Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

biology A-level > 2.1.2 biological molecules > Flashcards

2.1.2 biological molecules Flashcards

You may prefer our related Brainscape-certified flashcards:
AP® Biology flashcards Biology 101 flashcards
1
Q

why is water important

A
  • all metabolic reactions in cells take place in water (cytoplasm, vacuole/sap)
  • 71% of the earth’s surface is covered in water, making it a major habitat
  • 70-95% of a cell’s mass is water
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

what are hydrogen bonds and how do they form

A
  • as a result of the polarity of molecules such as water, the
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

what is the charge of a water molecule

A
  • electrically neutral as a whole, but is a dipole, polar molecule
  • the oxygen atoms are more electronegative than hydrogen, resulting in a weak negative electric charge as they attract electrons more strongly (δ-)
  • hydrogen is electronegatively weaker than oxygen, forming a slight positive charge (δ+)
  • this means that the covalently shared electrons are closer to the oxygen atom (polar covalent bond)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

what is the shape of a water molecule

A
  • due to waters polarity, its shape is asymmetrical
  • there is about 105 degrees between the hydrogens
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

what are hydrogen bonds and where/how do they form

A
  • hydrogen bonds form between the δ+ and δ- ends of polar molecules such as water
  • they are weak by themselves, so constantly break and reform, but form strong structures when in larger numbers
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

what are the main properties of water

A
  • a universal solvent (will be able to dissolve any polar molecule)
  • acts as a transport medium
  • has a high specific heat capacity
  • has a high latent heat of vaporisation
  • less dense in solid form (ice floats on water, which provides an insulating layer and acts as a habitat for animals e.g. polar bears, underwater flora)
  • high surface tension (adhesion) and cohesion (transpiration stream)
  • can act as a reagent
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

why is water a good solvent and what does it allow

A
  • as it is polar, many polar substances and ions can dissolve in it as they compete with hydrogen bonds
  • e.g. Na+ and Cl- ions, glucose, amino acids
  • this allows chemical reactions to occur within cells (as the dissolved solvents are more reactive as they are free to move in aqueous form)
  • hydrophilic (polar) metabolites (chemical substances involved in metabolism) can be transported efficiently
  • prokaryotes can exchange nutrients and waste substances with their surroundings via diffusion
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

why does water have a high SHC and what does it allow

A
  • has a specific heat capacity of 4200 J/kg°C
  • the many hydrogen bonds between the polar molecules require a lot of thermal energy to break and a lot of energy to build
  • this means that water temperature does not fluctuate greatly or very quickly
  • this provides a stable habitat for aquatic organisms in lakes and oceans, and maintains temperatures that are optimal for enzyme activity in both prokaryotes and eukaryotes
  • water in blood plasma helps to transfer heat around the body, as thermal energy is absorbed, but does not change temp much
  • water is also in tissue fluid, playing a role in maintaining constant body temperature
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

why does water have a high latent heat of vaporisation and what does it allow

A
  • a large amount of thermal energy has to be absorbed to break hydrogen bonds to cause the molecules to evaporate
  • only a small amount of water needs to be lost by organisms to lose a lot of thermal energy
  • provides a cooling effect for living organisms (thermal energy lost due to sweat evaporation, transpiration through stomata in leaves)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

what is cohesion and what does it allow

A
  • hydrogen bonds between the δ+ (hydrogen) and δ- (oxygen) ends of water molecules on the surface of the water
  • this provides strong surface tension on water, meaning many small invertebrates (pond skaters etc.) can float
  • cohesion also allows water to move through xylem and blood vessels, as water can climb up to 1m in tubes (the smaller the diameter of the tube, the higher it can climb)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

what is adhesion and what does it allow

A
  • hydrogen bonds/intermolecular associations between water and other molecules (such as cellulose and lignin)
  • allows movement up the transpiration stream as the water adheres to the lignin walls of xylem
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

what elements are in carbohydrates and what is their general formula

A
  • Carbon, Hydrogen, Oxygen
  • Cx (H2O)y
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Lipids consist of…

A

Carbon, Hydrogen, Oxygen, sometimes Phosphorus (however has very little Oxygen compared to carbs)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

nucleic acids consist of…

A

Carbon, Hydrogen, Oxygen, Nitrogen, Phosphorus

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

proteins consist of…

A

Carbon, Hydrogen, Oxygen, Nitrogen, Sulfur

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

carbohydrates- monomers and polymers

A

monosaccharides (glucose, fructose, galactose)
di/polysaccharides (starch, cellulose)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

proteins- monomers and polymers

A

peptides/amino cids
polypeptides

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

lipids- monomers

A

phosphates, fatty acids, glycerol

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

nucleic acids- monomers and polymers

A

nucleotides (deoxy/ribose sugar + phosphate + nitrogenous base)
DNA, RNA

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

what is a condensation reaction

A

when monomers join together to form a polymer or macromolecule, releasing water and making a covalent bond- can be catalysed by enzymes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

what is hydrolysis

A

when water is used up, the larger polymer or macromolecule will split up into monomers/smaller molecules, the covalent bond is broken- can by catalysed by enzymes

20
Q

what are macromolecules

A
  • very large molecules with a high molecular mass, 1000+ atoms
  • polymers can be examples of macromolecules
  • phospholipids are examples of macromolecules
  • polysaccharides are macromolecules as well as polymers
21
Q

what bonds do carbohydrates form in a condensation reaction

A

glycosidic bonds

22
Q

what bonds do proteins form in a condensation reaction

A

peptide bonds

23
Q

what bonds do lipids form in a condensation reaction

A

ester linkage

24
Q

what bonds do nucleic acids form in a condensation reaction

A

phosphodiester

25
Q

what is an organic compound

A
  • a compound/molecule containing Carbon and Hydrogen
  • carbon can form four covalent bonds
  • they can form covalent bonds with Oxygen, Hydrogen, Sulfur and Nitrogen
  • they can form straight chains, branched chains, or carbon rings
26
Q

what are the functions of carbohydrates

A
  • good source of energy (glucose is used for energy release during respiration)
  • store of energy (glycogen is stored in muscles and liver as insoluble glucose)
  • structural importance (cellulose in cell walls of plants)
27
Q

what is a monosaccharide (definition, example, function)

A
  • a single sugar monomer, which are reducing sugars
  • three types: triose, pentose, hexose
  • triose: glyceraldehyde (3 carbons)
  • pentose: deoxy/ribose (5 carbons)
  • hexose: glucose, fructose, galactose (6 carbons)
  • act as sources of energy in respiration, are monomers
28
Q

what is a reducing sugar and how are they detected

A
  • a sugar which acts as a reducing agent in a chemical reaction i.e. donates an electron to another atom
  • therefore, the sugar itself is oxidised
  • they can be detected using the Benedict’s test, where blue, soluble CuSO4 is reduced into brick red, insoluble copper oxide precipitate
  • the Benedict’s test is somewhat quantitative, as the colour can either turn green, yellow or orange as well depending on how much reducing sugar is present
  • the solution can then be put through a colorimeter to obtain a numerical value for light transmission
29
Q

what is a disaccharide (definition, example, function)

A
  • a sugar formed from 2 monosaccharides joined by a glycosidic bond in a condensation reaction
  • maltose (α glucose + α glucose)
  • sucrose (α glucose + fructose)
  • lactose (α glucose + β galactose)
  • sugar found in germinating seeds (maltose)
  • mammal milk (lactose)
  • stored in sugar cane (sucrose)
30
Q

what is a polysaccharide (definition, example, function)

A
  • a polymer formed by many monosaccharides joined by a glycosidic bond in a condensation reaction
  • cellulose (β glucose)
  • starch (α glucose in amylose + amylopectin)
  • glycogen (α glucose)
  • energy storage (insoluble starch and glycogen)
  • structure (cellulose cell wall)
31
Q

what are the functions of lipids

A
  • source of energy (when respired, have high energy yield- 2x carbs)
  • store of energy (stored in animals as fats in adipose tissue, in plants as lipid droplets in seeds, oils)
  • insulating layer (thermal insulation under the skin, blubber, electrical insulation in myelin sheath
  • biological membranes (phospholipid bilayer)
  • protection (around organs acting as shock absorber, leaved have waxy cuticles)
32
Q

what is the difference between alpha and beta glucose

A
  • glucose is an isomer
  • the difference between the glucoses is the arrangement of the OH and the H on the Carbon-1 atom (right hand side of molecule)
  • they both have six membered rings
  • α glucose has the OH group below the plane
    -β glucose has the OH group above the plane
33
Q

what are the functions of proteins

A
  • cell growth, cell repair, replacement of biological materials
  • structurally important (muscles, collagen and elastin in skin, keratin in hair)
  • carrier molecules in cell membranes
  • glycoproteins in cell membranes (antibodies, cell signalling)
  • enzymes and hormones
34
Q

how can you detect non-reducing sugars

A
  • they cannot donate electrons/be oxidised and therefore are not reducing agents
  • they must first be hydrolysed to break the disaccharide into two monosaccharides before a Benedict’s test can be carried out to identify the reducing sugar monomers
  • add dilute HCl to the sample and heat in a boiling water bath
  • neutralise the solution (make slightly alkaline) with sodium hydrogencarbonate and an indicator e.g. red litmus paper (purple when neutral)
  • e.g. sucrose
35
Q

what is an isomer

A

organic molecules with the same molecular formula but different structures, resulting in different properties

36
Q

what is the difference between ribose and deoxyribose sugars

A
  • ribose sugars have an OH group on the lower plane of the Carbon 2 atom
  • deoxyribose sugars have lost an oxygen, meaning there is only a Hydrogen on the lower plane of the Carbon 2 atom
37
Q

how and why are glycosidic bonds formed

A
  • make monosaccharides more suitable for transport, storage and to have less influence on a cell’s osmolarity (blood sugar levels)
  • two OH groups on saccharides interact to each form a covalent bond between one Oxygen
  • this is a condensation reaction, so releases water (H2O)
  • there are either 1-4, 1-2 or 1-6 glycosidic bonds (maltose/cellulose/amylose, sucrose, amylopectin)
38
Q

what is the structure of starch

A
  • 10-30% amylose (unbranched helix-shaped chain with only 1-4 glycosidic bonds between α glucose molecules)
  • they are helix shaped in order to be more compact and thus resistant to digestion
  • 70-90% amylopectin (1-4 glycosidic bonds between α glucose, and also 1-6 glycosidic bonds, forming a branched molecule) – 1-6 glycosidic bond around every 20th molecule
  • the branches are easily broken off and provide an efficient release of glucose when necessary
  • the outermost glucose molecules on branches are called terminal glucose molecules
39
Q

what is the function of starch

A
  • an insoluble source of carbohydrates/glucose in plants so does not affect osmolarity of cells
  • is branched to pack in many molecules as well as easy to break off for quick glucose release for respiration for energy
  • is stored as granules in membrane-bound plastids (amyloplasts)
  • starch takes longer to digest than glucose due to its compactness
40
Q

what is the function of glycogen

A
  • insoluble storage of glucose in animals (found in muscle cells, kidney, liver as granules in high concentration), fungi and bacteria
  • does not affect osmolarity of cells by maintaining soluble glucose levels
  • is branched to pack in many molecules as well as easy to break off for quick glucose release for respiration for energy
41
Q

what is the structure of glycogen

A
  • made of only α glucose molecules
  • 1-4 glycosidic bonds as well as 1-6 glycosidic bonds, creating a heavily branched molecule
  • 1-6 glycosidic bond around every 10th molecule
42
Q

what is the structure of cellulose

A
  • only β glucose, joined together by 1-4 glycosidic bonds
  • however, β glucose is an isomer of alpha glucose, meaning every other β glucose must be rotated 180° to form a 1-4 bond
  • this means that cellulose strands are incredibly straight, many hydrogen bonds form between the chains, giving it high tensile strength
43
Q

what is the function of cellulose

A
  • main structural component of cell walls due to its high tensile strength
  • many hydrogen bonds between cellulose strands (approx. 50 nm wide) microfibrils (60-70 cellulose strands), fibrils and macrofibrils
  • allows plant cells to withstand turgor pressure
  • form a matrix/mesh which increases strength and maintains cell structure
  • freely permeable walls to allow molecules to the cell membrane
  • not many organisms have the enzyme (cellulase) to break down beta glucose, so cellulose is a source of indigestible fibre
44
Q

what are the properties of lipids

A
  • non-polar
  • insoluble in water (hydrophobic)
45
Q

what is the structure of a triglyceride

A

one glycerol and three fatty acids
- glycerol is an alcohol, made of 3 carbons each with an OH and H group attached (C3H8O3)
- fatty acids are carboxylic acids (COOH) with a double bond to an Oxygen, they can be 2-24 carbons long
- they bond to form an ester linkage between the OH groups (COO with a double bond to one Oxygen)
- 3 H2Os are released in condensation

46
Q

what are the uses of triglycerides

A
  • energy source (release energy and generate ATP x2 carbohydrates, as energy is stored between hydrogen-carbon bonds, which there are many of
  • energy store (hydrophobic so dont cause osmotic uptake, so can be stored as insoluble energy
  • release of metabolic water (when respired, the hydrogen bonds are oxidised, useful for desert organisms e.g. desert kangaroo rats, camels, cacti)
  • insulation (myelin sheath, blubber)
  • buoyant (low density, whales floating for air)
  • shock absorber for organs and leaves
47
Q

what is the difference between saturated and unsaturated fatty acids

A
  • all fatty acid chains vary in length of R group (no. of carbons)
  • however the R group can either contain a double bond or not (unsaturated or saturated)
  • if the R group contains several double bonds, it is a poly-unsaturated fatty acid, if it only contains 1, its a mono-unsaturated fatty acid
  • if the H are on the same side of the plane of both double-bonded carbons, they are cis-fatty acids, and can be metabolised by enzymes
  • if they are on opposite sides, they are trans-fatty acids and cannot form enzyme- substrate complexes, and can’t be metabolised (trans-fat is linked to CHD)
  • unsaturated fatty acids are found as liquids at room temperature due to kink, saturated are solids
48
Q

what is the structure of a phospholipid

A
  • the head is made of a phosphate ion (PO4 with a 3- charge) and a glycerol molecule and is hydrophilic
  • the tails are either made of saturated or unsaturated fatty acids and are hydrophobic, unsaturated fatty acids have a kink in them
  • they are thus amphipathic, as they have both a hydrophobic and hydrophilic side
  • the fatty acids form ester linkages with the glycerol molecule
  • they are macromolecules
  • 3 H2Os are released in condensation
49
Q

what is the structure of cholesterol

A
  • 4 carbon-rings
  • hydrophilic OH end
  • hydrophobic hydrocarbon chain end
50
Q
A

biology A-level (3 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions