Biological Molecules Flashcards
What type of bonding occurs in water molecules and how does it arise
Hydrogen bonds form between water molecules.
Water is a polar molecule. The oxygen is electronegative so attracts the shared pair of electrons making the oxygen δ– and the hydrogens δ+.
Opposite charges attract and a hydrogen bond is formed between loan pair of electrons on oxygen and the hydrogen of another water molecule.
What are some properties of water
High specific heat capacity High latent heat of vaporisation Ice is less dense then water Solvent, medium Cohesion, adhesion Surface tension
Explain waters high specific heat capacity
A large amount of energy is required to increase waters temperature by a degree
Therefore water can act as a stable environment or be involved in reactions acting as a buffer
Explain waters high latent heat of vaporisation
A large amount of energy is required to evaporate water. This is due to the strong hydrogen bonds between water molecules.
As a result water can act as a coolant as it removes a lot of heat when it evaporates
This is why dogs pant and some animals put saliva on their armpits
Why is ice being less dense then water
Ice is less dense then water so it floats. It can act as an insulting layer so animals don’t freeze underneath
It can also provide a habitat on top of the ice
How can water at as a solvent
Being a polar molecule it can dissolve a range of charged substances and transport them around the body and elsewhere
For example oxygen can dissolve in water making it accessible to aquatic life
Opposite charges surround and seprarate ionic compounds into their ions
Explain waters cohesive (surface tension as well) and adhesive nature
Water molecules are attracted to each other so can provide surface tension. This can be a habitat for species like pond skaters
Water molecules also get attracted to for example the walls in the xylem. This is called adhesion and provides a long continuous column of water that can be transported up the plant.
What is a monomer and a polymer
Monomer single unit eg nucleotides
Polymer multiple repeating units of monomers eg nucleic acids
What is a condensation and a hydrolysis reaction
Condensation - Two substances combine forming a bond and a by product of water
Hydrolysis - Adding water to a substance to break a bond
What atoms do carbohydrates consist of how do you test for it
C H O
What type of sugar is glucose
Hexose monosaccharide
What are the two types of glucose what are the structural differences
α-glucose
β-glucose
With alpha glucose on Carbon 1 the hydrogen atom is above the hydroxyl group
With beta glucose on Carbon 1 the hydroxyl group is above the hydrogen atom
What are the two types of pentose sugars that can be present in DNA and RNA
Deoxyribose and Ribose
How are disaccharides formed what is the bond called
2 monosaccharides join together and a glyosidic bond is formed between Carbon 1 and Carbon 4 (alpha 1,4 glycosidic bond) and molecule of water is released
What is disaccharides are Lactose, Sucrose and Maltose formed from
How do you test for these
Lactose - Glucose and Galactose
Sucrose - Glucose and Sucrose
Maltose - 2 Glucose
Reducing sugars - Add benedict’s reagent blue to brick red if positive
Non reducing sugars - Add dilute HCL and NaOH and boil and perform testing for reducing sugars as normal. Sucrose is an example
What is Starch comprised of in plants how can you test for this
Amylose - Contains alpha 1,4 glycosidic bonds it is a chained molecule but can coil up to make it compact
Amylopectin - contains alpha 1,4 and alpha 1,6 glycosidic bonds. This makes the molecule more branched. This is useful as there’s more ends for the enzymes to break down to release energy
To test for this add iodine orange to black is positive
What is glycogen comprised of how does this compare to mainly amlyopecitin in starch
Similar structure to amylopectin, it contains 1,4 and 1,6 alpha glyosidic bonds, however it contains more 1,6 making it more branched.
This is as mammals typically have a higher metabolic so demands are much higher. Glycogen needs to be broken down much quicker as a result
Why is glucose stored as starch and glycogen inside cells
It’s insoluble so doesn’t affect osmotic potential and is compact so more energy dense
Describe the structure of glucose
Long and unchained due to the beta 1,4 glycosidic bonds. Being beta glucose to form the bonds every other glucose is flipped 180 degrees so a straight chain is formed.
Cellulose chains can form cross links and hydrogen bonds between fibrils. This gives cellulose HIGH TENSILE STRENGTH. It’s also insoluble
What atoms to lipids consist of
CHO(P)
P is present in phospholipids
Give some properties of lipids
Energy storage due to many C-H bonds Structural component - phospholipid bilayer and glycolipids Electrical insulator - myelin sheath Buoyancy Waterproofing
What are the components of triglycerides what are the bonds formed
One glycerol and 3 hydrophobic fatty acids tails
3 ester bonds are formed releasing 3 molecules of water
What is the difference between a saturated and an unsaturated triglyceride
Saturated - Contains no double bonds usually solid (fats) and room temp
Unsaturated - Kinked due to double bonds so less intermolecular forces between hydrogen
bonds. Usually liquid (oils) at room temperature. Has a lower melting point as
a result
Why do camels store fat in their humps
Triglycerides are rich in energy and when required can be broken down in aerobic reparation also releasing water which is useful for animals in dry conditions
Describe the structure of a phospholipid
1 phosphate group which is hydrophilic
2 fatty acids tails that are hydrophobic
Forms phospholipid bilayer only lipid soluble can pass through
Increased fluidity if tails are kinked
How do you test for lipids
Emulsion/Precipitation
Add ethanol to your sample and shake then pour into water and a milky white ppt should be visible
What atoms does proteins consist of
CHON(S)
S if the amino acid cysteine is present
What is the general structure of an amino acid
R
|
H2N—–C—-COOH
|
H
What bond is formed between 2 peptides
Peptide bond is formed water is released
What are the 4 structures of proteins
Primary - Sequence of amino acids
Secondary - Alpha helix and beta pleated sheet influenced by hydrogen bonds
Tertiary - 3D structure influenced by disulphide bridges , hydrophobic interactions and ionic
bonds
Quaternary - Multiple polypeptide chains
What is a globular protein give some examples
3D spherical in shape and is soluble tend to have functional features
Examples include enzymes, antibodies, hormones and haemoglobin
Haemoglobin has a quaternary structure and is a conjugated protein as it contains a prosthetic group called haem (Fe2+ )which is non protein
It’s soluble as it has hydrophilic r groups on the outside
What is a fibrous protein give some examples
Long unchained usually unreactive and insoluble in water tend to have structural features
Hydrophobic r groups on the outside
Examples included collagen, keratin and elastin
Collagen - 3 polypeptide chains wound around each other, every 3rd aa is glycine
forms crosslinks between fibrils giving it HIGH TENSILE STRENTH in walls of arteries
Keratin - 2 polypeptide chains protects delicate parts of the body
Elastin - Can stretch and recoil. Found in walls of alveoli
How can you make the benedict’s test more quantitative
Use benedict’s reagent can be subjective
Use colorimeter
Plot a calibration curve with known concentrations or prepare using a serial dilution
To calibrate your colorimeter use a blank (distilled water)
Use a red filter
Pour sample in a cuvette and place in colorimeter to obtain absorbance
Read across from your graph (absorbance against concentration ) to identify the concentration
