1.1 (1) - Biological Molecules Flashcards
Introduction to biological molecules Carbohydrates and monosaccharides Carbohydrates - disaccharides and polysaccharides Starch, glycogen and cellulose Lipids Proteins Enzyme action Enzyme inhibition
1
Q
What is a monomer?
A
1 single unit of a polymer
2
Q
What is a polymer?
A
A chain of monomers, making a larger molecule
3
Q
What is the function of carbohydrates?
A
- Commonly used as respiratory substrates
- Structural components in plasma membranes and cell walls
4
Q
What is the function of lipids?
A
- Insulation
- Energy source
- Help create cell membranes
5
Q
What is the function of proteins?
A
Form many cell structures
6
Q
What is the function of nucleic acid?
A
Used for production to make genetic material
7
Q
What is a respiratory substrate?
A
A molecule that can release energy to produce ATP in a cell
8
Q
What kind of sugar is a monosaccharide?
A
Hexose sugar
9
Q
What is the difference between an ɑ-glucose and a β-glucose?
A
ɑ-glucoses have their hydroxyl below Carbon 1
β-glucoses have their hydroxyl above Carbon 1
10
Q
What kind of reaction are monosaccharides formed during?
A
Condensation reaction
11
Q
What bond are 2 monosaccharides joined together in a disaccharide by?
A
Glycosidic bond (covalent)
12
Q
What is a carbohydrate monomer called?
A
Monosaccharide
13
Q
What are the 3 main monosaccharides?
A
- Glucose
- Fructose
- Galactose
14
Q
What are 2 monosaccharides joined together called?
A
Disaccharides
15
Q
What are the 3 main disaccharides?
A
- Maltose
- Sucrose
- Lactose
16
Q
What 2 monosaccharides make up maltose?
A
2 ɑ-glucoses
17
Q
What 2 monosaccharides make up sucrose?
A
1 glucose and 1 fructose
18
Q
What 2 monosaccharides make up lactose?
A
1 glucose and 1 galactose
19
Q
What are many monosaccharides joined together called?
A
Polysaccharides
20
Q
What are the 3 main polysaccharides?
A
- Cellulose
- Glycogen
- Starch
21
Q
What monosaccharides is cellulose made up of?
A
Chains of β-glucoses
22
Q
What monosaccharides is glycogen made up of?
A
Chains of ɑ-glucoses
23
Q
What monosaccharides is starch made up of?
A
Chains of ɑ-glucoses
24
Q
What is a condensation reaction?
A
When two monosaccharides join and a water molecule is removed
25
What is a hydrolysis reaction?
When water is added to a disaccharide to break the glycosidic bond between the 2 monosaccharides
26
What is a reducing sugar?
One that can donate electrons to another chemical
27
Describe the Benedict's Test
1) Add 2cm3 of food sample to a test tube in a paste / liquid form
2) Add 2cm3 of Benedict's reagent
3) Heat the mixture gently over a water bath for 5 minutes
28
What are the test results (colours) for the Benedict's Test?
```
Blue - None present
Green - Trace
Yellow - Low
Orange/red - Moderate
Maroon - High
```
29
Is the Benedict's Test quantitative or semi-quantitative?
Semi-quantitative
30
What is a semi-quantitative test?
It doesn't measure the precise quantity of a substance, BUT the result expresses an estimate of how much of a detected substance is present (eg. colour spectrum)
31
What is the test for non-reducing sugars?
1) Make sure the food sample is liquid
2) Add 2cm3 of food sample to 2cm3 of Benedict's reagent in a test tube → filter
3) Place test tube in water bath for 5 minutes. If the colour does NOT change, reducing sugars are NOT present
4) In a new test tube, add 2cm3 of food sample to 2cm3 dilute hydrochloric acid (DHA) and put into a water bath for 5 minutes. The DHA will hydrolyse any NON-REDUCING disaccharides present into its REDUCING monosaccharides
5) Slowly add some sodium hydrogen carbonate solution to the test tube (neutralising it). Test with pH paper, the solution should be alkaline
6) Re-test the resulting solution by heating it with 2cm3 Benedict's reagent in a water bath for 5 minutes
7) If a non-reducing sugar was present in the original sample, the reagent will now turn brown-orange, because of the reducing sugars that were produced from the hydrolysis of the non-reducing sugars
32
Describe starch
- Plant energy-storage molecule
- It makes it insoluble, so that they don't draw water into the cell and affect water potential
- Doesn't dissolve, so there is no effect on osmotic potential, it won't diffuse
- It can be hydrolysed to ɑ-glucoses, which is easy to transport and good for respiration
- It can take a more-branched structure which has more ends, speeds up its break down
- Forms close spiral structures - allows it to be tightly packed
33
Describe glycogen
- Found in animals
- Insoluble
- Function - energy storage and release molecule
- Forms a many-branched structure, so that there are lots of ends for glucose to be released from
34
Describe cellulose
- Structural carbohydrate
- β-glucoses are ALTERNATING (flipped over), forming really strong chains
- Dietary fibre
35
What three chemical elements are lipids composed of?
Carbon (C), hydrogen (H) and oxygen (O)
36
Do lipids have a lower or higher proportion of oxygen to carbon and hydrogen than carbohydrates?
Lower proportion
37
What substances are lipids soluble / insoluble in?
Soluble - organic substances (eg. alcohol and acetone)
| Insoluble - water
38
What are 4 functions of lipids?
- Energy storage molecule
- Waterproofing
- Insulation
- Physical protection
39
If it is solid between 10°C and 20°C, the lipid is a...
Fat
40
If it is liquid between 10°C and 20°C, the lipid is an...
Oil
41
What is the structure of a triglyceride?
3 fatty acids with a glycerol molecule joined via an ester bond
42
What is the main cause of fatty acid variation?
Saturation
43
How many double bonds does a monounsaturated fatty acid have?
1 double bond
44
How many double bonds does a saturated fatty acid have?
0 double bonds
45
How many double bonds does a polyunsaturated fatty acid have?
More than 1 double bond
46
How is a phospholipid different to a triglyceride?
One of the fatty acids is replace with a hydrophilic phosphate molecule
47
What do phospholipid bilayers help to make?
Cell membrane
48
What is the significance of phospholipids being polar?
They can form bilayers in aqueous solutions, forming a barrier between the intercellular and extracellular fluid
49
Phospholipid structure aids with the formation of...
Glycolipids
50
Describe the emulsion test for lipids
1) Take a clean, dry test tube
2) Add 5cm3 ethanol to 2cm3 of food sample
3) Shake the tube thoroughly to dissolve any lipid in the sample
4) Add 5cm3 water, shake gently
5) A cloudy-white emulsion indicates the presence of a lipid
6) As a control, repeat the procedure using water instead of the food sample; the control should remain clear
51
What are the monomers of proteins called?
Amino acids
52
What is the generic structure of a protein?
- Central ɑ-carbon
- Amino group (left - H-N-H)
- Solitary hydrogen (above)
- Carboxyl group (right - OH-C=O)
- R-group (varies the protein)
53
How many types of amino acids are proteins made of?
All 20 amino acids
54
What is the name of a polymer of amino acids joining together?
Polypeptide
55
What is the joining of many monomers to make a polymer called?
Polymerisation
56
What bond are amino acids joined by?
Peptide bond
57
What molecule is formed between the -OH from the carboxyl group when 2 amino acids join?
Water molecule
58
Describe a protein's primary structure
- A chain of amino acids
- It is determined by the type, sequence and number of amino acids
- It determines the shape, structure and function of the protein because of the r-group and different molecular structure
59
Describe a protein's secondary structure
- Occurs as H bonds form between the +charged H of the -NH and the -charged oxygen of the -C=O group
- The H bonds tend to be weak, but they are strong enough to twist the polypeptide chain into a 3D shape (ɑ helix OR β-pleated sheet)
60
Describe a protein's teritary structure
- It is determined by the primary structure
- It's the result of further twisting of the secondary structure
- Plays a significant role in determining the protein's behaviour
- Maintained by:
- Disulfide bonds
- Hydrogen bonds
- Ionic bonds
61
Describe a protein's quaternary structure
- Consists of 2 or more polypeptide chains bonded together
- Some large proteins also include a non-peptide part, called a prosthetic group (eg. inorganic iron ions are the prosthetic group in haemoglobin)
62
What 5 factors affect the rate of enzyme-controlled reactions?
- Enzyme concentration
- Substrate concentration
- Concentration of competitive and non-competitive inhibitors
- Temperature
- pH
63
What 3 things are needed for chemical reactions to occur naturally?
- Reactants must collide with enough energy to change their atom arrangement
- The free energy of the products must be less than that of the reactants (substrates)
- There must be enough activation energy
64
What kind of protein is an enzyme?
Globular protein
65
What is the shape of an enzyme's active site detemined by?
The protein's tertiary structure
66
What is a protein's primary structure determined by?
- Which amino acids are present
- How many are present
- What order they're arranged in
67
In the Induced Fit Model (IFM), how to enzymes, substrates and active sites fit together?
- The active site of an enzyme only takes the shape of the substrate when they collide
- The flexibility of the polypeptide chains in the enzyme allows it to change the shape of its active site around the substrate, if all the right bonds can be formed in all the right places
- If this happens, the reaction can happen
68
How is the enzyme able to shape its active site around a substrate?
The flexibility of the polypeptide chains allows the active site to shape the substrate, only if all the right bonds can be formed in all the right places
69
What is the molecule called that forms between an enzyme and a substrate when they bond?
Enzyme-substrate complex
70
How does temperature affect the rate of enzyme-catalysed reactions?
If the temperature is increased, the active site starts to denature, so the enzyme can't fit withe the substrate, so it can't catalyse the reaction
71
How does pH affect the rate of enzyme-catalysed reactions?
- The hydrogen and ionic bonds (in the enzyme) will be disrupted by the presence of H+ or OH- ions
- If the ionic bonds are swamped with H+ or OH- ions, the electrostatic forces of attraction will be interfered with and they'll weaken
- Changes in pH away from the enzyme's optimum pH will interfere with the hydrogen and ionic bonds in the enzyme's tertiary structure
- The shape changes and the active site no longer matches the substrate, so the enzyme can't react with it
72
What does a higher concentration of substrates mean for the reaction?
Means that it's more likely for a substrate to bind with an active site
73
What does 'inhibition' mean?
Certain "inhibitor molecules" can prevent an enzyme from working
74
What are the 2 types of enzyme inhibition?
- Competitive inhibition
| - Non-competitive inhibition
75
Describe competitive inhibition
When a molecule, other than an enzyme-specific substrate, is complementary to the active site of the enzyme and stops the reaction from being catalysed
76
Describe non-competitive inhibition
- Doesn't occupy the active site
- They attack the allosteric site, distorting the shape of the active site so that it's not longer complementary to the substrate
77
Describe how inhibitors affect enzymes
- Competitive inhibitor mimics substrate and competes for the active site
- Non-competitive inhibitor alters conformation of enzyme so active site is no longer fully functioning
78
Which type of lipid is a good energy-storage molecule? Why?
Triglyceride - there is a higher ratio of carbon-hydrogen bonds to oxygen bonds
