Biological Molecules Flashcards
(39 cards)
1
Q
What is covalent bonding?
A
Atoms sharing a pair of electrons in their outer shells, forming a molecule
2
Q
What is ionic bonding?
A
When ions with opposite charges are electrostatically attracted, these bonds are weaker than covalent bonds
3
Q
What is hydrogen bonding?
A
- When one of the atoms is more electronegative than the other, the electrons will be closer to that atom, making it slightly negative ans the other atom slightly positive
- The uneven distribution makes the molecule polar, the negative region of one molecule and the positive region of another attract each other, forming a weak electrostatic bond
4
Q
What are polymers and how are they formed?
A
They are long chains of monomers that are formed in condensation reactions, where a molecule of water is produced
5
Q
What is hydrolysis?
A
The addition of water to break bonds, splitting a polymer into its constituent monomers
6
Q
What is metabolism?
A
All the chemical processes that take place in living organisms
7
Q
What is a molar solution?
A
A solution that contains one mole of a solute in each litre of solution
8
Q
What are monosaccharides?
A
Sweet tasting, soluble, monomers of carbohydrates
9
Q
What is the test for reducing sugars?
A
- Grind up food sample in water and add to a test tube
- Add an equal volume of Benedict’s reagent
- Heat the mixture gently in a water bath for five minutes
- If reducing sugar is present, the sample will turn from blue to orange-brown
10
Q
What are disaccharides?
A
Monosaccharides that are joined together by a glycosidic bond during a condensation reaction
11
Q
What are the examples of disaccharides?
A
- Glucose and glucose to form maltose
- Glucose and fructose to form sucrose
- Glucose and galactose to form lactose
12
Q
What is the test for non-reducing sugars?
A
- Grind up food sample in water and add to test tube
- Add equal volume of Benedict’s reagent
- Heat sample gently in a water bath for five minutes
- If sample does not change colour, them a reducing sugar is not present
- Add new food sample to equal volume hydrochloric acid and place in water bath for five minutes
- Slowly add sodium hydrogencarbonate to neutralise the acid
- Re-do the reducing sugar test, if sample now changes colour this means the non-reducing sugars have been hydrolysed into reducing sugars
13
Q
What is starch?
A
- A polysaccharide that is found in many parts of plants
- It is formed by the joining alpha glucose molecules by glycosidic bonds in a series of condensation reactions
14
Q
What is the test for starch?
A
- Add sample to test tube
- Add a few drops of iodine in potassium iodide to the sample
- Solution changes from orange to blue-black if starch is present due to the iodine being reduced
15
Q
How is starch’s structure suitable for energy storage?
A
- Insoluble so doesn’t affect water potential
- Large so doesn’t diffuse out of cells
- Compact, so a lot of it can be stored in a small space
- Can be hydrolysed into alpha glucose which can be used in respiration
- Highly branched for rapid enzyme action if glucose needs to be released for respiration
16
Q
How is glycogen’s structure suitable for storage?
A
- Insoluble so doesn’t draw water into the cells via osmosis
- Insoluble so doesn’t diffuse out of cells
- Compact so a lot of it can be stored in a small space
- More branched than starch so can more rapidly be broken down into glucose for respiration
17
Q
How is cellulose’s structure suitable for providing rigidity and support?
A
- Made of straight, unbranched chains of beta glucose
- Chains run parallel to each other and are cross linked by hydrogen bonds which adds collective strength
- Chains are grouped to form microfibrils which group to form fibres to provide more strength
18
Q
What are characteristics of lipids?
A
- Insoluble in water
- Soluble in organic solvents
- Contain carbon, hydrogen and oxygen
19
Q
What are the two main groups of lipids?
A
- Triglycerides
- Phospholipids
20
Q
What are the roles of lipids?
A
- Make up cell membranes
- Source of energy when oxidised
- Waterproofing as they are insoluble in water
- Insulation as they are slow conductors of heat
- Protection of delicate organs
21
Q
What are triglycerides?
A
- Three fatty acids joined to glycerol by an ester bond
- They are non-polar
- When saturated, meaning they have no double carbon bonds, they are solid at room temperature
- When unsaturated, meaning they have atleast one double carbon bond, they are liquid at room temperature ( oils )
22
Q
What are phospholipids?
A
- Two fatty acids, a phosphate group and a glycerol joined by an ester bond
- They are polar molecules
- The fatty acids are the hydrophobic tail
- The phosphate group is the hydrophilic head
23
Q
How are phospholipids used in the cell membrane?
A
- They form a bilayer
- The hydrophobic tails point inwards, the hydrophobic heads point outwards
24
Q
What is the test for lipids?
A
- Add sample to test tube with ethanol
- Shake tube thoroughly to dissolve any lipid in the sample
- Add water and shake gently
- A cloudy-white emulsion indicates the presence of a lipid
25
What are amino acids?
The monomer unit used to create a polypeptide
26
What four chemical groups are attached to the central carbon atom of an amino acid?
- Amino group ( —NH2 )
- Carboyxl group ( —COOH )
- Hydrogen atom ( —H )
- R group, which can be a variety of different chemical groups
27
How are peptide bonds formed?
- During a condensation reaction
- The —OH from the carboxyl group of one amino acid and the —H of another amino acid join to make a water molecule
- The peptide bond is formed between the carbon atom of one amino acid and the nitrogen atom of the other
28
What is the primary structure of a protein?
The sequence of amino acids in a polypeptide chain
29
What is the secondary structure of a protein?
- Hydrogen bonds between the positive —NH group and the negative —C=O group
- Causing the polypeptide chain to twist into a 3D shape called an alpha helix
30
What is the tertiary structure of a protein?
- Specific structure formed from the twisting and folding of alpha helixes
- This structure is held by disulphide bridges, ionic bonds, and hydrogen bonds
31
What is the quaternary structure of proteins?
How the polypeptide chains are linked together to form the large protein complex
32
What is the test for proteins?
1. Add sample in test tube
2. Add equal volume of sodium hydroxide
3. Add a few drops of dilute copper (II) sulfate solution and mix gently
4. Solution will go from blue to lilac if protein is present
33
What are enzymes?
- Globular proteins that act as catalysts
- They provide an alternative reaction pathway with a lower activation energy
34
What is the induced fit model of enzyme action?
- Enzyme active site changes slightly when in contact with a substrate forming an enzyme-substrate complex
- As the enzyme changes its shape, it puts a strain on the substrate molecule
- The strain distorts the bonds in the substrate and so lowers the activation energy required to break the bonds
35
What is required for enzymes to work?
- Enzyme to have an active site that fits the substrate
- Enzyme must come into contact with the substrate
36
What effect does temperature have on enzyme action?
- Increase in temperature increases kinetic energy of molecules, meaning there are more frequent collisions. This creates more enzyme-substrate complexes and so rate of reaction increases
- Too high of a temperature denatures the enzyme which permanently changes its shape, making the enzyme unable to function
37
What effect does pH have on enzyme action?
- Change in pH alters the charge on the amino acids that make up the active site of the enzyme, therefore substrate can no longer bind to it
- If change in pH is significant, the bonds holding the tertiary structure may break, changing the active site shape
38
What are competitive inhibitors?
- Molecules with similar shapes to substrates that occupy the active site of an enzyme
- Inhibitor is not permanently bound to the active site, so when it leaves, another molecule can take its place
39
What are non-competitive inhibitors?
- Molecules that attach themselves to the enzyme on an allosteric site
- This changes the shape of the enzyme’s active site, so the substrate can no longer occupy it and the enzyme can no longer function
