Chap.1 Chemical elements and biological compounds Flashcards
Use of Mg2+
Constituent of chlorophyll, for photosynthesis
Otherwise chlorosis and stunted growth in plants
Use of Fe2+
Constituent of haemoglobin
Use of Ca2+
Structural component in bones, teeth
Also in cell walls to give strength
Use of PO4 3-
Nucleotide production e.g. ATP
Constituent of phospholipids
Why is water a dipole?
A dipole means that the molecule is polar, and it has a positive and negative charge separated by very small distances
No overall charge
H+ ions are slightly electronegative and O2- ions are more electropositive
Type of bonding between H2O molecules
Hydrogen bonding
Why is water a good solvent
It is polar
so attracted charged particles and other polar molecules
What is good about water being a solvent
Act as a transport medium e.g. in xylem and phloem in plants
Chemical reactions taking place in water (aq)
Why water has a high specific heat capacity
Hydrogen bonding collectively strong
Requires large amount of energy
Why is water having a high specific heat capacity good
No large fluctuations of temp in water
Stable habitat
Enzymes work efficiently
Organisms do not have to adapt to extreme conditions
Why is water having a high latent heat of vaporisation good
In temperature control mechanism
Releases energy when sweating, cool down body
What is cohesion in water
Attraction between water molecules
Sticking together as a lattice
So columns of water drawn up xylem vessels
How does the high surface tension in water help some organisms
Insects able to skate through
What is special about density of liquid water and ice
Ice is less dense than water
So float on water if temp drops
as it has to expand when more hydrogen bonds form
Therefore a thermal insulation preventing water beneath to freeze
Organisms at the bottom survive
What is important about water being transparent
So light can pass through
Aquatic plants photosynthesise efficiently
General formula of a monosaccharide
CH2O
What is the category of monosaccharide glucose is in
Pentose sugar (six rings)
Names of isomers of glucose
Alpha and Beta glucose
Have same chemical formula but different molecular arrangements
Functions of monosaccharides
- Energy source from respiration
- Building blocks for larger molecules
- Intermediates in reactions
- Constituents of nucleotides
What is a disaccharide
2 units of monosaccharides bonded together
How is a disaccharide formed
By condensation reaction
1, 4 Glycosidic bonds in between
Elimination of water
Maltose = ?
Alpha glucose + Alpha glucose
Sucrose = ?
Alpha glucose + fructose
Lactose = ?
Beta glucose + galactose
Test for reducing sugar
Add Benedict’s solution and heat
If color changes from blue to brick red, reducing sugar is present
Why sucrose gets a negative result when using Benedict’s solution
As it is a non-reducing sugar
Test for non reducing sugar using Benedict’s solution
Add acid (HCl) and heat
Add alkali e.g. NaOH and Benedict’s solution
as Benedict’s solution works in alkaline conditions
If color changes from blue to brick red, reducing sugar is present
How to detect sucrose apart from using HCl
Use of sucrase (enzyme)
Benefits of starch as storage comparing to glucose
Insoluble in water
so no osmotic effects
More compact so can store a lot is a small space
Carries a lot of energy
What is the main store of glucose in plants
Starch
Two types of starch
Amylose and amylopectin
Describe amylose
Bonded by alpha 1,4 glycosidic bonds
Coiled into helices
Describe amylopectin
Has both alpha 1,4 and 1,6 glycosidic bonds
Test for starch
Add iodine solution (iodine potassium test)
Color changes from brown to dark blue
Main energy storage in animals
Glycogen
Describe glycogen
Similar to amylopectin
Has both alpha 1,4 and 1,6 glycosidic bonds
But more branches/break ends
So more energy could be stored
More suitable for high metabolic needs in animals
What is cellulose consisted of
beta glucose units
Structure of cellulose
Beta glucose monomers joined by 1,4 glycosidic bonds
But alternating unit every adjacent molecule
of 180 degrees
Parallel hydrogen bonding between chains
so form microfibrils
Usage of cellulose
Found in plant cell walls
Provides strength to withstand pressure (from osmosis)
Structural stability
Where is chitin found
- Exoskeleton of insects
2. Fungi cell walls
Structure of chitin
Similar to cellulose
Beta 1,4 glycosidic bonds
Plus an amino group
Rotating 180 degrees, alternating adjacent monomers
Crosslinks and microfibrils (hydrogen bonding)
What is consisted of a triglyceride
1 glycerol and 3 fatty acids
How is a triglyceride made
Each glycerol joined by 3 fatty acid tails
by condensation reaction
Forms ester bonds for each tail
Elimination of water
Property of lipid
Insoluble in water, but soluble in organic solvents e.g. ethanol
What does a phospholipid contain
1 phosphate group, 2 fatty acid chains, 1 glycerol
Properties of a phospholipid
Phosphate head is hydrophilic, attracted to water
Fatty acid tails are hydrophobic, non polar, repel away from water
Difference between a saturated and an unsaturated fatty acid chain
Saturated: Contains the max number of carbon atoms
Unsaturated: bend in directions, monomers do not align uniformly
Properties of a lipid with mostly unsaturated fatty acids
Oil at room temp, as lipid doesn’t solidify readily
Roles of phospholipids
- Cell membranes
2. Electrical insulation
Uses of triglycerides
- Energy storage
- Thermal insulation
- Physical protection
- Produces metabolic water from condensation
Test for lipid
Mix solution with ethanol
*Shaken with equal volume of water
White emulsion formed
Consequences of diet high in saturated fats
Build up of low density lipoproteins
Carries fats to arteries for deposit
Fatty materials can build up to block blood flow
May lead to heart attack, angina
Why is HDL good
Made when diet has a higher proportion of unsaturated fats (plant oils)
Transports harmful fats to liver for disposal
Lower risks of cardiovascular diseases
What element is only contained in proteins, not in lipids or polysaccharides
Nitrogen
What is a polypeptide made of
amino acid chain
Formation of a dipeptide
Elimination of water, OH from carboxyl group of one amino acid, H from amine group of another
Peptide bond
by condensation reaction
Primary structure of protein
Unique sequence of amino acids
held by peptide bonds
Sequence determined by DNA
Secondary structure of protein
either alpha helices or beta pleated sheets
hydrogen bonding
Initial 3D shape
Tertiary structure of protein
Mixture of alpha helices and beta pleated sheets Gives complex 3D structure of a protein Bonding: 1. disulphide bridges 2. hydrogen bonding 3. ionic bonding 4. hydrophobic interactions
Quaternary structure of protein
More than 1 polypeptide chain
or bonded with non-protein groups
e.g. haem Fe2+
to be functional
Properties of fibrous proteins
Insoluble in water
Many cross links and long fibres
Strong and tough, provides strength
E.g. collagen, keratin
Properties of globular proteins =
Soluble in water
Spherical in shapes
E.g. enzymes
Test for proteins
Add Biuret solution
Color changes from blue to purple
Diagrams check!
- Amino acid -> dipeptide
- Triglyceride
- Alpha/Beta glucose
