Biological molecules Flashcards
what % of a cell is water?
80
explain what it means that water is a polar molecule
The share of the electrons between O and H is unequal, being closer to O, making O slightly negative and H slightly positive.
explain what hydrogen bonding is for water
The negative O atoms attract positive H atoms from other water molecules, connecting water molecules together, making water a very stable structure
what is specific heat capacity ?
the energy needed to raise the temp of 1 gram of a substance by 1 degrees Celsius
Why does water have a high specific heat capacity ?
The H-bonds between water molecules can absorb a lot of energy. This means it takes a lot of energy to heat it up. Doesn’t experience rapid temp changes, making it a good habitat.
Why does water have a high latent heat evaporation ?
It takes a lot of energy to break the H-bonds, therefore a lot of energy is needed til the water evaporates.
why is water having a high latent heat evaporation useful?
It is useful for organisms’ cooling systems, when mammals sweat, it cools the surface of the skin as energy is needed to break the H-bonds.
what makes water cohesive?
why is this useful ?
water is cohesive as it is a polar molecule
this helps water flow, which makes it great for transporting substances
also helps water to be transported up plant stems in transpiration stream
cohesive
water - water (same type)
adhesive
water - other (diff type)
water as a good solvent
the charges on the atoms in water causes it to be a good solvent and dissolve substances
why is ice less dense than water?
the water molecules are held further apart because each water molecule forms 4 H-bonds to other water molecules, making a lattice shape, which makes ice float
why is ice useful ?
forms an insulating layer on top of water, so the water doesn’t freeze, and organisms don’t freeze and can still move
uses for water as a solvent
dissolving ions into the water in blood for it to be transported, digestion, medium for metabolic reactions, transport
why is it useful that water is transparent ?
allows photosynthesis for aquatic life and vision
what is a carbohydrate ?
polymer of monosaccharides
what is a hexose monosaccaride?
examples??
a monosaccharide with 6 carbon atoms
e.g. - glucose / fructose / galactose
hexose sugars info :
- act as respiratory substrates
- simple and soluble so easily transported
- easily metabolised
how does glucose’s structure help its function ?
its structure makes it (highly) soluble, meaning it can be easlit transported
its bonds also contain lots of energy
what is ribose?
It is a pentose sugar (5 carbon atoms) that is the sugar component of RNA nucleotides
Role and solubility of fructose
main sugar in nectar / fruit
very soluble
Role and solubility of galactose
important role in production of glycolipids and glycoproteins
not very soluble
what is the bond called between monosaccharides ?
glycosidic bonds
what is a disaccharide ?
two monosaccharides joined together
what is a condensation reaction ?
a reaction that joins molecules together with the release of water molecules
what is a hydrolysis reaction?
a reaction that breaks larger molecules into smaller molecules using water molecules
what would you call any large molecule ?
a macro molecule
what is a dimer ?
a molecule composed of two single units (identical or similar)
what is an oligomer ?
a molecule composed of several single units (identical or similar)
what is a catabolic reaction ?
chemical reaction in an organism that breaks down molecules
what is an anabolic reaction ?
chemical reaction in an organism that builds larger molecules from smaller ones
what is maltose made up of ?
two alpha glucose molecules with an alpha 1-4 glycosidic bond
what is sucrose made up of ?
alpha glucose and fructose with an alpha 1-4 glycosidic bond
what is lacotse made up of ?
galactose and either alpha / beta glucose with an alpha / beta 1-4 glycosidic bond
what is the function of sucrose ?
provides energy for animals
translocated in phloem
what is the function of maltose ?
sugar produced from starch in germination
what is the function of lacotse ?
respiratory substrate in milk
what is amylose made up of ?
lots of alpha glucose molecules joined by alpha 1-4 glycosidic bonds
what is starch made up of ?
amylose and amylopectin
Describe amylose and how its structure helps its function
It is a long, unbranched chain of alpha glucose in a coiled structure, which makes it compact, so its really good for storage because you can fit more in a small space
Describe glycogen and how its structure helps its function
polysaccharide of alpha glucose, with lots of short side branches, meaning that the stored glucose can be released quickly
it is also very compact
Describe cellulose and how its structure helps its function
long, unbranched chains of beta glucose, held together by H-bonds to form microfibrils, which then bunch to form macrofibrils, giving it high mechanical strength
what happens when beta glucose molecules bond together ?
they form straight cellulose chains
which polysaccharides have a 1-6 glycosidic bond?
glycogen and amylopectin
which polysaccharides are soluble ?
none
which polysaccharides branch ?
glycogen (highly) and amylopectin
what are the chemical elements in lipids ?
carbon, hydrogen and oxygen
what is a triglyceride ?
a marcomoleucle, made up of a glycerol with 3 fatty acids attached to it by an ester bond
Describe esterification (synthesis of triglycerides)
- synthesised by the formation of an e bond between fatty acid and glycerol
- each e bond is formed by a condensation reaction
- triglycerides break down in a hydrolysis reaction
what is a saturated fatty acid ?
fatty acid that does not contain double bonds between the carbon atoms, meaning they can pack closer
general formula for a saturated fatty acid …
Cn H(2n+1) COOH
what is an unsaturated fatty acid ?
fatty acid with at least one carbon double bond, causing the chain to kink
what is a phosopholipid ?
macro molecule similar to triglycerides however replace one fatty acid with a (hydrophilic) phosphate group, that make up the phospholipid bilayer
why are triglycerides good for storage ? (hydrocarbon chain)
The long hydrocarbon fatty acid tails contain lots of chemical energy, so lots is released when they are broken down. Lipids contain x2 energy as carbohydrates because of this.
why are triglycerides good for storage ? (insoluble)
They are insoluble, so they don’t cause water to enter the cells which would make them swell. They bundle up as insoluble droplets because the fatty acid tails are hydrophobic, meaning they face inwards.
functions of triglycerides :
- major energy store / source
- protect organs
- waterproofing
- insulation
- buoyancy
- store carbon (bacteria)
why is the structure of a phospholipid suitable for cell membrane ?
The heads are hydrophilic, while the tails are hydrophobic, so they form a double layer, with the heads facing out both sides. The centre is hydrophobic, so water cannot pass through easily
describe the structure of cholesterol
Hydrocarbon ring structure attached to a hydrocarbon tail. The ring structure has a polar hydroxyl group attached to it
State the functions of cholesterol
- helps strengthen cell membrane
- needed to make vit D / hormones and bile
State how the structure of cholesterol helps its functions
- small size and flattened shape, allowing it to fit in between phospholipid molecules
- bind to the hydrophobic tails, causing them to pack closer, making the membrane less fluid and more rigid
Describe test for solid lipid
- crush food and place in test tube
- add ethanol and shake
- allow time to settle
- decant into another tube
- add equal vol of water (deionized)
- cloudy white suspension shows lipid presence
Describe test for liquid lipid
- add drops to test tube
- add equal vol of ethanol and water
- cloudy white suspension shows lipid is present
what are the factors that affect cholesterol :
genes / diet / gender / age
what is high cholesterol ?
when you have too much cholesterol in your body that it builds in the artery walls, increasing blood pressure and increasing chances of heart diseases
how to avoid high cholesterol
- balanced diet
- exercise regularly
- give up smoking
- take statins / aspirin which thin the blood
what are the effects of high cholesterol ?
causes atherosclerosis, which is the accumulation of cholesterol in artery walls, reducing blood flow, causing … high blood pressure / blood clots / heart attacks / stroke
why might cholesterol info be flawed ?
- subjects underestimate what they eat / lie / don’t record info precisely
- difficult to compare individuals (correlation is not causation)
what is the glucose colour range ?
blue / green / yellow / brown - orange / brick red
how do glucose strips work ?
they are embedded with a chemical that changes colour in the presence of a molecule
how could you test for diabetes ?
dip glucose strip in sample, if glucose is present, suggest diabetes (as glucose shouldn’t be in urine)
what is a qualitative test?
test which doesn’t provide range / numbers, instead provides a ‘present’ or ‘absent’, or even a description
state the elements present in carbohydrates
carbon, oxygen and hydrogen
what is a triose sugar and give an example
simple sugar containing 3 carbon atoms
Glyceraldehyde
what are furanoses and pyranoses ?
furanose - cyclic sugar containing 5 membered ring
pyranose - cyclic sugar containing 6 membered ring
define electronegativity
the measure of the ability of an atom to attract electrons
define dipole
a molecule that has both positive and negative charges
what are the monomers in a protein ?
amino acids
what is a dipeptide / polypeptide ?
two amino acids joined together / more than 2
how many polypeptides make up a protein ?
one or more
what is the general structure of an amino acid?
carboxyl group (COOH), amino acid group (NH2) and hydrogen atom attached to a carbon atom the difference is from the variable (R) group
what are the elements in a protein ?
carbon, oxygen, hydrogen, nitrogen and sometimes sulfur
what joins amino acids together ?
peptide bonds
what reaction joins amino acids together ?
condensation reaction (reverse is hydrolysis to break)
what is the primary structure ?
The sequence the amino acids are condensed together in a polypeptide chain. A change in just one amino acid may change the structure of the whole protein.
what is the secondary structure ?
When H-bonds begin to form between nearby NH+ and COO- groups, making alpha helices and beta pleated sheets. H-bonds are weak but collectively give strength
what is the tertiary structure ?
Chain of amino acid coils and folds further.
New R side chains able to interact with each other.
Held by 3 bonds: disulfide, ionic, H- bonds
This 3D structure that allows active site formation and gives functionality.
strength of - disulfide bonds
- ionic bonds
- H bonds
(proteins)
disulfide - fairly strong (double bond)
ionic - weaker (easily broken by pH change)
H-bonds - numerous and easily broken
what is the Quaternary structure ?
For proteins made up of several different polypeptide chains, the Quaternary structure is the way they are held together.
bonds in primary structure ..
peptide bonds
bonds in secondary structure ..
H-bonds
bonds in tertiary structure ..
ionic , disulfide, hydrophobic and hydrophilic interactions, H-bonds
Describe ionic bonds in proteins
Attractions between -ve R groups and +ve R groups on different parts of the molecule.
Easily broken by pH change
Describe disulfide bonds in proteins
Fairly strong (double) bond between sulfur in cysteine and another sulfur
Describe H bonds in proteins
Weak bonds between slightly +ve H atoms and slightly -ve other atoms in R groups
Describe hydrophobic/hydrophilic interactions in proteins
Hydrophobic R groups clump together, causing hydrophilic R groups to be pushed outside, affecting the way a protein folds
Describe a globular protein
Spherical, soluble proteins with a range of functions.
They are soluble due to hydrophilic R groups being pushed to the outside (caused by hydrophobic and hydrophilic interactions)
what will heating a protein do?
break the ionic / hydrophobic and hydrophilic interactions / H-bonds, which will change the 3D shape
Describe haemoglobin
- globular protein that carries oxygen round body in RBCs
- conjugated protein as non-protein group is attached, called a prosthetic group
- each of 4 polypeptide chains have a haem (prosthetic) group
- haem groups have iron, which oxygen binds to
Describe the globular protein insulin
- hormone secreted by pancreas
- helps regulate blood glucose level
- solubility is important as must travel in blood
- consists of two polypeptide chains, held by disulfide bonds
Describe amylase
- globular protein
- enzyme that catalyses the breakdown of starch
- made of a single chain of amino acids
- secondary structure consists of both alpha helices and beta pleated sheets
what are fibrous proteins ?
Tough, insoluble, rope - shaped proteins that are structural and fairly unreactive
Describe fibrous protein collagen
- found in animal connective tissues (bone/skin/muscle)
- very strong
- minerals can bind to increase rigidity (e.g. calcium for bones)
Describe fibrous protein keratin
- found in external structures like hair, skin, nails, feathers
- can be flexible or hard and tough
Describe fibrous protein elastin
- found in elastic connective tissues like walls of blood vessels / some ligaments
- elastic so allows tissues to stretch and return to original shape
what is the role of calcium ?
- transmission of nerve impulses
- release of insulin
- co factor for enzymes
- bone formation
what is the role of sodium ?
- generating never impulses
- muscle contraction
- regulating fluid balance
what is the role of potassium ?
- same 3 as sodium
- activates enzymes for photosynthesis
what is the role of hydrogen ?
- affects pH
- photosynthesis reactions in thylakoid membranes in chloroplast
what is the role of ammonium ?
- important source of nitrogen used to make amino acids (in plants)
what is the role of nitrate ?
- another source of nitrogen for plants
what is the role of hydrogencarbonate ?
- buffer which helps maintain pH of blood
what is the role of chloride ?
- ‘chloride shift’
- co factor for amylase
- some nerve impulses
what is the role of phosphate ?
- photosynthesis / respiration reactions
- synthesis of nucleotides / phospholipids and calcium phosphate
what is the role of hydroxide ?
- affects pH
test for reducing sugar :
- add Benedict’s (blue) and heat
- colour precipitate : blue / green / yellow / orange / brick red
what is a reducing sugar ?
monosaccharides (glucose) and some disaccharides (maltose / lactose)
test for non - reducing sugar :
- after reducing test, add HCl and heat to break down to monosaccharide
- neutralise with NaHCO3
- add Benedict’s
test for glucose …
- test strips with reagent that changes colour in presence
- compare to chart to determine concentration
test for starch ..
- add potassium iodide solution
- brown to blue - black
test for proteins ,,,
- add NaOH to make solution alkaline
- add copper (II) sulfate solution
- turn blue to purple
test for lipids …
- shake with ethanol
- pour into water
- white suspension will form
what is a biosensor ?
device that uses a biological molecule (enzyme) to detect a chemical
Rf value =
distance traveled by spot / distance by solvent
outline process of testing glucose conc
- set up diff concentrations of glucose
- do Benedicts test on each, then remove precipitate
- use colorimeter to measure absorbance of remaining solution
- make calibration curve
