Biomolecules Flashcards
Define cell.
Building block of all living things
Made up of biomolecules
Outline the composition of cells
Water - 60%
Proteins - 16%
Triglycerides - 13%
Membrane lipids - 2.5%
Nucleic acids - 0.2%
What are the four main types of biomolecule?
- Lipids
- Carbohydrates
- Nucleic acids
- Proteins
What is a polymer?
- Large macromolecules made up of repeating units - monomers
How do biomolecules form?
- Carbon is the central atom
- Share 4 valence electrons with partner atoms C, H, O , S, P and N to form functional groups
- Functional groups on monomers join to form bonds and link, forming polymers.
What is the difference between condensation and hydrolysis?
- CONDENSATION - Endergonic (energy requiring)
- HYDROLYSIS - Exergonic - energy releasing
What do inorganic molecules not contain? Give examples.
- Don’t have carbon
- EXAMPLE: water
Describe covalent bonds.
- Interaction between atoms based on the sharing of electron pairs
- Strong with high energy so hard to break
Describe non-covalent bonds.
- May or may not involve the exchanging of electrons
- Weak with low energy so bonds are reversible - break and form constantly
Outline the order of strength of bonds.
COVALENT > IONIC > HYDROGEN > HYDROPHOBIC > VAN DER WAALS
RECAP TO A-LEVEL: What are valence electrons?
Electrons found in outermost electron shell
What are the main rules followed in covalent bonding?
- Only valence electrons used
- Outer orbitals filled to 2 or 8 electrons depending on energy level
- One covalent bond involves sharing of 2 electrons
Define electronegativity.
Power of an atom in a molecule to attract electrons towards itself
Describe non polar covalent bonds with an example.
- Equal sharing of electrons
- Atoms have similar electronegativity
- No net charge e.g C-C, C-H
Describe polar covalent bonds with an example.
- Electrons unevenly shared
- Atoms - different electronegativities
- Form dipoles e.g O-H, N-H
Define ionic bond.
Electrostatic attraction between oppositely charged ions.
Describe hydrogen bonds.
- Occur in water and in proteins and DNA
- Dipole-dipole interaction between a H and an electronegative O, N and F in another molecule
Describe van der Waals forces.
- Two types: Dipole-dipole (between polar molecules) and London dispersion (between induced polar)
- When molecules come close, electrostatic repulsion between electron shells overcomes attractive force
How do nucleotides form DNA?
- Phosphodiester bond between 5’ phosphate and 3’ OH of
sugar. Pyrophosphate released and sugar-phosphate backbone forms - Bases of 2 separate strands hydrogen bond by base pairing to form double stranded DNA. Winds to form double helix.
What determines activity of a protein?
Specific 3D structures determined by specific amino acid sequence
Give examples of proteins found in the body.
- Enzymes
- Antibodies
- Transport proteins
- Amino acid storage e.g casein
- Hormones e.g insulin
- Receptors for cell signalling
- Motile proteins e.g actin, myosin
Describe lipid solubility.
- Insoluble in polar solvents e.g water
- Soluble in non polar solvents e.g benzene
Describe the hydrocarbon chains in lipids.
- Hydrophobic
- Nonpolar
What are the three types of lipids?
- Triglycerides
- Membrane lipids
- Steroids
Where are triglycerides stored and what are they used for?
- Adipose tissue
- Energy storage
Describe the components of triglycerides.
- 1 glycerol and 3 fatty acid molecules
- Glycerol - alcohol with 3 hydroxyls
- Fatty acids - made up of carboxyl group and hydrocarbon chain that is saturated or unsaturated
Why do humans need fats?
Absorption of fat-soluble vitamins e.g Vitamins A, D, E and K
What are the differences between saturated and unsaturated fatty acids?
SATURATED - contain C-C bonds but unsaturated have C=C double bonds (causing kinks)
Describe phospholipids.
- Hydrophilic heads and hydrophobic tails
- Tails are 2 fatty acid chains
- Heads contain 1 glycerol, phosphate group and choline group
What are the functions of phospholipids?
- Structural component of cell membranes
- Regulate fluidity and permeability
What are steroids characterised by?
4 fused carbon rings
What are the functions of steroids?
- Hormones/signaling molecules
- EXAMPLE: Cholesterol - found in cell membranes
What are the functions of carbohydrates?
- Energy source for cell
- Structural roles
Describe monosaccharides.
- Chain of carbons with a -OH at each carbon except one, which forms a carbonyl group
- Classified based on location of carbonyl/number of carbons
- Form ring structures - aldehyde/keto group forms bond with one of the -OH
How do monosaccharides form polysaccharides?
- Combine in condensation reaction by forming glycosidic bonds
Describe glycogen.
- Stored in liver and muscle cells
- Energy store
- Branched - containing α-1,4 glycosidic bonds
Describe cellulose.
- Constituent of cell wall in plants
- Linear polymer
- Contains β-1,4 glycosidic bonds
