2.1.2 Flashcards
What is water formed of?
- 1 oxygen and 2 hydrogens that are covalently bonded.
- water molecules are joined by hydrogen bonding
List 8 Properties of Water
- it’s a liquid over a wide range of temperatures.
- it’s less dense when under 4 degrees centigrade.
- it’s a good solvent.
- cohesion and surface tension.
- high specific heat capacity.
- specific latent heat of vapourisation.
- it’s a reactant.
- it’s colourless with high transmission.
Why is water a liquid over a wide temperature range?
- Hydrogen bonds make it hard for water molecules to escape and become a gas so more energy is required.
What are the benefits of water being a liquid over a wide temperature range?
- can constantly move.
- can flow easily due to high viscosity.
- can be used for transport and as a medium for reactions.
Why is water less dense as ice? And what structure is formed?
Due to polar structure, the hydrogen bonds are stable and fix polar molecules at further distance than in liquid.
It makes a rigid open structure with oxygen in the middle of a tetrahedral arrangement.
What are the benefits of ice being less dense then liquid water?
- forms an insulating layer.
- if it froze from bottom up, marine life wouldn’t survive.
Why is water a good solvent?
-it’s polar so it attracts other polar substances: water molecules cluster around charged parts of solute molecules/ions, keeping them apart. Making a solution.
What molecules do and what molecules don’t dissolve in water?
- Do: ions and polar molecules.
- Don’t: non-polar molecules, triglycerides and large polymers.
How does cohesion happen?
Formation of hydrogen bonds.
Hydrogen bonds between water molecules pull them towards each other so they stick.
Surface tension of water…
…is high
And is produced by cohesion between water molecules at air-water surface as hydrogen bonds also pull molecules inwards at surface.
What does adhesion mean? Give one example.
Water molecules are attracted to surfaces.
E.g. narrow tubes in transpiration.
What does having high SHC mean?
There are no rapid temperature changes so conditions are stable in cells and aquatic environments.
Why does water have high SCH?
The hydrogen bonds between molecules absorb a lot of energy
Why does water have a high SLH of vapourisation?
Lot of energy is needed to break hydrogen bonds for it to become a gas.
What is a benefit of high SLH of vapourisation?
Used to cool organisms. E.g. sweat.
What properties of water aid in photosynthesis?
- it’s a reactant
- has high transmission so light can pass through cells for photosynthesis.
What are polymers?
Molecules that are made from a large number of monomers joined together.
What’s a condensation reaction?
Joins two molecules together with the formation of a chemical bond.
It involves the elimination of a water molecule.
What’s a hydrolysis reaction?
The separation of two molecules by breaking a chemical bond, using a molecule of water.
What chemical elements make up:
- carbohydrates
- lipids
- proteins
- nucleic acids
Carbohydrates: carbon, hydrogen, oxygen
Lipids: carbon, hydrogen, oxygen
Proteins: carbon, hydrogen, oxygen, nitrogen, sulfur
Nucleic Acids: carbon, hydrogen, oxygen, nitrogen, phosphorus
What are glucose molecules?
- a monosaccharide that has 6 carbons.
- a hexose monosaccharide
Why is glucose soluble in water?
Because it’s polar.
And is soluble in water due to hydrogen bonds between hydroxyl group and water molecule.
What is the difference between alpha and beta glucose?
Alpha glucose has the hydroxide on the first carbon under whereas beta glucose has the hydroxide on the first carbon on top.
What is an isomer?
A compound with the same chemical formula but a different chemical structure.
When does a condensation reaction happen in glucose and how?
When two hydroxides are so close they react forming a covalent bond (glycosidic bond).
Happens between first and fourth carbon.
Water is a product.
What type of bond is formed between two glucose molecules?
Glycosidic bond.
What is a monosaccharide?
- simple sugar
- general formula: (CH2O)n
What do trioses do? Give an example of one.
Intermediates in respiration and photosynthesis.
E.g. glyceraldehydes
What do pentoses do? Name two examples.
Synthesis nucleic acids, co-enzymes, ATP
E.g. ribose/ribulose
What do he hexoses do? Give two examples.
Source of energy in respiration/ building blocks for larger molecules
E.g. glucose/fructose
What is sucrose formed of?
Alpha glucose and fructose
What is maltose formed of?
Two Alpha glucose molecules
What is lactose formed of?
Alpha glucose and galactose
How do you form two monosaccharides from a disaccharide?
Through a hydrolysis reaction using one water molecule to supply H and Oh to the sugars.
What is RNA?
A single stranded polymer. (Polynucleotide).
It’s formed of nucleotides joined by phosphodiester bonds.
What is starch formed of?
Amylose and amylopectin
What is glycogen made of?
Alpha glucose
What is cellulose made of?
Beta glucose
What would happen if glucose was to dissolve in the cytoplasm?
Water potential would decrease.
Meaning water would enter by osmosis.
This can disrupt normal functioning of cell.
How is starch formed?
When alpha glucose monomers are joined by glycosidic bonds during condensation reactions.
What shape do amylose and amylopectin take?
Spiral shape, held in place by hydrogen bonds.
What makes amylose less soluble?
The OH on carbon 2 are on the inside of the spiral
Describe the structure of amylose.
Formed of alpha glucose molecules joined by 1,4 glycosidic bonds.
It’s in a helix shape due to the angle of the bonds.
Shape is held in place by hydrogen bonds.
Describe the structure of amylopectin.
It’s branched, menacing glucose can break off from multiple places to get required amounts.
1,6 glycosidic bonds happen approximately every 25 glucose subunits.
Describe the structure of cellulose.
It’s a homopolysaccharide made up of beta glucose, with 1,4 glycosidic bond.
Every other beta glucose is rotated 180 degrees.
Describe the structure of glycogen.
Made from alpha glucose that’s got 1.4 glycosidic bonds between monosaccharides except 1.6 glycosidic bonds between adjacent ones in branches
What is the function of starch?
Main storage polysaccharide in plants
What is the function of cellulose?
It’s the main structural constituent of plant cell walls.
Is strong enough to support the plant as it doesn’t have a skeleton.
What is the function of glycogen?
Main storage polysaccharide in animals and fungi.
Why is it important that glycogen is more branched?
It means it’s more compact which is important as animals are mobile than plants.
Glycogen in liver cells…
… occurs in dense granules where it can make up 7% of the liver
What are the main characteristics of lipids?
- non-polar
- hydrophobic
Why are lipids non-polar?
The electrons on the outer orbital are more evenly distributed than in a polar molecule so there are no positive/negative areas.
Making it insoluble in water.
What are triglycerides made of?
1 glycerol (an alcohol) 3 fatty acids (carboxyl acid)
How are triglycerides formed?
Through condensation reactions, also known as esterification.
What bonds are made and what is produced during the condensation reaction that makes triglycerides?
Ester bonds
3 water molecules
What are phospholipids made of?
2 fatty acids
1 glycerol
1 phosphate group
Why are phospholipids soluble in water?
The inorganic phosphate ions are negatively charged.
What part of the phospholipids are hydrophilic and hydrophobic?
Hydrophilic head.
Hydrophobic tails.
Why are phospholipids called surface active agents and what’s another name for this?
Because of their hydrophobic/hydrophilic nature, when interacting with water a layer on surface will form:
-phosphate heads in water
-fatty acid tails sticking out.
SURFACTANTS
What are saturated fatty acids?
Fatty acid chains with No double bonds between the carbon atoms.
What are unsaturated fatty acids?
Fatty acid chains with One or more double bonds between carbon atoms.
Why are UFAs liquid at room temperature?
Double bonds cause a kink or a bend.
Meaning they can’t pack together closely
What is cholesterol?
A hydrophobic organic molecule, which is a sterol.
What’s the function of cholesterol in the plasma membrane?
It sits between the hydrophobic non-polar fatty acid chains of the balayer.
It adds stability. (Structural integrity)
It regulates membrane fluidity.
Makes up 30% of plasma membrane.
Describe the structure of cholesterol.
- 4 carbon based rings, known as isoprene units.
- hydrophobic except for the OH at the end.
State 4 roles of lipids.
- membrane formation and creation of hydrophobic barriers.
- hormone production.
- electric insulation necessary for impulse transmission.
- waterproofing (leaves/birds feathers)
State 4 functions of lipids particularly triglycerides.
-buoyancy for aquatic animals.
-thermal insulation to reduce heat loss
-cushioning to protect vital organs.
Long term energy storage
Describe the general structure of an amino acid.
Has an amine group (basic)
Has a carboxyl group (acidic)
Has an R-group
What does it mean when something can act as an acid or a base in water?
Amphoteric
What are the names of monomers and polymers in proteins?
Monomers= amino acids Polymers= dipeptide and polypeptide
How does a dipeptide form?
Carboxyl group of one amino acid reacts with the amine group of the second amino acid. In a condensation reaction.
In the formation of a dipeptide what is formed?
Water.
Peptide linkage.
What is the primary structure of a protein?
Sequence in where amino acids are joined.
What bonds are present in the primary structure?
Peptide bonds
What is the secondary structure?
When the primary structure coils to form either alpha helix or beta pleated sheet
How does the secondary structure form?
Hydrogen bonds form at regions along long protein molecules depending on amino acids.
How does alpha helix form?
H.bonds form within the amino acid chains pulling it it to a coil shape
How does beta pleated sheet form?
When h.bonds form between parallel polypeptide chains.
Forming sheet like structures.
What’s the tertiary structure?
The final shape where the coiling/folding brings the R-groups of different amino acids closer enough to interact.
What are hydrophobic and hydrophilic interactions?
Weak interactions between polar and non-polar R-groups.
What are the four different interactions between R-groups in the tertiary structure?
- hydrophobic and hydrophilic interactions.
- hydrogen bonds
- ionic bonds
- disulfide bonds (disulfide bridges)
What are ionic bonds in the tertiary structure?
Between opposite,y charger R-groups, are stronger than H.bonds
Hydrogen bonds in the tertiary structure are the…
…weakest of all bonds
What are disulfide bonds?
Covalent bonds between R-groups that have sulfur atoms.
Strongest of all bonds.
What is a quaternary structure?
2 or more individual proteins called subunits.
That are joined by the same interactions in the tertiary structure.
What are three features of globular proteins?
- compact
- water soluble
- roughly spherical
How are the R-groups arranged?
Hydrophobic R-groups on amino acids are kept away from aqueous environment.
Hydrophilic R-groups are on the outside of the proteins.
Why is it good that globular proteins are soluble?
Essential for regulating many necessary life processes.
Three features of insulin:
- regulated of blood glucose concentration.
- transported in blood so needs to be soluble.
- needs to fit into specific receptors on cell surface membrane so precise shapes are needed.
What are conjugated proteins?
Globular proteins that have a prosthetic groups (non-protein component).
Two examples of prosthetic groups:
- lipids/carbs
- metal ions and molecules derived from vitamins
Why is haemoglobin a conjugated protein?
Each subunit of the protein has a haem group.
What’s haem’s function in haemoglobin?
The iron II ions combine reversibly with oxygen.
So it enables this protein to transport oxygen around the body.
What is catalase?
An enzyme.
A quaternary protein containing 4 harm prosthetic groups
What’s the haem in the catalase responsible for?
The iron II ions allow catalase to interact with hydrogen peroxide and speed up its break down.
What is hydrogen peroxide?
A common byproduct of metabolism.
It’s damaging cells/ cell components if allowed to accumulate.
Why are fibrous proteins long and insoluble molecules?
Repetitive amino acid sequence in primary structure leads to very organised structures .
What is keratin?
- hair skin nails
- has a lot of sulfur containing amino acids which make strong disulfide bonds
Name the sulfur containing amino acid…
… cysteine
Where is elastin found?
- walls of blood vessels.
- alveoli of lungs.
What is elastin made of?
A quaternary protein made from many stretchy molecules called tropoelastine
What is collagen?
- connective tissue found in skin, tendons,ligaments and nervous system.
- made up of 3 polypeptides wound together in a long and strong rope-like structure.
