CH3: Biological Molecules Flashcards
(69 cards)
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 macromolecules?
A
A large molecule comprised of thousands of covalently bonded atoms
6
Q
What are the 2 types of macromolecules?
A
- Polymers
- Non-polymers
7
Q
What are polymers?
A
Organic compounds that are built from repeating basic units called MONOMERS.
8
Q
Which organic compounds are polymers?
A
- Carbohydrates
- Proteins
- Nucleic acid
9
Q
Which organic compound is a non-polymer?
A
Lipids
10
Q
Define what a condensation reaction is.
A
- Enzyme are needed
- create bonds
- to join 2 or more simple molecules to form a complex compound
- with the REMOVAL of water
11
Q
Define what hydrolysis is.
A
- Enzymes are needed
- Break bonds
- Split up a complex complex biological molecule into its components
- with the ADDITION of water molecules.
12
Q
Both hydrolysis and condensation require…
A
enzymes
13
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.
14
Q
Types of carbohydrates:
A
- Sugars (simple and double sugars)
- Complex carbohydrates
15
Q
sugars are (monomers/non-polymers/polymers)
A
monomers
16
Q
What are the properties of sugars?
A
- soluble in water > exerts osmotic pressure
- sweet to taste
17
Q
single sugars are known as…
A
monosaccharides
18
Q
double sugars are known as…
A
disaccharides
19
Q
What is the general formula of monosaccharides?
A
(CH₂O)n
20
Q
What is the general formula of disaccharides?
A
C₁₂H₂₂O₁₁
21
Q
Examples of monosaccharides:
A
Glucose, fructose, galactose, ribose
22
Q
Examples of disaccharides:
A
Sucrose (glu +fru)
Maltose (glu + glu)
Lactose (glu + gal)
23
Q
Glucose is commonly found in…
A
plants and animals
24
Q
Fructose is commonly found in…
A
plants
25
Glucose can be represented by...
a hexagon (6 sides)
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Fructose can be represented by...
a pentagon (5 sides)
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Properties of glucose:
1. SOLUBLE in water > easily transportable
have hydroxyl group (OH-) that readily from hydrogen bonds
(a) easily transportable in Aq biological fluids (blood and sap)
(b) enables it to move across cellular environments (plasma membrane through facilitated diffusion) > serve as a universal energy source
2. CHEMICALLY STABLE under physiological conditions > reduces likelihood of undesirable reactions during storage and transport
28
Which sugars are reducing sugars?
- all single sugars
- lactose
29
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
30
Properties of complex carbohydrates:
- Insoluble in water > does not exert osmotic pressure
- Does not taste sweet
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Complex carbohydrates are known as...
Polysaccharides
32
What is the general formula for complex carbohydrates?
Cx(H₂O)y
33
Examples of complex carbohydrates:
Starch
Glycogen
Cellulose
34
The bond between sugars are known as?
Glycosidic bond
35
What is the structure of starch?
Made of thousands of glucose molecules joined together with glycosidic bonds.
36
Where is starch found?
What is the role of starch?
Found in storage organs of plants (leaves. stems, roots, seeds, fruits)
1. stores carbohydrates in plants
2. broken down into glucose to provide energy for cell activities
37
What is the structure of cellulose?
Made form many glucose molecules that are ALTERNATELY INVERTED and joined together through glycosidic bonds.
38
Where is cellulose found?
What is the role of cellulose?
Found in cell wall of plant cells
Makes cell wall inflexible, protecting cell from undergoing LYSIS and mechanical DAMAGE.
cannot be digested by humans > serves as dietary fibre to prevent constipation in humans
39
Can humans digest cellulose?
No. Hence, cellulose is served as dietary fibre that prevents constipation.
40
What is the structure of glycogen?
BRANCHED molecule made of many glucose molecules joined together by glycosidic bonds.
41
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
42
Why are glycogen and starch suitable as storage materials in cells?
1. **Insoluble in water** > do not exert osmotic pressure + affect WP in cell
2. **Too large to diffuse through the plasma membrane** > won't be easily lost from 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
43
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
44
What are the functions of carbohydrates?
- Glucose
> needed as a substrate for respiration, to release energy for all cell activities
> through pathways such as glycolysis and cellular respiration, the complete oxidation of a goucose molecule generates substantial amts of ATP, making it an indispensable substrate for sustaining cellular functions
- 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)
- can be converted other organic compounds such as amino acids
45
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
46
What are lipids?
- Organic compounds
- containing carbon, hydrogen and oxygen
- with much lesser oxygen as compared to carbon and hydrogen.
47
Are lipids soluble in water or organic solvents?
Lipids are hydrophobic. They are soluble in organic solvents such as alcohol and acetone.
48
How are lipids classified?
1. Simple lipids (wax + triglycerides)
2. Compound lipids (glycolipids + phospholipids + lipoprotein)
3. Derived lipids (steroids)
49
Chemical composition of triglyceride molecule:
3 fatty acids + 1 glycerol
(= 1 triglyceride + 3 water)
50
What is a fatty acid made of?
carboxylic acid (COOH) + hydrocarbon chain
51
Hydrocarbon chain can be either _______ or ______.
unsaturated - contain one or more carbon-carbon double bonds C=C
OR
saturated - lack carbon carbon double bonds
52
Chemical formula for glycerol:
C₃H₈O₃
53
Outline how triglyceride is formed:
- Condensation reaction takes place
- 1 water molecule forms an ESTER bond with each fatty acid molecule
- ESTER bonds are formed between 3 molecules of fatty acids and 1 molecule of glycerol
- 3 molecules of water are removed
54
Outline how triglycerides are broken down
Through hydrolysis
1 triglyceride molecule is broken down by LIPASE to form 1 glycerol and 3 fatty acid molecules with the addition of water
55
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
56
Properties of triglycerides as fats:
- have saturated fatty acids > absence of carbon-carbon double bond
- higher melting point and molecular weight
- insoluble in water
57
Functions of fats: (triglycerides + phospholipids)
Triglycerides:
1. source of LONG TERM energy storage
> yields twice as much energy as carbs
> greater no. of carbon-hydrogen bond per gram
2. Heat insulator + buoyancy in aquatic animals
> adipose cells (specialised fat cells) group tgt to from adipose tissue that form blubber
3. Solvent for fat-soluble vitamins (A,D,E and K) and other substances (e.g. hormones)
4. Provides metabolic water
> Oxidation of triglycerides during respiration produces metabolic water
Phospholipids:
5. Form biological membranes
6. Reduce water loss from the skin surface
> glands in skin secrete oily substance that forms a thin layer over the skin surface
> reduces rate of evaporation of water + heat loss from the skin
58
How to test for fats?
Ethanol emulsion test
1. add equal volume of ETHANOL and WATER to food sample
2. shake mixture
3. a white emulsion is formed when ethanol and water are added to fats.
59
What are proteins?
- Organic compounds
- made from elements carbon, hydrogen, oxygen and nitrogen
- sulfur may also be present
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Where are proteins found in the body?
- membrane proteins
- enzymes
- antibodies
- hormones
61
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
62
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
63
Describe the process of amino acids forming polypeptide:
Through condensation reaction.
H is lost from the amino group and OH is lost from the carboxyl group
PEPTIDE bond between C and N is formed
64
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
65
Why must polypeptide chains be folded?
Amino acids in polypeptide chains are only functional when it is folded to form a 3D conformation.
66
What is denaturation?
- **Loss of the 3D conformation** of any soluble protein molecule
- as the **weak bonds** in the proteins are **broken**
- and the polypeptide chain(s) **unfold(s)**
- because of heat or chemicals such as acids and alkalis
67
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 carboxyl (COO-) groups of AA to form carboxylic acid (COOH)
> ionic bonds break
68
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
69
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
