ Surface tension - allows insects to live on water
➜ Ice less dense - habitat due to H bonding so ice floats and provides a habitat
➜ High latent heat of vaporisation - acts as a coolant- due to H bonds
➜ ice insulates water below
➜ transparent so plants under surface can photosynthesis as light penetrates
➜ Incompressible - can prevent plants from wilting & act as a hydrostatic skeleton for invertebrates
Ribose
Carbon, Oxygen, Hydrogen
➜ carbohydrate - pentose monosaccharide
Glucose
➜ carbohydrate - hexose (6C) monosaccharide
Alpha - down OH
Beta - Up OH
➜ soluble - easily transported
➜ chem bonds = lots of energy
Condensation
➜ Bond formed between H atom on one monosaccharide (glucose) and OH hydroxyl group on other mono (glucose) releasing WATER
- molecule of water released during the reaction
➜ Covalent bond = Glycosidic bond
➜ Allows monosaccharides to make polysaccharides
Amylose
➜ alpha glucose in 1, 4 glycosidic bonds - long and unbranched
➜ coiled shape formed with hydrogen bonds - causes it to be compact -> good for storage - more fits in less space
➜ less soluble than the glucose used to make it
Amylopectin
➜ alpha glucose in between 1,4 glycosidic bond - long branched
➜ some glycosidc bond between 1,6 carbon
➜ side branches allow enzymes to break down molecule to get to glycosidic bond quickly = glucose released quickly
➜ insoluble
Hydrolysis
➜ glucose is released for respiration from starch or glycogen
➜ allows polysaccharides break apart
➜ molecule of water added
Monosaccharides
➜ Formula: (CH2O)n
➜ n = 3 triose
n = 5 pentose
n = 6 hexose
Disaccharide
➜ 2 mono..
• glucose + glucose ➜ maltose
• glucose + galactose ➜ lactose
• glucose + fructose ➜ sucrose
➜ formed via glycosidic bonds
Cellulose
➜ 1,4 bonds - Beta glucose joined together
➜ Alternate beta glucose molecule is flipped upside down
➜ straight chain
➜ Cellulose make H bonds with each other forming microfibrils
Reducing Sugar Test
• Add Benedict’s
• becomes brick red from blue
Non reducing sugar test
➜ Benedict’s Solution:
• Boil with HCL
• Neutralise with sodium hydrogen carbonate
• Add benedicts
• becomes brick red
➜ Reducing sugar has become hydrolysed
Starch test
➜ Iodine is added to solution
➜ Positive test = yellow/brown to purple/black
Lipid test
➜ Sample mixed with alcohol
➜ Mixed with water and shaken
➜ Positive test = white emulsion layer formed on top of solution
Triglycerides
➜ type of lipid
➜ One glycerol molecule and 3 fatty acids
➜ Synthesis of triglyceride from glycerol and 3 fatty acids by the formation of ester bonds, producing 3 water molecules - condensation reaction
➜ insoluble - prevent water entering cell via osmosis
Saturated fatty acids
No double bonds
eg butter
Unsaturated fatty acids
➜ One double bond = monosaturated
➜ More than one double bond = polyunsaturated
➜ Presence of double bond causes molecule to bend
➜ Therefore, liquid at room temp
Phospholipid
➜ Contain phosphorus
• modified triglyceride
➜ One fatty acid replaced with phosphate group
➜ Phosphate group = hydrophilic head = polar
➜ Fatty acid chain = hydrophobic tail = non polar
Surfactants
➜ Surface active agents
• phospholipids form a layer on surface of water with phosphate heads in water and fatty acid tails sticking out of the water
Sterols
➜ Steroid alcohols
Cholesterol
➜ Sterol
➜ Manufactured in liver and intestines
➜ Regulates fluidity of membrane
• Stops phospholipids grouping and crystallising which reduces permeability
➜ Adds stability without making cell too rigid
➜ Has hydrophobic and hydrophilic end
Biological roles of Lipids
hormone production
electrical insulation
thermal insulation
water proofing
Primary Structure of Proteins
Sequence of amino acids in a polypeptide chain
Secondary Structure of Proteins
➜ Coil into Alpha helix or Beta pleated sheets form as a result of hydrogen bonding between different amino acids
Tertiary Structure of Proteins
Contain:
➜ hydrogen bonding
➜ Ionic bonding
➜ Disulphide bonds
➜ London forces
➜ final 3D structure of proteins with 1 polypeptide chain
Quaternary Structure of Proteins
Final 3D structure of proteins with more than 1 polypeptide
Globular protein
➜ compact, water soluble and spherical in shape
➜ 3D tertiary structure
➜ temp and pH sensitive
➜ Hydrophilic R groups on outside of protein - soluble in water
➜ insulin - hormone
➜ haemoglobin - transport O2
➜ fibrinogen - used in blood clotting
➜ amylase(enzymes) - catalyse reactions
Conjugated proteins
➜ globular proteins containing prosthetic group
➜ prosthetic group = non protein component
Fibrous proteins
➜ long insoluble molecules
➜ strong, tough and flexible
➜ not folded into 3D structures
➜ keratin - for protection
➜ elastin - to give elasticity (blood vessels?)
➜ collagen - for structure
Purines and Pyrimidines
PURINES:
➜ double ring with hexagon and pentagon
➜ large bases - A and G
➜ Ag silver is PUREine
PYRIMIDINES:
➜ smaller bases - T and C
➜ pyrimidine - 1 hexagon (y=cYtosine and thYmine)
DNA replication
➜ DNA helicase breaks hydrogen bonds and unwinds 2 strands of DNA
➜ Free nucleotides attracted to complementary bases
➜ DNA polymerase catalyses reaction between free floating nucleotides and original strand - phosphodiester bonds
➜ New strand of DNA formed
➜ Each new molecule of DNA formed is composed of one original strand and one newly formed molecule.
Degenerate code
➜ many amino acids can be coded for by more than one codon
DNA transcription
➜ RNA polymerase breaks hydrogen bonds and unwinds 2 strands of DNA
➜ 2 strands of DNA - sense (5’ to 3’) and antisense strand (3’ to 5’)
➜ antisense strand = template
➜ free RNA nucleotides pair with complementary bases -T replaced by U
➜ phosphodiester bonds formed between RNA nucleotides which is catalysed by RNA polymerase and double helix shape is reformed
➜ RNA polymerase reaches a stop signal
➜ mRNA detaches from DNA template and leaves nucleus
Splicing
➜ Introns removed and exons joined together
➜ only eukaryotes as prokaryotes do not have introns in DNA
➜ splicing forms mRNA from pre mRNA
DNA translation
➜ mRNA attaches itself between the 2 sub units of ribosome
➜ tRNA carrying an amino acid has an anticodon which is complementary to the FIRST codon of the mRNA
➜ second tRNA attaches to mRNA the same way as before (anticodon and codon)
➜ the 2 amino acids on the tRNA form a polypeptide bond and the first tRNA leaves, leaving behind amino acid
➜ process repeats to form polypeptide chain until stop signal
➜ protein moves away from ribosome
ATP - adenine triphosphate (contains ribose)
➜ small - moves in and out of cells
➜ water soluble - energy requiring process occurs in aqueous environments
➜ releases energy in small quantities - so energy isn’t wasted
➜ easily regenerated - can be recharged with energy
➜ ribose sugar pent sugar
➜ adenine group
➜ 3 phosphate groups
DNA nucleotide
The components of a DNA nucleotide are:
➜ a chain of nucleic acids
RNA nucleotide
The components of an RNA nucleotide are:
A ribose sugar with a hydroxyl (OH) group at the 2’ position
A phosphate group
One of four nitrogenous bases - adenine (A), cytosine(C), guanine(G) or uracil (U)
The presence of the 2’ hydroxyl group makes RNA more susceptible to hydrolysis
This is why DNA is the storage molecule and RNA is the transport molecule with a shorter molecular lifespan
Cation + function
calcium ions- nerve impulse transmission
muscle contraction
sodium ions- nerve impulse transmission
kidney function
potassium ions-nerve impulse transmission
stomatal opening
hydrogen ions- catalysis of reactions
pH determination
ammonium ions- production of nitrate ions by bacteria
Anion + function
nitrate ions- nitrogen supply to plants for amino acid and protein formation
hydrogen carbonate ions- maintenance of blood pH
chloride ions- balance positive charge of sodium and potassium ions in cells
phosphate ions- cell membrane formation, nucleic acid and ATP formation, bone formation
hydroxide ions- catalysis of reactions, pH determination
Triplet
➼ each amino acid is coded for by a sequence of 3 bases in a gene
mRNA
➼ made in nucleus
➼ 3 adjacent bases - codon
➼ carries the genetic code from the DNA in the nucleus to the cytoplasm, where it is used to make a protein during translation
tRNA
➼ found in cytoplasm
➼ amino acid binding site at one end and a sequence of 3 bases at the other end - anticodon
➼ carries the amino acids that are used to make proteins to the ribosomes during translation
rRNA
➼ forms the 2 subunits in a ribosome
➼ the ribosome moves along the mRNA strand during protein synthesis. The rRNA in the ribosome helps to catalyse the formation of peptide bonds between the amino acids
Genetic code
➼ sequence of codons in DNA or mRNA which codes for specific amino acids
➼ non-overlapping code
➼ degenerate -amino acids are coded for by more than 1 base triplet
➼ start and stop codon -> beginning and end of gene
➼ universal -> same specific base triplets code for the same amino acids in all living things
Purify DNA using a precipitation reaction
➼ break up the cells in your sample via pestle and mortar to break down cell wall
➼ make up a solution of detergent (detergent breaks down cell membrane), salt (helps DNA precipitate) and distilled water
➼ add the broken-up cells to a beaker containing the detergent solution.
➼ Incubate the beaker in a water bath at 60°C for 15 mins
➼ once incubated, put your beaker in an ice bath to cool the mixture down. When it’s cooled, filter the mixture. Transfer a sample of your mixture to a clean boiling tube.
➼ add protease enzymes to the filtered mixture to break down histones
dribble some cold ethanol down the side of the tube so it forms a layer on top of the DNA-detergent mixture
➼ the DNA will form a white precipitate
What are the implications of water having a high boiling point and being liquid at room temp?
-due to hydrogen bonds between water molecules.
It takes a lot of energy to increase the temperature of water and cause the water to evaporate
What do hydrogen bonds give water?
➼high specific heat capacity: energy needed to raise the temperature of 1 gram of a substance by 1 degrees celsius
-H bonds between water molecules can absorb a lot of energy
-water doesn’t experience rapid temp changes, which makes it a good habitat - stable temperature
➼ high latent heat of vaporisation:
(a lot of energy is used up when water evaporates)
-lots of energy to break the H bonds between water molecules
➼ water is good for cooling - why we sweat - when it evaporates, it cools the surface of the skin
What does water’s polarity make water?
➼ efficient transport medium: cohesive: attraction between molecules of the same type
-adhesion occurs between water molecules and other polar molecules and surfaces
-cohesion and adhesion results in capillary action - water rise up a narrow tube against gravity
➼ water acts as a solvent eg. for humans ions can dissolve in the water in blood and then be transported. Water acts as a medium for chemical reactions and also helps transport dissolved compounds in and out of cells
Why is ice less dense than water?
-water molecules are held further apart in ice than in liquid because water molecules form 4 H bonds to other water molecules, making a lattice shape - this makes ice less dense, which is why ice floats
Ice is less dense than water
-forms an insulating layer above the water below so water below doesn’t freeze-> aquatic creatures will therefore not freeze
Bonds
carbon - 4 bonds with other atoms
nitrogen- 3 bonds with other atoms
oxygen- 2 bonds with other atoms
hydrogen- 1 bond with another atom
Role of triglycerides
-energy storage
-thermal insulation to reduce heat loss
-buoyancy
-cushioning to protect vital organs
