Biological molecules Flashcards
1
Q
How do polar molecules lead to the formation of hydrogen bonds
A
- Polar molecules = covalent molecules in substances causing an unequal share of electrons amongst the molecules hence creating regions of positivity and negativity, for example in oxygen and hydrogen there is always a larger share of electrons in oxygen - hence all hydroxyl groups including water are polar
- Polar molecules interact with each other as slightly positive region attracts slightly negative regions - this forms hydrogen bonds (which are weak)
- Hydrogen bonding
s weak but high number of bonds gives water its special characteristics
2
Q
List and explain the key characteristics of water
A
- Unusually high boiling point - water is lighter than gases (e.g. carbon dioxide, oxygen) but still it is a liquid in room temp and has a high boiling point - because of hydrogen bonding between molecules
- Ice floats - Usually substances = more dense when solid then liquid but this is the opposite for water - Happens because of how hydrogen bonds fix positions of the polar molecule further apart than in liquid state. This produces a giant rigid but open tetrahedral structure of hydrogen atoms making it less dense solid then liquid.
- Cohesive - Water moves as one mass because mols are attracted to each other (cohesion) -
- Adhesive - Water mols are attracted to other materials too which is adhesion
- Surface tension - water = more cohesive than adhesive to air causing water to have a skin of surface tension
3
Q
How does water aid life - give 6 examples
A
- Solvent - acts as solvent in which many solutes in an org can be dissolved - cytosol of prokaryotes & eukaryotes = mainly water. Many solutes inc. polar mols, amino acids, proteins, nucleic acids. This allows water to act as a medium for chemical reactions and helps transport dissolved substances in and out of cells.
- Transport medium - Cohesion allows mols to stick together in water. Adhesion and cohesion work together to exhibit capillary action which allows water to rise up against gravity
- Coolant - Helps buffer temps during chemical rxns in eukaryotic and prokaryotic because of the large amounts of energy needed to break the many hydrogen bonds in water. Maintenance of constant temp = important - to allow enzymes to work
- Constant environment - Allows fishes and animals at sea to live in water
- Ice floats - Gives insulating layer to water below which keeps temp constant and survivable allowing aquatic animals to move around, live and not be frozen
- Surface tension - Strong enough to support some animals who inhabit surface water - pond skaters
4
Q
Which chemical elements make up: Carbohydrates, lipids, proteins and nucleic acids
A
- 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
5
Q
Describe the structure and differences between pentose monosaccharide and hexose monosaccharide (including alpha-glucose and beta glucose)
A
Pentose monosaccharide = ribose
- It has 5 carbon atoms
- Lacks a carbon atom and a hydroxyl group + H on this 1 carbon compared to Hexose monosaccharide
Hexose monosaccharide = Glucose - 6 Carbon atoms - 2 types: alpha-glucose & Beta-glucose, The difference is that on carbon 1 the hydroxyl group is on opposite positions (in alpha the hydroxyl group is at the bottom, in beta it`s at the top)
See diagrams in folder
6
Q
How are disaccharides sucrose, lactose and maltose formed from glycosidic bonds
A
- Dissacharides form when two monosaccharides join together by glycosidic bond
- This is a condensation reaction
- The reaction is reversible thus it can be reversed by a synthesis reaction of hydrolysis
- Maltose is formed as two alpha glucose molecules form a glycosidic between carbon 1 - this is a 1,4 glycosidic bond
- Sucrose is formed when glucose and fructose form glycosidic bonds together
- Lactose is formed when glucose combines with galactose
7
Q
Describe and explain the structure of starch and how it`s properties relate to their functions in living organisms
A
- Made up of many bonds joined together by glycosidic bonds to form two different polysaccharides (amylose and amylopectin) which combine to create starch
- Starch is used as an energy store in plants - Release glucose for respiration - hydrolysis reaction - enzymes act as catalysts
Amylose
- formed by alpha 1,4 glycosidic bonds
- Angle of chains creates a helix which is stabilised by hydrogen bonds
- The stabilised helix makes amylose more compact and less soluble then glucose
- see diagrams in mindmap
Amylopectin
- all formed by alpha glucose
- mostly formed by 1,4 glycosidic bond, some 1,6 glycosidic bond
- 1,6 glycosidic bonds allow for branching which creates more access points for quicker energy release
- see diagrams in mindmap
8
Q
Describe and explain the structure of glycogen and how it`s properties relate to their functions in living organisms
A
- Chemical energy store in Animals and fungi
- Release glucose for respiration = hydrolysis reaction
- All formed by alpha glucose
- Mostly formed by 1,4 glycosidic bond, some 1,6 glycosidic bond but more then amylopectin
- 1,6 glycosidic bonds make it more compact thus storing more energy that animals need as they more active then plants, also allows for more access points for enzymes to add or remove glucose - speeds up process - increases respiration
9
Q
Describe and explain the structure of cellulose and how it`s properties relate to their functions in living organisms
A
- Used to form cell walls in plants, Essential for healthy digestive system as it forms necessary fibre and roughage of digestive system
- Made up of b-glucose (beta glucose) formed together by 1,4 glycosidic bonds.
Beta-Glucose bonds
- B-glucose molecules are not easily joined together because the hydroxyl groups on carbon 1 and 4 are too far apart to reach
- To counter this, alternate b-glucose molecules invert 180 degrees 0 this allows them to join and means that there are no coils or branches - just straight chains of cellulose
- Thus straight chains of cellulose are produced parallel to each other, this results in the hydroxyl groups being very close which leads to the formation of hydrogen bonds between adjacent hydroxyl groups
- Collection of thousands of hydrogen bonds = cellulose - V. Strong
- The cross-links of hydrogen bonds result in chains becoming stronger fibres
- First they bond together to form microfibrils - these join together to form microfibrilis
- These combine to form V. strong cellulose fibres
- Diagrams on mind map
10
Q
Describe and explain the structure of a triglyceride
A
- A triglyceride is made by combining 1 glycerol molecule (alcohol) with 3 fatty acids (carboxylic acids)
- Both molecules contain hydroxyl group which bond together to form ester bonds in a process called esterification (example of a condensation rxn)
- 3 Water molecules are relased as a by-product
- Diagram in folder
11
Q
What are Saturated and Unsaturated fatty acids and why are they significant
A
- Fatty acids with no double bonds between carbon atoms = saturated
- Fatty acids with carbon double bonds = unsaturated - two or more double bonds = polysaturated
one double bond - monosaturated - Presence of double bonds causes molecules to kink/bend - thus they cannot pack together as closely and remain liquid at room temp - described as oils rather than fats
- Plants contain unsaturated triglycerides as oils (usually)
- An excess in saturated fat can lead to coronary heart disease
- Excess of any type of fats leads to obesity leading to a strain on the heart
- For diagrams check folder
12
Q
Describe and explain the structure of phospholipids
A
- Contain phosphorous, Carbon, Hydrogen and Oxygen
- Inorganic phosphates ions found in cytoplasm
- Phosphate ions = extra electrons = soluble in water
- To make a phospholipid one fatty acid chain = replaced with a phosphate group
- So there are - two fatty acids, glycerol and a phosphate group
- The phosphate group is charged, making the head of the phospholipid hydrophilic but the fatty acid tail of a phospholipid is not charged and hydrophobic
- This dual hydrophobic/hydrophilic structure forms a layer on the surface of the water with it`s phosphate head in the water but the fatty acid tail sticking out of the water = surfactant/ surface active agents
- Can also form structures based on a bilayer - all hydrophilic tails point towards centre of the sheet and hence are kept away from the water.
- This allows them to separate an aqueous environment from the aqueous cytosol within cells - thus phospholipids play a key role in forming cell membranes for cells or organelles
13
Q
Describe and explain the structure, properties and function of sterols (cholestrol in particular)
A
- Type of lipid, AKA steroid alcohols
- Complex alcohol mols with a four carbon ring structure and hydroxyl group at the end
- Have dual hydrophobic/hydrophilic characteristics
- Hydroxyl groups = polar = hydrophilic
- Rest of molecules = hydrophobic
Cholestrol
- Cholesterol = sterol
- Manufactured in liver and intestines
- Important role in cell membranes - add stability and regulates fluidity - It does so by strategically positioning in between phospholipids. - keeps membrane fluid in low temp and stops it from becoming too fluid at high temp
- Vitamin D, Steroid hormones & bile made using cholesterol
14
Q
Role of lipids in the body
A
Due to being non-polar lipids have roles in:
- Membrane formation & creation of hydrophobic barriers
- Hormone production
- Electrical insulation - important for impulse transmission
- Waterproofing - bird`s feather, plant leaves
- Lipids esp. triglycerides - important role in long-term energy storage - under skin around vital organs where they provide - thermal insulation, cushioning to protect organs, Buoyancy for aquatic animals e.g. whales
15
Q
What is the general structure of amino acids and what are essential amino acids
A
R
-
(amine group) H2N —— C ——- COOH (carboxyl group)
-
H
- 20 different amino acids
- Different R group = different amino acid
- ## Essential amino acids are amino acids that have been taken in through diet because they cannot be created or converted in the body
16
Q
Synthesis and breakage of polypeptides and dipeptides
A
- Amino acids join together by forming peptide bonds with a condensation reaction
This happens by: - the amine and carboxylic acid groups connected to the central carbon atom react
- The hydroxyl in the carboxylic group reacts with a hydrogen in the amine group of the other amino acid
- A peptide bond is formed between the amino acids and water is released
- The resulting compound is a dipeptide
- When more then two amino acids are joined together a polypeptide is formed - reaction is catalysed by the enzyme - peptidyl transferase
- To break a peptide bond, a hydrolysis reaction takes place - proteases (enzyme) catalyse this reaction
