Module 2.2 - Biological Molecules Flashcards
What is a condensation reaction?
- 2 molecules joined together
- water is removed
- two OH groups react
- covalent bonds break and form
What is a hydrolysis reaction?
- two molecules split apart
- water is added
What is a monomer?
Small molecule which binds to other identical molecules to form a polymer
What is a dimer?
2 monomers joined together
What is a polymer?
Lots of monomers joined together
What’s the monomer and polymer of a carbohydrate? ( C, H, O)
- monosaccharides ( e.g glucose )
- polysaccharides ( e.g starch )
What’s the monomer and polymer of a protein? ( C, H, O, N, S)
- amino acids
- polypeptides, proteins
What’s the monomer and polymer of nucleic acid? ( C, H, O, N, P)
- nucleotides
- DNA, RNA
What is a hydrogen bond?
Weak interaction between a slightly negative charge on one atom and a slightly positive hydrogen atom
Explain water as a liquid and what this allows
-molecules move and continually make and break hydrogen bonds
-hydrogen bonds make it harder for water to evaporate
-flows easily ( low viscosity) even though it has hydrogen bonds
Can:
-provide habitats for loving things in rivers, lakes,and seas
-form a major component of tissues in organisms
-provide a reaction medium for chemical reactions
-provide an effective transport medium ( e,g in blood or vascular tissue (
Explain the density of water
- provides ideal habitat so aquatic organisms can float
- becomes more dense as it cools until 4*c. As it freezes, ice becomes less dense than liquid water due to hydrogen bonds and the structure that forms
Why is ice being less dense than water beneficial?
- aquatic organisms have a stable environment for winter
- ponds and other bodies of water are insulated against extreme cold, the ice reduced the rate of heat loss from the pond
Explain water as a solvent and how this is beneficial
- good solvent inc for ionic solutes ( NaCl) and covalent solute (glucose)
-polar so attracts negative and positive parts of the solute
-water molecules cluster around charges parts or molecules or ions to separate and dissolve them forming a solution
Benefits of this|
-molecules can move around and react in water, e.g cytoplasm
-molecules and ions can be transported around organisms whilst dissolved
Explain the cohesion and surface tension of water and why this is beneficial
- hydrogen bonds cause cohesion
- at surface of water, cohesion of water molecules at surface to ones below, stronger than attraction to air above, this means surface contracts ( molecules pulled inwards ) so water can resist force applied to it= surface tension
- columns of water in plant vascular tissue pulled up xylem together from roots
- insects can walk on water ( e.g pond skaters)
Explain the high specific heat capacity of water and how this is beneficial
- H bonds hold water molecules close together, requires lots of energy to increase KE and temperature.
- (4.2) doesn’t heat or cool easily
- living things need stable temperature for enzyme controlled reactions to happen
- aquatic organisms need a stable environment to live in
Explain the high latent heat of evaporation of water and why this is beneficial?
- helps molecules break away from each other to become a gas, due to H bonds, evaporation requires lots of energy
- water can help cool things down when it evaporated due to this, e.g mammal swear and plant cooling
Explain water as a reactant and why this is beneficial?
- e.g photosynthesis and hydrolysis ( digestion of starch proteins and lipids
- important for digestion and syntheses
(MA) What is the structure of a protein?
- primary structure: the specific order that amino acids are joined together in a polypeptide chain. Joined with peptide bonds
- secondary structure: the coiling/folding of the polypeptide chain into alpha helixes or beta pleated sheets. Held together with H bonds
- tertiary structure: the overall 3D shape of the protein. Held together with H bonds, ionic bonds (between oppositely charged R groups), disulphide bridges (between sulphurs on different amino acids) and hydrophobic and hydrophilic interactions (hydrophobic R groups move towards the inside of the molecule whilst the hydrophilic R groups move towards the outside)
- quaternary structure: where more than one polypeptide chain are held together to make a final functional version of the protein
(MA) How does DNA structure determine the specific shape of proteins?
- DNA codes for proteins
- DNA is transcribed + then translated into a polypeptide chain
- 3 bases code for one amino acid
- sequence of bases determines the sequence of amino acids, the primary structure
- secondary structure: the coiling/folding of the polypeptide chain into alpha helixes/beta pleated sheets. Held together with H bonds
- tertiary structure: overall 3D shape of the protein
- quaternary structure: where more than one polypeptide chain are held together to make the final functional version of the protein
(MA) What are the properties of collagen for its functions?
- high tensile strength
- not elastic
- flexible
- insoluble
(MA) What are the roles of fats in organisms?
- energy source
- energy store: lipids stored in adipose cells
- phospholipid bilayers
- thermal insulation
- myelin sheath of neurones: electrical insulation
- steroid hormones
- waxy cuticle of leaves: prevents drying out
(MA) What are the similarities between collagen and haemoglobin?
- both proteins made of amino acids
- held together with peptide bonds
- both tertiary structures held together with H bonds, ionic bonds + disulphide bonds
- both have quaternary structures + so contain more than one polypeptide chain
(MA) What are the differences between collagen and haemoglobin?
- haemoglobin is globular, collagen is fibrous
- Hb has hydrophobic R group on inside + hydrophilic R group on outside, collagen doesn’t
- Hb has 4 polypeptide chains, collagen has 3
- Hb has 2 different types of polypeptide chain, collagen’s are all the same
- Hb contains a wider range of amino acids, 1/3rd of collagen’s amino acids are glycine
(MA) Compare the structures of glycogen and collagen.
- glycogen is a polysaccharide (carbohydrate), collagen is a protein
- monomers in glycogen are alpha glucose units, they are amino acids in collagen
- all the monomers in glycogen are identical, there are different amino acids in collagen
- the monomers are joined with glycosidic bonds in glycogen but with peptide bonds in collagen
- glycogen is branched, collagen is unbranchced
- glycogen is non-helical, collagen is helical
- there is only one chain per molecule in glycogen, there are three chains per molecule in collagen
- there are no cross links in glycogen molecules, there are cross links between chains in a collagen molecule
(MA) Compare the structures of glycogen and cellulose.
- there’s no H bonding in glycogen, there is between chains in cellulose
- glycogen is a polysaccharide of alpha glucose, cellulose is a polysaccharide of beta glucose
- glucose molecules are joined with both 1,4 and 1,6 glycosidic bonds in glycogen but only 1,4-glycosidic bonds in cellulose
- glycogen is branched, cellulose isn’t
- glycogen has no fibres but cellulose does
- all the glucose monomers are in the same orientation in glycogen but alternate glucose molecules are in orientations in cellulose
(MA) Compare the structures of phospholipids and triglycerides.
- 2 fatty acids in phospholipids but 3 in triglycerides
- 2 ester bonds in phospholipids but 3 in triglycerides
- phosphate group in phospholipids but none in triglycerides
- both contain glycerol
- both contain fatty acids
- both contain ester bonds
- both contain C, H and O
(MA) Why is glycogen a good storage molecule?
- insoluble
- so doesn’t reduce water potential of cells
- can be hydrolysed easily
- as there are lots of branches for enzymes to attach to
- compact
- therefore high energy content for mass
(MA) What are the key points about water (properties/uses)?
- hydrogen bonding between the molecules
- temperature stability
- ice floats
- solvent
- transport medium
- transparent
- use in transpiration, photosynthesis + hydrolysis (plants)
- cooling
- surface
(MA) Explain water’s temperature stability and the benefits of this.
- many/stable hydrogen bonds between molecules
- lots of energy needed to break H bonds to force apart molecules
- high specific heat capacity
- large amount of energy must be removed for water to freeze
- liquid at normal temperatures
- water slow to change temperature: temperature remains fairly constant
- lakes/oceans/large volumes, provide thermally stable environment
- internal body temperature changes minimised for aquatic life
(MA) Explain why ice floats and the benefits of this.
- water expands as it freezes/ice is less dense than water
- ice less dense because molecules spread out
- allows mx. no. of H bonds to form, molecules form lattice
- ice floats on water
- insulates water beneath
- large bodies of water don’t freeze completely
- organisms don’t freeze/animals can still swim
- causes currents to circulate nutrients
- support for large organisms on ice (penguins/polar bears)
(MA) Explain why water can be used as a solvent and the benefits of this.
- solvent for polar/ionic substances, ions attracted to water
- solubility of gases in environment
- allows reactions to take place
- water plants can obtain nutrients e.g. nitrates for amino acids/proteins
(MA) Explain why water can be used as a transport medium.
- transport medium for food particles for some water dwelling organisms
- transport for male gametes for external fertilisation, stops them drying out
- transport medium for blood cells
- low viscosity, aids movement
(MA) Explain the benefits of water’s transparency.
- water is transparent to light
- plants can photosynthesis under water
(MA) Explain the uses of water in plants.
- can form long unbroken columns of water
- in the xylem in transpiration
- due to cohesion
- is a reactant in photosynthesis
- plays a key role in hydrolysis reactions (in all living organisms)
(MA) Explain why water can be used for cooling and the benefits of this.
- used for cooling because evaporation of water has a cooling effect
- e.g. sweating/panting/transpiration
(MA) Explain why water can be used as a surface.
- organisms can use the surface of the water (as a habitat)
- due to high surface tension
- e.g. water boatmen/lily pads
(MA) Describe the test for proteins.
- add biuret solution
- positive result: blue to lilac
- 4 nitrogen atoms from 2 dipeptides react with copper (II) ions to give lilac colour
(MA) Describe the test for non reducing sugars.
- boil with dilute HCl to hydrolyse sugar into a reducing sugar (then neutralise the acid with NaHCO3) then add Benedicts reagent and heat
- positive result: blue to red precipitate (yellow/green/orange)
(MA) Describe the test for starch.
- add iodine
- positive result: orange to blue/black
- iodine reacts + forms a complex in helix of amylose in starch
(MA) Describe the test for lipids.
- add alcohol then mix with water
- positive result: white emulsion
- lipids are insoluble in water but soluble in alcohol. Ethanol will emulsify lipids into many tiny droplets which form the cloudy white layer
(MA) How do you find the concentration of sugar of an unknown solution?
- get known concentrations of reducing sugar
- heat with an excess of Benedicts
- use the same volumes of solutions each time
- they will have a colour change to red
- remove the precipitate to obtain filtrate
- calibrate colorimeter
- using water
- read the transmission/absorbance for each known concentration’s filtrate
- more transmission/less absorbance of filtrate = more sugar present
- draw a calibration curve
- plotting transmission/absorbance against sugar concentration
- use reading of transmission/absorbance of unknown sugar and read off graph to find concentration
(MA) Describe the structure and uses of amylose.
- carbohydrate, polysaccharide
- alpha glucose joined with 1,4-glycosidic bonds. coiled, unbranched + compact
- energy storage in plants
- insoluble
- part of starch stored in starch grains with iodine + turns it black
(MA) Describe the structure and uses of amylopectin.
- carbohydrate, polysaccharide
- alpha glucose joined with 1,4-glycosidic bonds. branches form with 1,6-glycosidic bonds. compact
- energy storage in plants
- insoluble
- part of starch stored in starch grains, branches hydrolysed to release alpha glucose for use in respiration for energy, less branched than glycogen
(MA) Describe the structure and uses of glycogen.
- carbohydrate, polysaccharide
- alpha glucose joined with 1,4-glycosidic bonds. lots of branches form with 1,6-glycosidic bonds, more compact than starch
- energy storage in animals
- insoluble
- branches hydrolysed to release alpha glucose for use in respiration for energy, more branched than glycogen, more ends for hydrolysis, more energy release
(MA) Describe the structure and uses of cellulose.
- carbohydrate, polysaccharide
- cellulose chain: beta glucose joined with 1,4-glycosidic bonds, every other beta is flipped 180 degrees in relation to the last, long, unbranched
- microfibrils are formed when chains cross link with H bonds (which cross link to form macrofibrils)
- structural in plants, cell walls
- insoluble
- very strong, pectin glues many cellulose macrofibrils together for cell walls in a criss cross structure for increased strength, this lets water through but prevents the wall from bursting
(MA) Describe the structure and uses of haemoglobin.
- globular protein
- quaternary structure with 4 subunits, 2 alpha and 2 beta chains. Each chain has a haem prosthetic group
- carry oxygen in the blood
- soluble
- haem group is a non protein part, containing an Fe2+ ion which binds to the oxygen
(MA) Describe the structure and uses of collagen.
- fibrous protein
- collagen chain: every 3rd amino acid is glycine
- collagen molecule: quaternary structure made of 3 chains tightly wound around each other, H bonds between them gives the molecule strength
- collagen fibrils: collagen molecules cross linkes w covalent bonds
- structural in animals, arterial walls, cartilage, tendons, connective tissue
- insoluble
- high tensile strength, not elastic, flexible
(MA) Describe the structure and uses of triglycerides.
- lipid
- 3 fatty acids joined to a glycerol molecule w ester bonds
- energy storage in animals
- insoluble
- compact storage in adipose cells, can be broken down more completely than carbs, releases more energy and metabolic water
(MA) Describe the structure and uses of phospholipids.
- lipid
- 2 fatty acid tails (bonded w ester bonds) + a phosphate group head bonded to a glycerol molecule
- phospholipid membranes, bilayers
- soluble head, insoluble tails
- more unsaturated (double bonds) in fatty acid tails the more fluid a membrane, useful to prevent freezing in colder climates (non homeotherms)
(MA) Describe the structure and uses of cholesterol.
- lipid
- made from 4 carbon rings
- steroid hormones, decrease fluidity in membranes
- insoluble
- can be deposited in blood vessels causing atherosclerosis, leading to narrowed vessels + increased blood pressure as well as risk of myocardial infarction
How many covalent bonds can carbon form?
4
Are lipids polymers?
No, while they’re made of smaller molecules they’re different from one another
What is the monomer of carbohydrates?
Monosaccharides
What is the polymer of carbohydrates?
Polysaccharides
What is the monomer of proteins?
Amino acids
What is the polymer of proteins?
Polypeptides
What is the monomer of nucleic acid?
Nucleotides
What is the polymer of nucleic acid?
DNA + RNA
Describe condensation reactions.
- links biological molecules together
- water molecule is released
- covalent bond is formed
- larger molecule is formed
Describe hydrolysis reactions.
- splits biological molecules apart
- water molecule is used
- covalent bond is broken
- smaller molecules are formed
What elements make up a carbohydrate and in what ratio?
- carbon, hydrogen and oxygen
- Cn(H2O)n
What is the name of 3 carbon monosaccharides?
Triose sugars
What is the name of 5 carbon monosaccharides?
Pentose sugars
What is the name of 6 carbon monosaccharides?
Hexose sugars, most common (e.g. glucose)
Describe the bonding between monosaccharides.
- joined by a covalent bond called a glycosidic bond
- 2 monosaccharides join w a glycosidic bond in a condensation reaction to form a disaccharide
- hydrolysis reactions w water can break the glycosidic bond
- polymers are built + broken in the same way
What is the difference between alpha glucose and beta glucose?
- alpha: OH group is below the plane of the ring
- beta: OH group is above the plane of the ring
How is energy released from glucose?
- aerobic respiration
- glucose+oxygen–>carbon dioxide+water
- C6H12O6+O2–>6CO2+6H2O
- respiration: set of metabolic reactions + processed controlled by enzymes. Bonds in glucose broken making CO2 + H2O molecules, releasing energy which is used to make ATP
- enzymes specific due to active site’s shape
- plants + animals can only break down alpha glucose due to the difference in structure. Beta glucose can’t be respire so can’t be used for energy storage
What is the result of the condensation reaction of 2 alpha glucose?
Maltose (a disaccharide)
Lots form the polysaccharide amylose
Reaction controlled by enzymes
What type of bond holds alpha glucose together in amylose?
1,4-glycosidic bond
Describe the shape of amylose and why.
- helical shape due to shape of the glucose + glycosidic bond
- held in place by H bonds
- unbranched and compact
- insoluble
Is amylose soluble?
No
What causes the colour change when iodine solution is added to amylose?
Iodine can get caught in spring shape of amylose making it go from orange to blue/black
Why does iodine change to blue/black when in the presence of starch?
Reacts with the amylose in starch
What two molecules is starch made up of?
Amylose and amylopectin
What is amylopectin?
A branch of alpha glucose chains with 1,4-glycosidic bonds joined at ends to another chain by a 1,6-glycosidic bonds
What’s the use of starch in plants?
- starch stored in starch grains, chloroplasts + storage organs (in grains) e.g. potatoes
- it’s a store of energy as can be hydrolysed (hydrolysis) into alpha glucose (for respiration) molecules by enzymes
What is the structure of glycogen and what are its uses?
- polysaccharide of alpha glucose, broken down using enzymes (hydrolysis) to release glucose for respiration
- 1,4 linked chains are shorter + more branched (1,6) than starch
- more branches=more ends to be broken off=faster break down=faster energy release
- more compact that starch so can store more energy in less space
- found in glycogen granules in animal cells e.g. liver + muscle
What are the similarities between starch and glycogen?
- insoluble in water + so doesn’t decrease water potential of cells
- store glucose molecules in chains so they can be easily broken off + glucose can be used in respiration
Why is it important that glycogen is more branched than amylopectin?
- more branches so more ends that can be broken off in animals
- faster break down into glucose molecules through hydrolysis reactions so energy is released faster
Why are glycogen and starched called storage molecules whereas alpha glucose is termed as an energy source?
Starch and glycogen are polysaccharides so too big for immediate use but alpha glucose is monosaccharide so can have immediate use
What is the monomer used to make up cellulose?
Beta glucose
Describe the structure of cellulose.
- beta glucose form 1,4-glycosidic bonds in a long, straight + unbranched hydrocarbon chain
- every beta glucose flipped 180° from last to form the glycosidic bond
- cellulose chains arranged in a particular way to make cell walls
- H bonds form between OH groups on neighbouring chains
- cellulose chains become cross linked to form a microfibril
- microfibrils held together by H bonds to form macrofibrils
Describe the structure of macrofibrils.
- embedded in pectin (polysaccharide) gluing them together into a criss cross structure (held in place by H bonds) form cell walls
- criss cross structure allows H2O to pass through easily but as macrofibrils are v strong water moving into plant cells doesn’t cause them to burst. Wall presents bursting + in turgid cells help support whole plant
What is similar between glucose and fructose?
Same elements C, H, O
What is a difference between glucose and fructose?
Glucose: hexose
Fructose: pentose
Give an example of how to arrangement of microfibrils and macrofibrils can be beneficial in plants.
- control cell shape
- macrofibrils arrangement in guard cells cause opening + closing of stomata
What examples, other than cellulose, of polymers that provide support in organisms?
- peptidoglycan (murien) bacterial cell walls
- chitin, exoskeleton of insect
Where is starch found?
Plants
What is starch a polysaccharide of?
Alpha glucose
What are the characteristics of starch?
- mixture of amylose + amylopectin molecules
- stored in starch grains, chloroplasts + storage organs
- store of energy as it can be broken down to alpha glucose by enzymes by hydrolysis
- mixture of unbranched, coiled amylose + branched amylopectin
- insoluble (doesn’t affect water potential of cells)
What is the role of starch?
Energy storage
Where is glycogen found?
Animals (liver + muscle cells)
What is glycogen a polysaccharide of?
Alpha glucose
What are characteristics of glycogen?
- more branched, easier to break down
- insoluble
- form granules
- 1,4 and 1,6
What is the use of glycogen in animals?
Energy storage
Where is cellulose found?
Plants (cell walls)
What is cellulose a polysaccharide of?
Beta glucose
What are the characteristics of cellulose?
- insoluble
- v strong
- unbranched
What is the use of cellulose?
Structural (cell walls)
Explain why glycogen is referred to as an energy storage.
polysaccharide of alpha glucose that can’t be repaired directly, needs to be hydrolysed into glucose to be respired. It’s branched to allow maximum hydrolysis
What kind of reaction breaks down polysaccharides?
Hydrolysis
Name the bond in which a pair of electrons is shared between atoms.
Covalent
Name the small unit which is joined many times to form a polymer
Monomer
Where might you expect to see hydrogen bonds forming in a polysaccharide?
Between polysaccharide chains
Describe the structure of a cellulose microfibril.
- made of several hundred beta glucose chains
- every other flipped 180°
- hydrogen bonds between chains
What is a hexose sugar?
6 carbon sugar
What kind of bonds holds a polysaccharide together?
Glycosidic
What is the formula of a pentode sugar?
C5H10O5
Alpha and beta glucose have different shapes but the same formula, what is the word to describe this?
Isomer
What happens in the condensation reaction of a polysaccharide?
- water formed
- chains bonded together via an oxygen atom through a covalent bond
Describe the structure of amylopectin.
Branching of alpha glucose chains with 1,6-glycosidic bonds joined at the ends
Describe the structure of amylose.
Thousands of alpha glucose in 1,4-glycosidic bond
What is the function of proteins?
- structural: muscle, bone
- carrier + channel proteins
- enzymes
- many hormones
- antibodies
- crucial for growth, repair + metabolic activity
- they’re the polymers of amino acids
What is the structure of an amino acid?
- amino group (amine): NH2
- acid group: COOH
- R group: hydrocarbon (may contain impurities)
What effect can the R group have on the properties of the amino acid?
- small/large
- hydrophilic/hydrophobic
- opposite charges
How do plants make proteins?
Make their own from nitrates in the soil to form amino acids to form proteins
How do animals form proteins?
- need protein in their diet
- broken up into amino acids in digestion + built back up to make proteins for the body
What is transcription?
Taking the message from the original DNA code + making a copy into messenger RNA (mRNA)
Describe the process of transcription.
- DNA helicase enzyme unwinds the double helix of DNA
- 2 strands of DNA are separated so free nucleotides can fit in
- free nucleotide bases attach to the DNA by their complementary base pair rules
- the single mRNA strand moves away from the DNA helix + another enzyme zips the 2 strands of DNA back together
- the single mRNA strand is small enough to leave the nucleus + enter cytoplasm
What is translation?
Taking the message from RNA + translating it into a chain of amino acids to make a protein
Describe the process of translation.
- the mRNA enters the ribosome
- tRNA (transfer RNA) enters the ribosome + brings a specific amino acid w it that corresponds to the codon on the mRNA strand
- the tRNA has an anticodon matching the mRNA codon so they pair together using complementary base pair rules
- the amino acid brought by the first tRNA is attached to the second amino acid by a peptide bond
- when all the code has been read + amino acids joined together the mRNA leaves the ribosome + a new protein has been made
How many possibilities are there for proteins from 4 amino acids?
20^4=160000
What enzymes are used to break down proteins and how do they do this?
- protease enzymes
- break the peptide bond
- used in digestion + breakdown of hormones so their effect isn’t constant
Give one example of something that happens to the body from not being able to rebuild proteins.
aging, skin loses elasticity as can’t rebuild collagen that makes skin smooth + elastic
What is elastin used for and where is it found?
- cross linking + coiling for strength
- skin, lungs, bladder, blood vessels
What is a conjugated protein and what is an example of one?
one with a prosthetic (non amino acid) group e.g. haemoglobin
What is pepsin and what is its structure?
- protease enzyme, digestive
- single polypeptide chain, 327 amino acids, symmetrical tertiary structure, mainly acidic R groups (stable)
What is the structure of insulin?
- 2 polypeptide chains, a chain begins with alpha helices, chain ends with beta
- chains fold into tertiary structure held together by disulphide links
How do polypeptide chains avoid tangling or breaking?
- stabilised by becoming coiled (alpha helix) or pleated (beta pleated sheet)
- held in place by H bonds
- coiling/pleating is the secondary structure of the protein
- combined strength of lots of H bonds gives stability
How is the secondary structure dependent on the primary structure?
- primary structure is the unique sequence of amino acids in the protein
- different proteins have different combinations of amino acids which each have different R groups with different properties
- these different properties mean H bonds form in different places in the pleat/coil meaning some are more/less pleated/coiled than others
What is the tertiary structure of a protein?
- overall 3D structure of a protein
- coil/pleat coils/folds into final shape (this folding is dependent on primary structure)
- tertiary structure is key to protein’s function (e.g. hormone needs to fit into complementary receptor/enzyme’s active site)
Describe each type of bond maintaining the tertiary structure.
- disulphide bond: cysteine (amino acid) contains sulphur. Where 2 cysteines found close together a covalent bond can form
- ionic bond: R groups sometimes carry charge. Oppositely charged amino acids near each other from ionic bonds
- H bonds: slightly +vely charged groups close to slightly -ve forms a H bond
- hydrophobic + hydrophilic interactions: in water based environment, hydrophobic amino acids most stable if held with water excluded. Hydrophilic amino acids tend to be found on outside of globular proteins with hydrophobic in the centre
What are the bonds in the primary structure of a protein?
covalent polypeptide bond
What are the bonds in the secondary structure of a protein?
weak hydrogen bond
What are the bonds in the tertiary structure of a protein?
- ionic bonds
- H bonds
- hydrophobic/hydrophilic interactions
- disulphide bonds
What are the 2 protein shapes?
- globular
- fibrous
Describe the properties of globular proteins.
- balls (circular)
- soluble, hydrophobic groups found in centre of ball + hydrophilic on inside
- role: metabolic
- e.g. enzymes, plasma proteins, antibodies, Hb
Describe the properties of fibrous proteins.
- fibred
- insoluble
- role: structural
- e.g. collagen, keratin
Explain how the denaturation of a protein occurs.
-heat energy gives molecules KE making them vibrate + can break bonds
-heating proteins can break bonds holding tertiary structure in place, changing shape of protein so it denatures
-shape of a protein is vital to its function so once bonds broken + tertiary structure lost protein won’t function properly
(-covalent bonds are v strong so need more heat energy to break them)
Explain, in terms of enzymes, why the body must maintain an internal temperature of 37⁰C.
- optimum temperature, lower it won’t work as efficiently
- heat energy gives molecules KE so vibrate + can break bonds
- heating proteins can break bonds holding tertiary structure in place, changing shape of protein (denatures) as protein loses shape of active site
What are the inorganic cations involved in biological processes?
- calcium, Ca2+
- sodium, Na+
- potassium, K+
- hydrogen, H+
- ammonium, NH4 +
What are the inorganic anions involved in biological processes?
- nitrate, NO3 -
- hydrogencarbonate, HCO3 -
- chloride, Cl-
- phosphate, PO4 3-
- hydroxide, OH-
How are calcium ions, Ca2+, used in biological processes?
- increase rigidity of bone, teeth + cartilage + is a component of crustacean’s exoskeleton
- important in blood clotting + muscle contraction
- activator for several enzymes e.g. lipase, ATPase, cholinesterase
- stimulates muscle contraction + regulates transmission of nerve impulses
- regulates permeability of cell membranes
- importance for cell wall development in plant + formation of middle lamella between cell walls
How are sodium ions, Na+, used in biological processes?
- Involved in regulation of oncotic pressure, control of water levels in body fluid + maintenance of pH
- Affects absorption of carbohydrate in the intestine + water in the kidney
- Contributes to nervous transmission + muscle contraction
- Constituent of vacuole in plants which helps maintain turgidity
How are potassium ions, K+, used in biological processes?
- Involved in control of water levels in body fluid + maintenance of pH
- Assists active transport of materials across the cell membrane
- Involved in synthesis of glycogen + protein + breakdown of glucose
- Generates healthy leaves + flowers in flowering plants
- Contributes to nervous transmission + muscle contraction
- Component in vacuoles in plants, helping maintain turgidity
How are hydrogen ions, H+, used in biological processes?
- Involved in photosynthesis + respiration
- Involved in transport of O2 + CO2 in the blood
- Involved in regulation of blood pH
How are ammonium ions, NH4+, used in biological processes?
- A component of amino acids, proteins, vitamins + chlorophyll
- Some hormones are made of proteins e.g. insulin
- An essential component of nucleic acids
- Involved in maintenance of pH in the human body
- A component of the nitrogen cycle
How are nitrate ions, NO3-, used in biological processes?
- A component of amino acids, proteins, vitamins + chlorophyll
- An essential component of nucleic acids
- Some hormones are made of proteins, which contain nitrogen e.g. insulin
- A component of the nitrogen cycle
How are hydrogencarbonate ions, HCO3-, used in biological processes?
- Involved in regulation of blood pH
- Involved in transport of CO2 into + out of the blood
How are chloride ions, Cl-, used in biological processes?
- Helps production of urine in the kidney + maintaining water balance
- Involved in transport of CO2 in + out of the blood
- Regulates Hb’s affinity for O2 rough allosteric effects on Hb molecule
- Involved in regulation of blood pH
- Used to produce HCl in the stomach
How are phosphate ions, PO4 3-, used in biological processes?
- Increases rigidity of bone, teeth + cartilage + is a component of exoskeleton of crustaceans
- Component of phospholipids, ATP, nucleus acids + several important enzymes
- Involved in regulation of blood pH
- Helps root growth in plants
How are hydroxide ions, OH-, used in biological processes?
-Involved in regulation of blood pH
Describe the structure of haemoglobin.
-has more than one polypeptide subunit joined to make the final protein (quaternary structure)
-has a quaternary structure with 4 subunits: 2 alpha + 2 beta, each with a prosthetic haem group (conjugated protein)
-4 subunits = 4 haem groups = 4 oxygen molecules per haemoglobin
primary structure: range of amino acids (specific order)
secondary structure: mostly alpha helices
tertiary structure: alpha chains + beta chains
quaternary structure: 2 alpha + 2 beta chains
Describe the structure of collagen.
- fibrous
- collagen molecules’ quaternary structure made up of 3 polypeptide chains tightly wound around each other, H bonds between them gives molecules strength
- every 3rd amino acid on each polypeptide chain is glycine, small allowing close packing
- covalent bonds cross link parallel to collagen molecules, forming collagen fibril
- ends of molecules are staggered to add strength
- many fibrils form a collagen fibre
What is the function of collagen?
- structural
- lines arterial walls, prevents blood at high pressure bursting walls
- tendons, small muscle to pull bone for movement
- bones, collagen reinforces w other materials to make them hard
- cartilage + connective tissue
- cosmetic treatments: collagen injections can make lips look fuller
What are the properties of collagen?
- high tensile strength
- not elastic
- flexible
- insoluble
Compare collagen and haemoglobin in terms of the type of protein they are, their solubility, their prosthetic group and their roles.
- collagen: fibrous, insoluble, no prosthetic group, structural
- Hb: globular, soluble, prosthetic haem group, transport O2 around the body
What are some of the differences in structure between glycogen and collagen?
- g: made up of glucose, c: made up of amino acids
- g: carbohydrate, c: protein
- g: CHO, c: CHON
- g: non helical, c: helical
- g: branched, c: unbranched
- g: glycosidic bonds, c: peptide bonds
What are lipids soluble in?
organic solvents like alcohol but NOT water
What is a solid lipid called?
a fat
What is a liquid lipid called?
an oil
What are the role of lipids in organisms?
- energy storage; lipids stored in adipose cells
- energy source
- phospholipid bilayers
- thermal insulation
- myelin sheath of neurones; electrical insulation
- steroid hormones
- waxy cuticle outside leaves; prevents drying out
Which 2 major groups of lipids are glycerol and fatty acid found?
glycerolipids (energy store/source) and glycerophospholipids (phospholipids)
What is the molecular/structural formula of glycerol?
C3H8O
CH2OHCHOHCH2OH
Describe the structure of fatty acids and how we get them in our body.
- have an acid group at one end joined to a hydrocarbon chain (2-20 carbons long)
- need fatty acids to help make up our lipids. Essentially fatty acids are ones we can’t assemble ourselves so we need to absorb them whole
What does saturated means?
No double bonds in the hydrocarbon chain (raises cholesterol)
What does mono-unsaturated mean?
one C=C bond
What does poly-unsaturated mean?
more than one C=C bond
What type of bond joins a glycerol molecule to a fatty acid?
ester bond
What is the name of the molecule formed when a glycerol molecule has an ester bond to 3 fatty acid molecules?
triglyceride
How many ester bonds are there in a triglyceride?
3
What is the difference in structure between a triglyceride and a phospholipid?
Phospholipid has one phosphate group attached to the glycerol molecule (+ 2 fatty acid chains) rather than 3 in triglycerides
Describe the structure of triglycerides and how they are formed.
- 3 fatty acids each join w an ester bond to a glycerol molecule in a condensation reaction
- ester bonds form at the 3 OH groups on the glycerol
- 3 water molecules released
What can catalyse the hydrolysis of a triglyceride?
Enzymes in an organism
Are triglycerides soluble?
No, hydrophobic as charge evenly distributed on molecule
What is the structure of cholesterol and their function in organism?
- class of lipid made from 5 carbon rings
- vital to organisms, made by many cells
- hydrophobic, insoluble w water (evenly distributed charge)
- increase blood pressure when build up in blood
Why is water polar?
- H atoms each share a pair of electrons w O atom
- O more electronegative than H so pulls more on electrons away from H
- makes water dipolar
- delta - and delta + ends of water attract each other, H bonds
- v small molecule are usually gas at RT
- water molecules form up to 4 H bonds w other molecules in a network (constantly forming + reforming) making it hard for molecules to spread out enough to become gases so lots of heat needed to boil water
At what temperature is water most dense?
4⁰C
Describe how water freezes.
- temp falls so less KE
- bonds made but fewer broken
- each molecule forms 4 H bonds w other molecules making a rigid lattice
- molecules are further apart than in liquid water
- makes ice less dense than water so it floats
Why do reducing sugars change the colour of the Benedict’s solution?
donate electrons to reduce blue copper (II) ions to red copper (I) ions in copper sulphate
How are biosensors used?
- take a biological/chemical variable which can’t be easily measured + convert into an electrical signal
- can be used to detect contaminants in water + pathogens/toxins in food
- can be used to detect air borne bacteria e.g. for counter-bioterrorism programmes
