2.1.2 - Biological Molecules Flashcards
What are the roles of water?
- solvent
- transport medium
- coolant
- habitat
What are the properties of water?
- floats as ice
- is polar and can form H-bonds (so can be a solvent and can undergo cohesion and adhesion)
- thermally stable
- metabolic
- liquid at room temp
- transparent
Why is the fact water floats as ice beneficial for organisms?
- provides a habitat (eg. for polar bears, penguins, etc)
- forms an insulating layer so animals in water below don’t freeze
Why is the fact water is polar and can form hydrogen bonds beneficial for organisms?
- polar substances can be dissolved in it
- useful for transport
- cohesion and tension allows water to move up the xylem in plants
- water’s cohesion gives water a surface tension, making it a habitat (eg. pond skaters)
Why is the fact water is thermally stable beneficial for organisms?
-provides a constant environment for organisms
Why is the fact water is metabolic beneficial for organisms?
-can be used in rxns like photosynthesis and hydrolysis rxns
Why is the fact water is a liquid at room temperature beneficial for organisms?
- can transport substances
- organisms can live in it
- less dense organisms can float
Why is the fact water is transparent beneficial for organisms?
-sunlight can reach organisms in shallow water so they can still photosynthesise
What is a polymer?
a molecule made up of many similar, smaller, repeating molecules (monomers) bonded together
What are monosaccharides?
the monomers that make up carbohydrates
What are the two types of glucose?
alpha glucose
beta glucose
What elements are all carbohydrates made up of?
carbon
hydrogen
oxygen
What are the 4 biological molecules?
water
carbohydrates
lipids
protein
What are the properties and structure of glucose?
- hexose monosaccharide (6 carbons)
- ring structure
- > makes it soluble so can easily be transported
What bonds join monosaccharides?
glycosidic bond
What are disaccharides?
two monosaccharides bonded together
What is a condensation reaction?
a reaction that joins smaller molecules together by forming a covalent bond(s) to form one larger molecule
water molecule is released
What is a hydrolysis reaction?
a reaction that uses a water molecule to break a covalent bond to form smaller molecules from a larger one
(opposite to condensation reaction)
What is a polysaaccharide?
a long chain of monosaccharides
Which two monosaccharides form maltose?
α-glucose and α-glucose
Which two monosaccharides form sucrose?
α-glucose and fructose
Which two monosaccharides form lactose?
α-glucose/β-glucose and galactose
Give three types of polysaccharide.
starch
cellulose
glycogen
What are the two types of starch?
amylose
amylopectin
What is the structure of amylose? (And how does that help it with its function?)
- long, unbranched chain of α-glucose
- coiled structure (compact - good for storage)
- insoluble in water (doesn’t cause water to enter cells via osmosis)
What is the structure of amylopectin? (And how does that help it with its function?)
- long, branched chain of α-glucose (side branches allow enzymes to get at the glycosidic bond easily so that glucose can be released easily)
- insoluble in water (doesn’t cause water to enter cells via osmosis)
How do plants store excess glucose?
as starch (when a plant needs more glucose for energy it breaks down the starch to release energy)
How do animals store excess glucose?
as glycogen
What is the structure of glycogen? (And how does that help it with its function?)
long, branched structure -similar to amylopectin but with more branches (useful for energy release)
What is cellulose?
the major component of cell walls in plants
What is the structure of cellulose?
- long, unbranched chains of beta-glucose
- straight, parallel cellulose chains
- cellulose chains are linked together by hydrogen bonds which form strong fibres called microfibrils (these provide structural support for the cells)
What are reducing sugars?
sugars that donate electrons or reduce another molecule
How do you test for reducing sugars?
- add Benedict’s solution (alkaline solution of copper II sulphate)
- heat in water bath
positive: brick red (precipitate)
negative: blue
How does the Benedict’s test work?
reducing sugars reduce the copper ions (give electrons to Cu2+)
How do you test for non-reducing sugars?
- boil with dilute hydrochloric acid
- neutralise with sodium hydrogen carbonate
- repeat Benedict’s test (add benedicts and heat in water bath)
How do you test for starch?
- add iodine
positive: blue/black
negative: yellow/brown
What are amino acids?
the monomers that make up proteins
What is a dipeptide?
two amino acids bonded together by a peptide bond
What is a polypeptide?
(a protein)
several amino acids bonded together
What elements are proteins made up of?
carbon hydrogen oxygen nitrogen sulphur
What bond joins amino acids?
peptide bond
What happens when two amino acids are joined?
amine group (H2N) joins to the carboxyl group (COOH)
water molecule is released
peptide bond is formed
occurs in a condensation reaction
What properties do globular proteins have?
- compact and roughly spherical
- have hydrophilic R-group on the outside of the molecule, making them water soluble
- have a tertiary structure
What are conjugated proteins?
globular proteins that contain a prosthetic group (a non-protein component)
Name some examples of globular proteins
haemoglobin
insulin
catalse
What is haemoglobin? And what properties does it have?
the red pigment in red blood cells which carries oxygen around the body
globular protein
-made from 4 polypeptide chains (2α and 2β subunits)
-each subunit has a haem prosthetic (iron) making a conjugated protein
What is insulin? And what properties does it have?
hormone involved in blood glucose concentration regulation
globular protein
-soluble (needs to be transported in blood)
-has 2 polypeptide chains held by disulfide bonds
What is catalase? And what properties does it have?
an enzyme that catalyses the breakdown of hydrogen peroxide (can be dangerous)
globular protein
-has 2 haem prosthetic groups
What properties do fibrous proteins have?
- strong, long molecules (not folded into complex shapes)
- contains lots of hydrophobic R-groups, making it insoluble
- flexible
Name some examples of fibrous proteins
collagen
keratin
elastin
What is collagen? And what properties does it have?
found in connective tissues (eg. skin, tendons, bone, etc)
- contains 3 polypeptide chains in a triple helix
- very strong and tightly packed (due to hydrogen bonds between chains in helix)
- hydrogen bonds can bond multiple collagens together
What is keratin? And what properties does it have?
present in hair, nails, skin, etc
- amount of disulfide bonds affect its structure:
- lots of disulfide bonds = hard and tough (eg. nails)
- not many disulfide bonds = flexible (eg. hair)
What is elastin? And what properties does it have?
found in elastic fibres (eg. blood vessels, alveoli in lungs, etc)
-has ability to stretch and expand and then go back to its normal shape
What elements are lipids made up of?
carbon
hydrogen
oxygen
What elements are nucleic acids made up of?
carbon hydrogen oxygen nitrogen phosphorus
How do you test for proteins?
-add biuret reagent (mixture of sodium hydroxide and copper sulphate)
positive: blue
negative: lilac
What are the levels of protein structure?
- primary
- secondary
- tertiary
- quaternary
What is the primary structure of a protein?
the sequence of amino acids
- involves peptide bonds
- directed by DNA
- influences how polypeptide folds
What bond(s) are involved in the primary structure of a protein?
peptide bonds
What is the secondary structure of a protein?
the folding of the amino acid chain
either:
-alpha helix (coiled)
-beta pleated sheet (folded)
What bond(s) are involved in the secondary structure of a protein?
hydrogen bonds
What is the tertiary structure of a protein?
the folding of the protein into its final shape
-involves hydrophilic/hydrophobic interactions, hydrogen bonds, ionic bonds and/or disulfide bridges
What bond(s) are involved in the tertiary structure of a protein?
- hydrophilic/hydrophobic interactions
- hydrogen bonds
- ionic bonds
- disulfide bridges
What is the quaternary structure of a protein?
when several polypeptide chains (units) are joined together
-doesn’t happen in all proteins
What bond(s) are involved in the quaternary structure of a protein?
- hydrophilic/hydrophobic interactions
- hydrogen bonds
- ionic bonds
- disulfide bridges
What are the uses of proteins?
- enzymes
- hormones
- antibodies
- transport (carrier/channel proteins in cell membranes)
- growth
- repair
What is the general structure of an amino acid?
- amine group (NH2)
- carboxy group (COOH)
- variable group
What are fatty acids made up of?
a carboxylate group and a hydrocarbon chain
What is a saturated fatty acid?
a fatty acid with no double bonds between carbon atoms
What is an unsaturated fatty acid?
a fatty acid with double bonds between carbon atoms
-C=C bonds cause a “kink” in the hydrocarbon chain, meaning the fatty acids can’t pack so closely together (hence, are often liquid at room temp)
What is a triglyceride made of?
three fatty acids bonded to one glycerol molecules
How is a triglyceride formed?
in an esterification (condensation) rxn
-OH of glycerol reacts with OH of fatty acid to form an ester bond and release a molecule of water
What is a phospholipid made up of?
two fatty acids and one phosphate group bonded to a glycerol molecule
What are the hydrophobic/hydrophilic properties of phospholipids?
- phosphate head is hydrophilic
- fatty acid tails are hydrophobic
- molecule is generally insoluble in water
- can form a bilayer
What are sterols?
lipids with a four carbon ring structure with a hydroxy group
- hydroxy group is polar and hydrophilic but the rest of the molecule is hydrophobic
eg. cholesterol
What is cholesterol?
a sterol made in the liver which is found in biological membranes to make the membranes more rigid/less fluid by binding to the hydrophobic tails of phospholipids so that they pack more closely together
How do you test for lipids?
via the emulsion test
- mix sample with ethanol (causes it to dissolve)
- then mix sample with water (causes it to precipitate
positive: cloudy
negative: clear
What ions are involved in biological processes?
Ca2+ Na+ K+ H+ NH4 + NO3 - HCO3 - Cl- PO4 3- OH-
How can biological molecules be separated?
by paper or thin layer chromatography
Rf =
distance moved by solute
_____________________
distance moved by solvent
How can the concentration of a substance in a solution be measured quantitatively?
- using a colorimeter
- using a biosensor
What are calcium ions used for in living organisms?
- nerve impulse transmission
- muscle contraction
What are sodium ions used for in living organisms?
- nerve impulse transmission
- kidney function
What are potassium ions used for in living organisms?
- nerve impulse transmission
- stomatal opening
What are hydrogen ions used for in living organisms?
- catalysing reactions
- determining pH
What are ammonium ions used for in living organisms?
-producing nitrate ions (by bacteria)
What are nitrate ions used for in living organisms?
- supplying nitrogen to plants
- amino acid and protein formation
What are chloride ions used for in living organisms?
-balancing charge of Na+ and K+ ions in cells
What are phosphate ions used for in living organisms?
- cell membrane formation
- nucleic acid and ATP formation
- bone formation
What are hydroxide ions used for in living organisms?
- catalysing reactions
- determining pH
