Biological Molecules Flashcards
What makes water a polar molecule?
It has a partially positive hydrogen end and a partially negative oxygen end.
Why type of bond forms between water molecules?
A hydrogen bond
Why are hydrogen bonds so important?
Hydrogen bonds collectively make water very stable, meaning it can stay liquid over a large range of temperatures.
This is a vital in maintain life on Earth.
Why is water such a good solvent?
It is a polar molecule so other polar molecules and ionic compounds easily dissolve in water. This is because of the attraction between the partially positive/negative charges of water and solute.
Why do salts become hydrated?
They become surrounded by water as the water molecules have strong attraction to each other.
What is a colloid?
A colloid is when a large, insoluble molecule has water molecules weakly bound to its surface. This is important for osmotic effect.
Why does water have a high specific heat capacity?
Because of the hydrogen bonds formed between water molecules. They can absorb a lot of heat before breaking meaning water stays a liquid.
Why does ice float?
The water molecules spread out to accommodate more bond formation. This makes ice less dense than water so therefore it floats. This also means water freezes from surface down.
What are water’s cohesive forces?
Hydrogen bonding caused water molecules to stick together and to other molecules. This is what causes water and nutrients to travel from the roots to the leaves of plants.
What are the three types of carbohydrate?
- Monosaccharides
- Disaccharides
- Polysaccharides
What is the general formula of a carbohydrate?
Cx(H20)y
What is the rule for monosaccharides?
(CH2O)n where n can only be 3 to 7
What is a condensation reaction?
Where two monosaccharides are joined together and water is formed.
Carbon 1 to carbon 4 bonded via an oxygen and water is formed.
What is a reducing sugar?
A reducing sugar can reduce Cu2+ ions into Cu+ ions. (reduction is gain, Cu has gained an electron)
What is a non-reducing sugar?
They are unable to change the Cu2+ ions.
What is the Benedict’s test for reducing sugars?
- Add Benedicts reagents to your sample
- Heat in a water baths for 5mins
- If you solutions turns green, yellow or red then you have a positive test.
- Brick-red precipitate means a high conc.
- Green colour means low conc.
What is the Benedicts test for non-reducing sugars?
- Add a few drops of HCl acid to sample (be specific in exam)
- Heat sample in a water baths for 4min
- Neutralise and check with pH paper
- Perform normal Benedicts test.
What is the formula for glucose?
C6H12O6
What is the structure of alpha glucose?
1 up, 2 up, 3 down, 4 up, 5 down, CH2OH
up/down- refer to direction of hydrogen
What are the two storage polysaccharides?
Starch and Glycogen
What are the two polysaccharides that make up starch?
Amylose and Amylopectin
What is the structure of amylose?
Chains coil into a helix
alpha 1-4 glycosidic bonds
alpha glucose molecules
What is the structure of amylopectin
Highly branched
alpha 1-4 and alpha 1-6 glycosidic bonds
alpha glucose molecules
What does the starch molecule look like?
Highly branched amylopectin molecule is wrapped around the amylose. This is the starch molecule.
What is the structure of glycogen?
Highly branched polysaccharide of glucose
Has alpha 1-4 glycosidic bonds
Where is glycogen stored?
In liver and muscle cells
What turns glucose into glycogen?
Insulin
What turns glycogen into glucose?
Glucagon
What are the two structural polysaccharides?
Cellulose and Chitin
What is the structure of cellulose
Polysaccharide of beta glucose molecules, bonded with beta 1-4 glycosidic bonds.
What is the function of cellulose?
Major component of plant cell wall
Fibre of our diet
Why is cellulose good for cell walls?
Parallel chains of cellulose form hydrogen bonds with each other
Creates a molecule with rigidity and strength.
What is the structure of Chitin?
Linear polymer of N-acetyglucosamine
Has alpha 1-4 glycosidic bonds
What is the function of the Chitin?
Forms exoskeleton of insects and crustaceans
Major component in fungi cell walls
What is a lipid?
A compound that serves both as a structural and nutritional substance
What are some examples of lipids?
Fats, oils, wax, phospholipids
What are lipids formed of?
Triglycerides
What is a triglyceride?
One glycerol molecule bonded to three fatty acids.
How do you make a phospholipid?
Replace one of the fatty acids with a phosphate group
What is glycerol made up of?
Carbon, hydrogen and oxygen.
What are fatty acids composed of?
Hydrocarbon chain with a methyl group on one end and a carboxylic acid group on the other
What bonds are in a triglyceride?
The glycerol and fatty acids are bonded with an ESTER bond
What is an ester bond?
C-O
||
O
What is the test for lipids?
Add water and ethanol to your substance
Shake the tube
If a milky white emulsion appears then there is lipids present
What is a saturated fat?
There is no double bond between carbon atoms
They tend to be waxes and other solids
What is an unsaturated fat?
There is one or more double bond between carbon atoms
They tend to be oils.
Why do unsaturated fats tend to be oils?
Because they contain a double bond which mean the molecules can bend.
They can’t pack together closely and therefore are liquid at room temperature.
What are the elements for life?
Fe Iron ions N Nitrates C Carbon H Hydrogen O Oxygen P Phosphorus S Sulfur
What are calcium ions used for?
Developing strong bones and teeth
Essential for nerve transmission
Regulates heart beat
Fluid balance
What are sodium ions used for?
Function of liver and kidneys Generation of nerve impulses Fluid balance Metabolic functions Osmosis
What are potassium ions used for?
Produces electrical discharge
Neurotransmission
Heart functions
Helps plants grow healthy leaves and fruits
What are hydrogen ions used for?
Forms hydrogen bonds to create proteins
Catalysts in reactions
pH determination
What are ammonium ions used for?
Important source of nitrogen for many plants
Useful for hypoxic soil
What are nitrate ions used for?
Help plants grow healthy stems and leaves
Helps plants produce amino acids
What are hydrogen carbonate ions used for?
Maintains pH levels by stopping H+ ions having an acidic effect
What are chloride ions used for?
Essential electrolyte in all body fluids
HCl in stomach acid
What are phosphate ions used for?
Synthesis of high energy compounds such as ATP
Important for plant root growth
Backbone for bases used in DNA and RNA
Helps develop bones and teeth
What are hydroxide ions used for?
Bond with H+ ions to form water which MAINTAINS pH
Acts as a catalyst
What alkali is used to neutralise acid in non reducing sugar test?
Sodium hydrogen carbonate
What is the practical for biological molecules?
Identifying a reducing and non reducing sugar:
Four solutions A, B, C and D
Perform reducing and non reducing sugars test on each substance
State which solution is glucose (reducing) and which is sucrose (non reducing)
Other solutions are water (nothing) and protein (tiny bit of sugar)
What is the test for starch?
Add a few drops of iodine to your solution, if it turns brown then starch is present.
What colour is Benedicts reagent?
Light blue/turquoise
What colour is iodine
Orange
What is the test for proteins?
Add Biuret’s reagent
If solution turns lilac then protein is present
What is the structure of an amino acid?
A central carbon atom A hydrogen atom An R group An amine group A carboxylic group
What bond forms between amino acids?
Peptide bonds
How does the peptide bond form?
Between the carboxyl group of one amino acid and the amino group of another.
What reaction creates polypeptides?
Condensation reaction, where water is formed.
What is a long chain of amino acids called?
A polypeptide.
In what order are amino acids joined?
N-C-C backbone
What is the R group?
The group of the amino acid that determines the characteristics of the amino acid.
What characteristics can the R group affect?
Size, polarity, pH, etc.
What R group do acidic molecules have?
Carboxyl group -COOH
What R group do basic molecules have?
Amine group -NH2
What is a protein?
A protein is a molecule containing one or more polypeptide chains folded into a highly specific 3D shape.
What is primary structure?
The sequence of amino acids, with no intermolecular interactions.
What is secondary structure?
Hydrogen bonding in the polypeptide causes either an alpha helix or beta pleated sheet shape.
What is tertiary structure?
Precise 3D shape caused by a combination of bonds such as disulphides bridges, ionic bonds, covalent bonds, hydrogen bonds and hydrophilic- hydrophobic interactions.
What is quaternary structure?
Protein that is made up of more than one protein chain, e.g. haemoglobin.
What structure is the alpha helix?
Amino acid chain coils into a right-handed helix.
H bonds form between O and H atoms that are brought into close proximity
H bonds stabilise structure
What structure is beta pleated sheet?
Amino acid chain folds back on itself many times, creating anti-parallel chains.
O and H atoms form H bonds
Folded chain gives protein lots of strength.
What are globular proteins?
Usually formed from alpha helices.
Proteins that have the hydrophobic groups folded into the centre of the structure and the hydrophilic on the outside. This makes them water- soluble.
Have a spherical shape, hence ‘globular’
Why is important that globular proteins are soluble in water?
Because they act as transporters around the body and need to be able to get around the body in the bloodstream. E.g haemoglobin carries oxygen around body.
What are some function of globular proteins?
- Enzymes
- Messengers (insulin)
- Transporters
- Regulatory roles
- Structural proteins (e.g. actin, tubulin)
What bonds do globular proteins contain?
Large combination of bonds such as disulphide bridges, hydrophobic-hydrophilic interactions, covalent bonds, etc.
What is a conjugated protein?
Globular proteins that contain a prosthetic group.
What are some examples of prosthetic groups?
Lipoproteins, glycolipids are formed by prosthetic groups
HAEM group is very important in the body
What is the structure of haemoglobin?
Contains 4 chains (2 alpha, 2 beta)
Each chain contains a haem group
Haem group has a Fe2+ ion so it can pick up oxygen molecules in the lungs and transport them to the cells that need them.
What is the structure of Catalase?
- Contains 4 prosthetic haem groups
- Fe2+ ions on haem group allows it to interact with hydrogen peroxide and speed up its break down
- Works in the liver
- Prevents hydrogen peroxide (toxic byproduct of metabolism)from harming our cells.
What is the structure of insulin?
- Made up of one alpha helix and one beta pleated sheet
- Has a specific 3D shape to fit into the receptors on the cell-surface membranes
- Secreted by pancreatic cells
- Tertiary structure (lots of bonds)
- Regulates blood glucose
- 51 amino acids on each chain
What is a fibrous protein?
- Formed from long, insoluble molecules
- Secondary structure tends to be beta pleated sheet
- Contain repeating amino acids
- Very organised structures
- Tend to make strong, long molecules that are NOT folded into specific 3D shapes.
What is the structure of keratin?
Has a high proportion of cysteine and can make lots of disulphide bridges (strength)
Degree of disulphide bridges determines flexibility so hairs has fewer and nails have more
What is the structure of elastin?
- Quaternary protein
- Contains cross-links
- Found in walls of blood vessels and alveoli
- Gives structures flexibility of expand and return to normal size
- Stretch and recoil
What is the structure of collagen?
- Made up of three polypeptide chains
- Chains are tightly wound together in a rope-like structure
- Form cross-link covalent bonds
- Hydrogen bonds form between chains
- Each chain has around 1000 amino acids
- Every third amino acid is glyceine which is small and allows it to twist into a small shape
- Connective tissue found in skin, tendons, ligaments and cartilage.
- Lots of proline and hydroxyproline.
What is sucrose made up of?
Glucose and fructose
What is lactose made up of?
Glucose and galactose.
Which bonds hold the helix shape in amylose?
Hydrogen bonds
What is the importance of amylose’s helix shape?
Makes the molecule much more compact, and much less soluble
What must happen to the glucose molecules in order to bond to form cellulose?
Only way beta glucose molecules can join together is if alternate beta glucose molecules are turned upside down
What creates microfibrils?
Cellulose molecules make hydrogen bonds with each other, forming microfibrils
What are the features of the microfibrils?
- Insoluble
- Very strong
Why is cellulose so important for our health?
Because it’s insoluble, it’s very hard to break down and therefore it forms the fibre needed for a healthy digestive system
What is a colorimeter?
Equipment used to qualitatively measure the absorbance of light by a coloured solution
What is the emulsion test?
- Add a layer of ethanol
2. If white emulsion forms as a layer on top, then lipids are present
What properties of water help it to support organisms?
V1 high latent heat of vaporisation / large amount of energy
required to change from liquid to gas / AW ;
V2 evaporation is (efficient) cooling mechanism / AW ;
V3 example of cooling in living organism ;
H1 high specific heat capacity / large amount of energy needed
to, raise / change, temperature ;
H2 (thermally) stable environment for, aquatic /
named aquatic, organisms ;
H3 (aquatic) organisms use less energy on temperature
control ;
H4 (internal) temperature of organisms changes only slowly ;
H5 (biological) reactions / enzymes / metabolism, function(s)
correctly ;
Properties of water helping support organisms?
S1 (effective) solvent ; S2 medium for reactions / (internal) transport medium / able to dilute toxic substances ; C1 cohesion / adhesion ; C2 example of cohesion / adhesion, in living organism ; C2 e.g. transpiration stream / apoplast movement T1 surface tension ; T2 habitat for (named) invertebrates ; P1 transparent ; P2 allows underwater photosynthesis ; D1 idea of high density ; D2 allows flotation / support ;
Why is it important the glucose is insoluble?
So it doesn’t affect the water potential of cell its stored in
