SPEC - P1 - M2: BIO MEM Flashcards
(a) how hydrogen bonding occurs between water
molecules, and relate this, and other properties
of water, to the roles of water for living
organisms (9)
- forms hydrogen bonds between H and O
Ice is less dense than water
Ice will float and insulate the water underneath
The whole body of water does not freeze
Water has a high specific heat capacity
Because the hydrogen bonds can absorb a lot of energy
Therefore it is thermally stable
Good habitat, particularly for ecotherms
Water has a high latent heat of evaporation
Because it takes a lot of energy to break the hydrogen bonds
Therefore, can be used to cool organisms via sweating
Water has high cohesion
Because it is a polar molecule
Therefore it flows by mass flow through the xylem and phloem
Water is a good solvent
Because it is a polar molecule
Therefore ions and glucose easily dissolve and can be transported
(b) the concept of monomers and polymers and
A: Describe the difference between a monomer and polymer. Give an example of each. (4)
A: A monomer is a small, basic molecular unit.
For example an amino acid, monosaccharide or nucleotide.
A polymer is a large, complex molecule made up of lots of monomers bonded together in a long chain.
For example proteins, polysaccharides and nucleic acids
(b) the importance of condensation and hydrolysis
reactions in a range of biological molecules: Condensation vs Hydrolysis
Condensation:
Two molecules are bonded together
A covalent bond is formed
Water is formed as a by product
From the OH from one molecules and the H from the other
Hydrolysis:
A larger molecule is split into two smaller ones
A covalent bond is broken
Water is added
To form the OH of one molecules and the H of the other
(c) the chemical elements that make up biological
molecules: carbohydrates, lipids, proteins, nucleic acids
C, H and O for carbohydrates
C, H and O for lipids
C, H, O, N and S for proteins
C, H, O, N and P for nucleic acids
(e) the synthesis and breakdown of a disaccharide
SYNTHESIS:
Condensation reaction
Forms a 1,4 – glycosidic bond
Water is formed
From a hydrogen atom of one sugar and a hydroxyl group (OH) from the other
BREAKDOWNS:
Hydrolysis reaction
Breaks a 1,4 – glycosidic bond
Water is needed for the reaction
Adds a hydrogen atom to one sugar and a hydroxyl group (OH) to the othe
give three disaccharides
sucrose
maltose
lactose
State the monosaccharides present in these disaccharides:
Sucrose
Lactose
Maltose
Sucrose – One alpha glucose molecule, one fructose molecule
Lactose – One beta glucose molecule and one galactose molecule
Maltose – Two alpha glucose molecules
(f) the structure of starch (amylose and
amylopectin)
Polysaccharide of alpha glucose
A mixture of amylose and amylopectin
Amylose is unbranched chain of alpha glucose molecules
All 1,4 – glycosidic bonds
Coiled structure
Amylopectin is branched
Contains 1,4 and 1,6 – glycosidic bonds
(f) the structure of glycogen (3) and cellulose molecules (6)
Glycogen:
Polysaccharide of alpha glucose
Lots of branching
Contains 1,4 and 1,6 – glycosidic bonds
Cellulose:
Polysaccharide of beta glucose
Alternate beta glucose molecules are flipped over
Forms straight cellulose chains
Cellulose chains bonded together with hydrogen bonds
This forms microfibrils
Microfibrils join together to form macrofibrils
(g) how the structures and properties of glucose relate to
their functions in living organisms
Soluble – therefore easily transported
The chemical bonds contain a lot of energy
(g) how the structures and properties of
starch relate to their functions in living organisms
Insoluble – doesn’t affect the water potential of the cell
The coiled structure of amylose makes it compact
Can store a lot of starch in a small space
The branches of amylopectin allow enzymes to hydrolyse it quickly
Glucose can be released more quickly
(g) how the structures and properties of glycogen relate to
their functions in living organisms
Insoluble – doesn’t affect the water potential of the cell
Compact – can store a lot in a small space
Lots of branches allow enzymes to hydrolyse it quickly
Glucose can be released more quickly
(g) how the structures and properties of cellulose molecules relate to their functions in living organisms
Many hydrogen bonds provide structural strength
Necessary for the cell wall
(h) the structure of a triglycerides (5)
One glycerol molecule
Three fatty acids tails
The fatty acids can be saturated or unsaturated
Saturated fatty acids only contain single bonds between the carbon atoms
Unsaturated fatty acids have at least one double bond between the carbon atoms
(h) the structure of a phospholipid
One glycerol molecule
One phosphate group
Two fatty acid tails
The phosphate group is hydrophilic and the fatty acids are hydrophobic
(i) the synthesis of triglycerides by
the formation (esterification)
A condensation reaction occurs
Between the glycerol molecule and the fatty acids
A hydrogen atom is removed from the glycerol
An OH group is removed from the fatty acids
To form three molecules of water
An ester bond is formed
(j) how the properties of triglycerides molecules relate to their functions in living organisms/ Describe the functions of triglycerides and explain how their structure aids the function
Energy storage molecules
They are insoluble
And therefore don’t affect the water potential of the cell
The fatty acid tails contain a lot of chemical energy
This energy is released when the bonds are broken
(j) how the properties of phospholipid
molecules relate to their
functions in living organisms/ Describe the functions of phospholipids and explain how their structure aids the function
Form the bilayer in membranes
The phosphate heads are hydrophilic and the fatty acid tails are hydrophobic
Therefore the phosphate heads face outwards and the tails face inwards
The fatty acid tails act as a barrier to water soluble substances
(j) how the properties of cholesterol
molecules relate to their
functions in living organisms/ Describe the functions of cholesterol and explain how their structure aids the function
Strengthen the cell membrane
Small, flat shape
Therefore, it can fit in between the tails of the fatty acids in the membrane
The cholesterol can bind to the tails of the phospholipids
Therefore making the membrane less fluid and more rigid
(l) the synthesis of dipeptides
SYNTHESIS:
Condensation reaction
The OH of the carboxylic acid group in one amino acid bonds with a H atom from the amino group of the other amino acid
This produces water
Forms a peptide bond
(m) the levels of protein structure
primary, secondary, tertiary and
quaternary structure
Define the term primary structure. (1)
The sequence of amino acids in a polypeptide chain
Describe how the secondary structure of a protein is formed. (2)
The polypeptide chains coil to form an alpha helixes
Or fold to form a beta pleated sheet
Describe how the tertiary structure of a protein is formed (include details of the different bonds that hold the protein in its tertiary structure). (5)
The alpha helixes and beta pleated sheets coil and fold further.
Held in place by lots of bonds:
Ionic bonds between amino acids of opposite charge
Hydrogen bonds between amino acids with slight charges
Disulphide bonds that form between sulphur atoms in two cysteine amino acids
Hydrophilic interactions – hydrophilic amino acids are found on the outside of the protein.
