2.1.2 - Biological Molecules Flashcards
Definition of carbohydrate
Group of substances used as both an energy source and structural material
General formula of carbohydrates
Cx(H2)y
3 main groups of simple carbohydrates
Monosaccharide
Disaccharide
Polysaccharide
Key facts about glucose
Abundant and very important
Major energy source
Highly soluble and main form of carbohydrates transported in animals
Why is glucose a hexose sugar
It has 6 carbon atoms
What does glucose exist as
Structural isomers
Common isomers of glucose
Alpha glucose
Beta glucose
What is the difference between the isomers of glucose
The OH is below the first carbon in the structure of alpha glucose whereas it is above the first carbon in the structure of beta glucose
Minor structural difference has a major effect on roles of alpha and beta glucose
Key points about fructose
Fructose is very soluble and the main sugar in fruits
It is much sweeter than glucose
Key points about galactose
It is not as soluble as glucose and fructose
It is important in making glycolipids and glycoproteins
Important pentoses
Ribose
Deoxyribose
What is the difference in the structures of ribose and deoxyribose
Ribose has a H above the second carbon and an OH below
Deoxyribose has only a H above and below the second carbon
What does the prefix ‘glyco’ tell us
It has something to do with carbohydrates
Condensation reaction
Attaching two monosaccharides by the formation of a glycosidic bond to produce a disaccharide and water
Hydrolysis reaction
Breaking the glycosidic bond in a disaccharide with the addition of water
Maltose
Glucose and Glucose
How is maltose joined
By an alpha 1-4 glycosidic bond
Sucrose
Fructose and Glucose
How is sucrose joined
By an alpha 1-4 glycosidic bond
Lactose
Galactose and Glucose
How is lactose joined
By an beta 1-4 glycosidic bond
Are monosaccharides reducing or not
Reducing
Heterogeneous
Composed of different types
Macromolecules
Molecules consisting of large numbers of atoms
Metabolism
All the chemical reactions that occur in cells
Monosaccharide
A sweet-tasting molecule consisting of a single unit
Nucleic acid
A kind of acid abundant in the nuclei of cells, includes DNA and RNA
What makes up organic compounds
Carbon and hydrogen
What are the four categories of macromolecules
Lipids
Proteins
Nucleic acids
Carbohydrates
What is a monomer
Small building blocks that make up biological molecules
Why are lipids important
Make up all of the cell membranes
Great source of energy
They don’t have a single type of monomer
Are lipids polar or unpolar
Polar
What are nucleic acid monomers
RNA
DNA
What are nucleic acid monomers made of
Nucleotides
What are the functions of nucleic acids
Carry genetic material
What differentiates amino acids
Their ‘R’ group
What are carbohydrate monomers
Sugars
Dehydration synthesis
The process of putting monomers together where water is lost and peptide bonds are formed between amino acids
Hydrolysis
Splitting apart polymers using water
What are the three parts of a nucleotide
Phosphate
5-carbon sugar (pentose)
Base
Differences between DNA and RNA
They have different bases and DNA has a double helix
4 nucleotides in DNA
Cytosine
Guanine
Adenine
Thymine
4 nucleotides in RNA
Cytosine
Guanine
Adenine
Uracil
What makes DNA anti parallel
The helixes run in different directions
How many amino acids are there
20
What determines the directionality of a protein
Carboxyl side
Amino side
Different types of lipids
Cholesterol
Free fatty acid
Triglyceride
Phospholid
What is the similar structure between all the lipids
Hydrocarbon tails
What is significant about hydrocarbons found in lipids
They’re non polar
A huge amount of energy can be released
What is unique about phospholids
It has a non polar and polar portion
Can form bilayers or micelles
What does amphipathic mean
It has a charged polar portion
What is the difference between saturated and unsaturated fatty acids
Unsaturated fats bend because they have a double bond
What determines the directionality in carbohydrates
Where the bond comes off
Amylose
Form of starch Found as granules in cells Alpha 1-4 glycosidic bond only Compact helical structure Unbranched chains
Amylopectin
Form of starch
Found as granules in cells
Glucose molecules joined by alpha 1-4 glycosidic bonds and alpha 1-6 glycosidic bonds
Branches and cannot form a helix
What is the percentage composition of starch
Amylopectin - 70-80%
Amylose - 20-30%
How is starch stored in plants
In plastids
Plastids
Intracellular starch grains in organelles
Made from green chloroplasts and colourless amyloplasts
What does cellulose stop
Cells from bursting
Structure of cellulose
Beta glucose joined by beta 1-4 glycosidic bonds
H bonds between chains
Can form micro and macofibrils
Microfibrils
Glucose in a rope like form which are then layered in a network
What is special about formation of cellulose
Every other glucose molecule molecule rotates 180 so that the hydroxyl groups are adjacent
What gives cellulose great tensile strength
Hydrogen bonds
They are very weak on their own but strong in large numbers
Glycogen compared to starch
Less dense
More soluble
Broken down more rapidly as ends are exposed
Both insoluble
Structure of glycogen
Similar structure to amylopectin but it’s more branched
Why don’t animals store starch
They store glycogen instead
What molecule is produced in the condensation of nucleotides
DNA
What molecule is produced in the hydrolysis of DNA
Nucleotides
What molecule is produced in the condensation of amino acids
Protein
What molecule is produced in the condensation of fructose and glucose
Sucrose
What molecule is produced in the condensation of glycerol and fatty acid
Lipids
What molecule is produced in the hydrolysis of protein
Amino acids
What molecules are produced in the hydrolysis of sucrose
Fructose and glucose
What molecules are produced in the hydrolysis of lipids
Glycerol and fatty acids
What are the chemical elements that make up carbohydrates
Carbon
Hydrogen
Oxygen
What are the chemical elements that make up lipids
Carbon
Hydrogen
Oxygen
What are the chemical elements that make up proteins
Carbon Hydrogen Oxygen Nitrogen Sulfur
What are the chemical elements that make up nucleic acids
Carbon Hydrogen Oxygen Nitrogen Phosphorous
What type of links are formed in the synthesis of lipids
Ester links are formed by condensation between the alcohol groups on a glycerol molecule and three fatty acids
What happens as a result of water’s polarity
Adjacent water molecules are attracted to and become bonded to each other
How are hydrogen bonds formed
The slight positive charge of a hydrogen atom of one molecule is attached to the slight negative charge of an adjacent oxygen atom
Functions of water
Transport
Chemical reactions (metabolism)
Temperature control - high latent heat of evaporation (stable environment for aquatic org.)
Support
Efficient transport medium - cohesion and adhesion
Reproduction
Transport as a function of water
Transpiration stream and water-based movement of sugars and amino acids, hormones etc. in phloem occurs in solution
Many essential metabolites dissolve completely
What is the transpiration stream held together by
Cohesion
Adhesion
Cohesion
Water molecules hydrogen bond to other molecules
Adhesion
Water molecules bind to the side of xylem vessel
Chemical reactions as a function of water
Combination of thermal stability and excellent solvent properties make water and ideal environment for chemical reactions
Water acts as a reactant for:
1) . Light dependent stage in photosynthesis
2) . Hydrolytic reactions
Support as a function of water
In plant cells water offers turgidity
In animals, water-filled tissues also contribute to skeletal support
For aquatic organisms, water provided support through buoyancy
Reproduction as a function of water
Water brings the male and female gametes together in fertilisation
Foetus develops in water filled sac
Test for starch
Iodine dissolved in KI turns from brown/orange to blue/black
Test for reducing sugars (all mono, maltose and lactose)
Benedict’s test
Add Bendicts reagent
Heat solution in water bath > 80 degrees for 5 mins
Solution turns from blue to green/ yellow/ orange/ brown or brick-red suspension
Test for proteins
Biurets test
Add NaOH
Add copper (II) sulphate solution
Solution turns from blue to purple if protein’s present
Test for lipids
Emulsion test
Add water and shake
Add ethanol to dissolve lipid
A white emulsion/ band floating near or at the top in the presence of lipids
Properties of water influenced by its polar nature
Solvent properties
Thermal properties
Cohesion tension
Specific heat capacity
Types of lipids
Triglycerides
Phospholipids
Saturated and unsaturated fatty acid
What chemical elements make up lipids
Carbon
Hydrogen
Oxygen
Components of a triglyceride
1 glycerol molecule and 3 fatty acid chains attached by Ester bonds
What are triglycerides known as
True fats or neutral fats
Characteristics of triglycerides
Rich in energy and used to store energy
Good insulators and provide buoyancy
Can be broken down in aerobic respiration and water is released
Saturated fats
Solid at room temp Only single bonds Have a lot of hydrogen Found in animals Higher melting point
Unsaturated fats
Liquid at room temp Double carbon bonds Bent (linked) Found in plants Lower melting point
Function of lipids in the body
Energy store Thermal insulation Repel water Shock absorbent Buoyant Waterproof
How do phospholipids differ in their structure from triglycerides
Phosphate group replaces one fatty acid
Why are lipids useful storage molecules
Insoluble molecules
High energy yield (2x as much as carbohydrates)
What factors do substances need to have to be ‘transport’ carbohydrates
Small
Soluble
Not reactive
What causes the colour change in the Benedict’s test
The copper is reduced by the reducing sugars to form ions
Why can’t humans digest all polysaccharides
We do not possess the appropriate enzymes
How to reverse condensation reactions
Hydrolysis reactions
Adding acid
Functions of proteins
Signalling Catalysis Structure and movement Defence and survival Transport
How do plants make amino acids
From photosynthesis and nitrate/mmonium
How many amino acids do human need
Twenty but we cannot make any of the 8/10 essential and 12/10 non essential amino acids
Why is the R group important
The Residual group is the only thing that differs in amino acids
Formation of peptide bond
Water is removed (condensation reaction)
Peptide bond is formed (covalent C-N bond)
Dipeptide
2 amino acids
Polypeptide/ protein
Many amino acids
Primary structure of proteins
Subunits held together by peptide bonds
Order determined by base sequences in DNA
Secondary structure of proteins
Folding or coiling of polypeptide chains for stabilisation
Hydrogen bonds cause polypeptide to coil into alpha helix or fold into beta sheets
What breaks hydrogen bonds
High temperature
pH change
How does a breakage of bonds affect the protein
It affects the shape and function
Tertiary structure of proteins
The secondary structure is folded into a more complex 3D shape
What is the tertiary structure stabilised by
Disulphide bonds between sulfur containing R groups
Ionic bonds between R groups
Hydrogen bonds between polar R groups
Hydrophobic/ hydrophilic interaction
Quaternary structure of proteins
Made up from multi sub-unit proteins
Held together by same bonds in 3’
Most proteins only have one polypeptide chain and so no quaternary structure
Globular proteins
Spherical and usually soluble
Hydrophobic R groups in centre, hydrophilic R groups point outside
Activity in metabolism relies on 3D shape
Shape and activity sensitive to high temp.
Why is haemoglobin a conjugated protein
It has a prosthetic group
What is a prosthetic group in a protein
An attachment not made from protein e.g. Haem
Structure of haemoglobin
All 4 polypeptide chains are attached to a haem group
What ions do haem contain
Fe 2+ ions and they bond with O2
Sub units of haemoglobin
2 alpha chains
2 beta chains
4 haem groups
Amylase
Alpha helix and beta sheets
Globular shape has an complementary active site
Active site holds Cl- (co-factor - essential for correct action)
Insulin
2 polypeptides held together by disulphide bridges
Globular protein w/ spp, fixed shape
Specific 3D shape complementary to glycoproteins receptor
Fibrous proteins
Form long strands and usually insoluble
Have structural roles in the body
Regular sequence of amino acids
Unreactive
Collagen
3 polypeptide chains wound around each other
Fibrous protein that is flexible but does not strech
Not easily stretched
Found in walls of arteries and tendons
Keratin
2 coiled polypeptide chains containing sulfur
Protect delicate things e.g. nails,claws, hair, feathers, hooves
Found in outer layers of skin cells (permeability)
Elastin
Linking tropelastin fibres
Coiled and can be stretched and recoiled
Used where stretching is required e.g. alveoli, walls of arteries, airways, bladder
Test for non reducing sugars (sucrose)
Add HCl to sample whilst heating iin a water bath > 80 degrees (to hydrolyse sample)
Add NaOH (to neutralise sample)
Then conduct test for reducing sugars
Where are peptide bonds formed
Between the hydroxide from the amine group and the H from the carboxyl group
What happens when proteins are over heated
Increased kinetic energy Molecule vibrates H bonds break Change in 3’ structure Denatures
What is thin layer chromatography used for
Separation of proteins, carbs, vitamins or nucleic acids
Starch + amylase —>
Maltose
Properties of water useful to living things
Strong cohesive forces between water molecules at the water surface mean that it is a good medium for support
H bonds attract water molecules to each other but are weak so that water molecules can move easily in relation to one another
Test for reducing sugars if using a solid
Crush the solid w/ water
Filter out the solid
Continue test as normal
Compare conc. of reducing sugars
Filter sol. and weigh ppt. formed, the heaver the ppt, the more conc.
Compare colours after benedict’s test - less accurate
Colorimetry - to find unknown glucose sol.
Make up several sol. of KNOWN glucose conc. (serial dilution)
Carry out Benedicts’s test - same vol. of reagent
Remove any ppt
Using colorimeter measure absorbance
Plot calibration curve , with glucose conc. on x and absorbance on y
How to use a colorimeter
Set up w/ red filter - no effect w/ blue
Add distilled water to cuvette to calibrate colorimeter- light should pass through clear side
Use a pippette to transfer each solution of sol. of known glucose conc into seperate cuvettes
Measure absorbance for each
Glucose bisensors
Determines conc of glucose in a solution
Glucose oxidase immobilised to electrodes, binds to and catalyses oxidation of glucose
Creates a charge which is then converted by a transducer
The electrical signal is then processed to work out the glucose conc.
Mobile phase in chromatography
Where the molecules can move
Solvent (ethanol) in bother paper and TLC
The more time spent here the faster/ further up the stationary phase
Stationary phase in chromatography
Where the molecules can’t move
Paper in paper chromatography or silica gel on a glass plate in TLC
Structure of cholesterol
Sterol
4 carbon rings w/ hydroxyl group
Hydroxyl group is polar o rest of molecule is hydrophobic
Biological roles of lipids due to their non polar nature
Membrane formation and the creation of hydrophobic barrier
Hormone production
Electrical insulation (nerves)
Waterproofing
Separating amino acids w TLC
Follow normal TLC procedure but after silica gel plate has been allowed to dry, spray w/ ninhydrin spray to give a purple/brown colour
Catalase
4’ protein w 4 haem groups
Fe2+ speeds up the breakdown of H2O2 - common by-product of metabolism but dangerous if accumulates
