CH3: Biological Molecules Flashcards
1
Q
What are organic compounds?
A
compounds that contain both CARBON and HYDROGEN that are found in LIVING ORGANISMS.
2
Q
Examples of organic compounds:
A
- carbohydrates
- lipids
- proteins
- nucleic acids
3
Q
Exceptions that contain hydrogen and carbon but are inorganic compounds.
A
- Hydrogen carbonate (HCO⁻ ₃)
- Carbonates (CO₃²⁻)
- Oxides of carbon (CO, CO₂)
4
Q
All organic compounds are?
A
macromolecules
5
Q
What are the 2 types of macromolecules?
A
- Polymers
- Non-polymers
6
Q
What are polymers?
A
Organic compounds that are built from repeating basic units called MONOMERS.
7
Q
Which organic compounds are polymers?
A
- Complex carbohydrates
- Proteins
- Nucleic acid
8
Q
Which organic compound is a non-polymer?
A
Lipids
9
Q
Define what a condensation reaction is.
A
- Reaction
- bonds are created
- to join 2 or more simple compounds to form a complex compound
- with the REMOVAL of water
10
Q
Define what hydrolysis is.
A
- Bonds are broken
- to split up a complex complex biological molecule into its components
- with the ADDITION of water molecules.
11
Q
Both hydrolysis and condensation require…
A
enzymes
12
Q
What are carbohydrates?
A
- an organic compound
- made of CARBON, HYDROGEN and OXYGEN elements
- hydrogen and oxygen atoms are present in the ratio of 2:1.
13
Q
Types of carbohydrates:
A
- Sugars (simple and double sugars)
- Complex carbohydrates
14
Q
Sugars are (monomers/non-polymers/polymers)
A
monomers
15
Q
What are the properties of sugars?
A
- soluble in water > exerts osmotic pressure
- sweet to taste
16
Q
single sugars are known as…
A
monosaccharides
17
Q
double sugars are known as…
A
disaccharides
18
Q
What is the general formula of monosaccharides?
A
(CH₂O)n
19
Q
What is the general formula of disaccharides?
A
C₁₂H₂₂O₁₁
20
Q
Examples of monosaccharides:
A
Glucose, fructose, galactose, ribose
21
Q
Examples of disaccharides:
A
Sucrose (glu +fru)
Maltose (glu + glu)
Lactose (glu + gal)
22
Q
Glucose is commonly found in…
A
plants and animals
23
Q
Fructose is commonly found in…
A
plants
24
Q
Glucose can be represented by…
A
a hexagon (6 sides)
25
Fructose can be represented by...
a pentagon (5 sides)
26
Properties and functions of glucose:
1. SOLUBLE IN WATER
have hydroxyl group (OH-) that form hydrogen bonds >
(a) easily transportable in aqueous biological fluids (blood and sap)
(b) facilitates movement across cellular environments, enabling glucose to serve as a universal energy source
2. TRANSPORTABLE > shape
enhanced by facilitated diffusion > move across plasma/cell membrane efficiently
3. CHEMICALLY STABLE under physiological conditions > reduces likelihood of undesirable reactions during storage and transport
27
How to test for reducing sugars/simple sugars?
Benedict's test:
1. place an equal volume of food sample and Benedict's solution into a test tune
2. shake mixture and place in boiling water bath
3. in the presence of reducing sugar a precipitate will form and the blue solution will turn red
28
Properties of complex carbohydrates:
- Insoluble in water > does not exert osmotic pressure
- Does not taste sweet
29
Complex carbohydrates are known as...
Polysaccharides
30
What is the general formula for complex carbohydrates?
Cx(H₂O)y
31
Examples of complex carbohydrates:
Starch
Glycogen
Cellulose
32
The bond between sugars are known as?
Glycosidic bond
33
What is the structure of starch?
Made of thousands of glucose molecules joined together with glycosidic bonds.
34
Where is starch found?
What is the role of starch?
Found in storage organs of plants
1. stores carbohydrates in plants
2. broken down into glucose to provide energy for cell activities
35
What is the structure of cellulose?
Made form many glucose molecules that are ALTERNATIVELY INVERTED and joined together through glycosidic bonds.
36
Where is cellulose found?
What is the role of cellulose?
Found in cell wall of plants
Makes cell wall inflexible, protecting cell from undergoing LYSIS and mechanical DAMAGE.
37
Can humans digest cellulose?
No. Hence, cellulose is served as dietary fibre that prevents constipation.
38
What is the structure of glycogen?
BRANCHED molecule made of many glucose molecules joined together by glycosidic bonds.
39
Where is glycogen found?
What is the role of glycogen?
Stored in the liver and muscles in mammals
1. Stores carbohydrates
2. Digested to glucose to provide energy for cell activities
40
Why are glycogen and starch suitable as storage materials?
1. **Insoluble in water** > do not affect WP in cell
2. **Too large to diffuse through the cell membranes** > stay in the cell
3. Have **compact shapes which occupy less space** than all the individual glucose molecules that make up glycogen or starch molecule
4. Can be **easily hydrolysed** to glucose
41
Describe the process of hydrolysis of starch into glucose.
1. Starch is broken down into maltose molecules by amylase
2. Maltose molecules are broken down into glucose by maltase
42
What are the functions of carbohydrates?
- Glucose > needed as a substrate for respiration, to release energy for all cell activities
- Ribose > used for the formation of nucleic acids
- forms lubricants (e.g. mucus > carbs + proteins)
- forms nectar in flowers
- Cellulose > form supporting structures (e.g. cell wall)
43
How to test for starch?
Iodine test
1. add a few drops of iodine to food sample
2. iodine solution will turn from brown to blue-black in the presence of starch
44
What are lipids?
- Organic compounds
- containing carbon, hydrogen and oxygen
- with much lesser oxygen as compared to carbon and hydrogen.
45
Are lipids hydrophilic or hydrophobic?
Hydrophobic. However, they are soluble in organic solvents such as alcohol and acetone.
46
How are lipids classified?
1. Simple lipids (wax + triglycerides)
2. Compound lipids (glycolipids + phospholipids + lipoprotein)
3. Derived lipids (steroids)
47
Chemical composition of triglyceride molecule:
3 fatty acids + 1 glycerol
(= 1 triglyceride + 3 water)
48
What is a fatty acid made of?
carboxylic acid (COOH) + hydrocarbon chain
49
Hydrocarbon chain can be either _______ or ______.
unsaturated - contain one or more carbon-carbon double bonds C=C
OR
saturated - lack carbon carbon double bonds
50
Chemical formula for glycerol:
C₃H₈O₃
51
Outline how triglyceride is formed:
- Condensation reaction takes place
- Ester bonds are formed between 3 molecules of fatty acids and 1 molecule of glycerol
- 3 molecules of water are removed
52
Which enzyme is required for the hydrolysis of triglycerides?
Lipase
53
Properties of triglycerides as oils:
- have unsaturated fatty acids
- presence of at least 1 carbon-carbon double bond
- have relatively short fatty acid chains
- lower melting point and molecular weight
- insoluble in water
54
Properties of triglycerides as fats:
- have saturated fatty acids
- absence of carbon-carbon double bond
- higher melting point and molecular weight
- insoluble in water
55
Functions of fats:
Triglycerides:
1. source of LONG TERM storage of energy
triglycerides have a higher energy value compared to carbs as it contains a greater number of carbon-hydrogen bond per gram
2. Heat insulator
3. Buoyancy in aquatic animals
adipose cells (specialised fat cells) group tgt to from adipose tissue that form blubber
4. Solvent for fat-soluble vitamins (A,D,E and K) and other substances (e.g. hormones)
5. Provides metabolic water
Oxidation of triglycerides during respiration produces metabolic water
Phospholipids: major component of biological membranes
7. Reduce water loss from the skin surface
(a) oily substance forms a thin layer over the skin surface > reduces rate of evaporation of water
(b) reduces rate of heat loss from the skin
56
How to test for fats?
Ethanol emulsion test
1. add equal volume of ethanol and water
2. shake mixture
3. a white emulsion is formed when ethanol and water are added to fats.
57
What are proteins?
- Organic compounds
- made from elements carbon, hydrogen, oxygen and nitrogen
- sulfur may also be present
58
Where are proteins found in the body?
- membrane proteins
- enzymes
- antibodies
- hormones
59
Structural formula of amino acid:
Central carbon formula covalently bonded to 4 groups:
1. ≥1 amino group (-NH2)
2. a carboxyl group (-COOH)
3. a hydrogen atom
4. a R group/side chain
60
Differentiate between essential and non-essential amino acids
Essential: AA that cannot be synthesised by the human body due to the lack of specific enzymes > must be consumed in diet
Non-essential: can be synthesised by the human body through metabolic processes > don't need to be consumed in diet
61
Describe the process of amino acids forming polypeptide:
Through condensation reaction with the removal of water.
H is lost from the amino group and OH is lost from the carboxyl group
Peptide bond between C and N is formed
62
How do polypeptide chains form proteins?
one or more polypeptide chains FOLD into a THREE-DIMENSIONAL conformation as a result of 4 other type of bonds:
1. disulfide bonds
2. ionic bonds
3. hydrogen bonds
4. hydrophobic interactions
63
Why must polypeptide chains be folded?
Amino acids in polypeptide chains are only functional when it is folded to form a 3D conformation.
64
What is denaturation?
**Loss of the three-dimensional conformation** of a protein molecule as the **weak bonds** in the proteins are **broken** and the polypeptide chain(s) **unfold(s)**
65
Examples of agents that may cause denaturation:
1. Temperature
high k.e supplied to protein
> atoms in proteins vibrate violently
> disrupts hydrogen bonds, ionic bonds and hydrophobic interactions which help to maintain the 3D conformation
> protein coagulates
2. Extreme pH
additional H+ ions in acids can combine with COO- groups of AA to form COOH
> ionic bonds break
66
Functions of proteins:
1. used in cell synthesis, repair and growth
2. forms antibodies to combat diseases
3. forms transport (e.g. haemoglobin, membrane proteins) and structural proteins (e.g. collagen, keratin)
4. synthesis enzymes that speed up chemical reactions
5. synthesises hormones (e.g. insulin) to stimulate organs to perform specific functions
67
How to test for proteins?
Biuret's test
1. Add equal volume of food sample and biuret solution
2. shake
3. mixture will turn from blue to violet in the presence of proteins
