Bonding Flashcards
How do hydrogen bonds form between water molecules ?
Intermolecular attraction.
Slightly positive charged atom (hydrogen) bonded with a slightly negatively barged atom (oxygen).
State 7 biologically important properties of water .
- high specific heat capacity
- high specific heat of vaporisation
- incompressible
- density
- metabolite
- surface tension and cohesion
- solvent
Incompressible
Provides turgidity in plant cells
Why does ice float on water and explain the importance for organisms?
Ice is less dense than water so it floats and acts as an insulating layer to prevent heat loss therefore aquatic organisms don’t freeze, therefore water acts as a habitat. Hydrogen bonds hold the water molecules in fixed positions further away from each other.
Why is water being a solvent important for organisms?
- molecules, ions and minerals can be dissolved in water and transported in living things.
- due to water being polar, the positive and negative charger atoms are attracted the the molecules of the solvent causing them to cluster around the solvent .
High specific latent heat and vaporisation?
SLH
• lots of energy is required to break bonds, not increase the le Eric energy of water molecules.
• acts as a buffer so it can resist fluctuations in temperature to maintain optimum temperature.
LHV
• coolant, water evaporates from skin and not loosing a lot of water
Define a monomer, examples?
Monomer is a single unit of a polymer
• amino acids
• monosaccharides
• nucleotides
Define a polymer, examples ?
Many monomers
• polysaccharides
• proteins
• dna/rna
Describe a condensation reaction with examples?
When to molecules are chemically joined together with the removal of water.
• results in a glycosidic bond
• water is a product
Describe a hydrolysis reaction with examples ?
A water molecules breaks a chemical bond betweeen 2 molecules to make separate monomers
• peptide bonds in proteins
• ester bonds in fatty acids
• glycerol in lipids
Name the elements found in carbohydrates, lipids, proteins and nucleic acids
Carbohydrates - C, H, O
Lipids - C, H, O
Proteins - C, H, O, N, S
Nucleic acids - C, H, O, N, P
Why are polysaccharides a good energy store?
- glycogen and starch are compact so there is more space in cells.
- polysaccharides hold glucose in chains so they can be snipped off via hydrolysis when needed for respiration.
•polysaccharides are less soluable than monosaccharides. Some hydrogen bonds are hidden inside away inside from the molecule.
> if glucose dissolved in the cytoplasm, the water potential of the cell would reduce and excess water would come in (flaccid).
3 disaccharides and how they form.
Maltose > 2 alpha glucose
Sucrose > glucose + fructose
Lactose > glucose + galactose
Describe the structure and functions of starch.
- Starch is made up of two polysaccharides: amylose and amylopectin
- starch grains in chloroplast and storage organs
• easily broken to release glucose in respiration
• less soluble than glucose
> larger molecule
> hydroxyl groups are hidden inside the coil
Structure of amylose
- alpha glucose monomers
- 1,4 glycosidic bond
- long coiled with helix chains stabilising the hydrogen bonds ( doesn’t affect water potential of the cell)
Structure of amylopectin
- alpha glucose
- 1,4 and 1,6 glycosidic bond
- coils similar to amylose
- branches out every 25-40 subunits
Describe the structure and function of glycogen
• alpha glucose
• 1,4 and 1,6 glycosidic bond
> 1,4 linked chains are shorter and more branched than amylopectin, making it more compact than starch.
> 1,4 are highly branched so it can be hydrolysed into glucose very quickly due to lots of branches for enzymes to attach. ( insoluble)
• forms granules in the liver and muscle cells
Describe the structure and the function of cellulose .
• polymer of beta glucose
• 1,4 glycosidic bond ( every other glucose is inverted making it a straight chain and unbranched)
> can only be broken down by a cellulose enzyme which we don’t have . Herbivores have bacteria and protoctists in the gut to break down cellulose)
• hydrogen bonds within the chain to prevent spiralling, giving cellulose its high tensile strength.
How do triglycerides form?
Condensation reaction between a glycerol and three fatty acids .
Differences between saturated and unsaturated fatty acids.
Saturated; • only single bonds • straight chain molecules • higher melting point- solid at room temperature • found in animal fats
Unsaturated; • only double carbon bonds • kinked molecules • lower melting point - liquid at room temperature • found in plant oils
Relate the structure of triglycerides to their function
- insoluble - no effect on the water potential of the cell and waterproofing
- slow conductor of heat - thermal insulation e.g stored as adipose tissue in whales acts as a heat insulator
- less dense than water - buoyancy of aquatic animals, fat is less dense than water
- energy source - can be broken down in respiration to release energy in atp. To hydrolyse the water bonds and then the glycerol and fatty acids can be broken down into co2 and h2o.
Structure and function of phospholipids.
- same as triglycerides but instead of one fatty acids it’s a hydrophilic phosphate group
- condensation reaction between and oh group and a phosphate molecule and an oh group forms an ester bond.
- forms bilayer in water
Are triglycerides and phospholipids monomers?
No they are macromolecules.
Describe the structure and function of cholesterol.
• a steroid alcohol
> not fat
> complex.
> dual hydrophobic/ hydrophilic
• adds to the stability of membranes
> hydroxyl group at periphery of membrane.
> keeps membrane fluid at room temperature.
• made in the liver and small intestines
> in bile, cholesterol can stick together to form gallstones.
> in blood, can be deposited in the inner lining in blood vessel cause aesthetic
