1
Q
What is the polarity of water? (4)
A
- water is an inorganic compound, consists of hydrogen & oxygen elements
- water molecules are polar molecules because shared electron between H & O will be attracted towards O2 which is more electronegative
- polarity produced hydrogen bonds & allows water to act as universal solvent
- allows solutes (glucose, electrolytes) to be transported through the plasma membrane into cells for biochemical reactions
2
Q
What is cohesive force & adhesive force of water? (3)
A
- water molecules are attached to each other through a cohesive force
- water molecules are also attached to other surfaces through adhesive force
- both forces produces the capillary action which allow water to enter & move along narrow spaces (xylem tube)
3
Q
What is the specific heat capacity of water? (3)
A
- high specific heat capacity: 4.2 kJ/kg degree Celsius
- 4.2 kJ of heat energy is required to raise the temperature of 1 kg of water by 1 degree Celsius
- water absorbs a lot of heat energy with a small rise of temperature, this characteristic is very important to maintain the body temperature of organisms
4
Q
What are organic compounds?
A
- chemical compounds that contain carbon elements
5
Q
What is macromolecules? (3)
A
- large & complex molecules
- most macromolecules are polymers comprising small molecules known as monomers (building blocks)
- carbohydrates, proteins & nucleic acids are polymer molecules of organic compounds
6
Q
What are the elements on carbohydrates (3), their ratio & chemical formula?
A
- carbon , r=1
- hydrogen, r=2
- oxygen, r=1
- chemical formula: (CH2O)n
7
Q
What are the types of carbohydrates? (3)
A
- monosaccharides (simple sugars)
- disaccharides
- polysaccharides (complex sugars)
8
Q
What are monosaccharides and their characteristics? (4)
A
- monosaccharides are carbohydrate monomers (simplest carbohydrate units)
- can combine to form polymers through condensation
- most taste sweet, can form crystals & dissolve in water
- has reducing power (able to transfer hydrogen/electron to other compounds)
9
Q
What are some examples of monosaccharides and their characteristics? (3)
A
- glucose (found in plants [rice/wheat] & fruits [grapes], most common monosaccharide & most polysaccharides are formed from this sugar)
- fructose ( found in honey & sweet fruits)
- galactose ( found in milk)
10
Q
What happens when monosaccharides are heated in Benedict’s solution? (2)
A
- when monosaccharides is heated in Benedict’s solution, the monosaccharide will reduce the blue copper (II) sulphate to brick red precipitate of copper (I) oxide (not soluble in water)
- all monosaccharides give this reaction (aka reducing sugars)
11
Q
What are disaccharides? Give 3 examples.
A
- molecules that are formed when 2 simple sugar molecules (monosaccharides) combine through condensation to form a disaccharide unit (involves removal of a water molecule)
- sucrose (non reducing sugar)
- maltose (reducing sugar)
- lactose (reducing sugar)
12
Q
How is disaccharides formed? (3 word equations)
A
glucose + glucose → maltose + water
glucose + fructose → sucrose + water
glucose + galactose → lactose + water
[→ symbolizes condensation]
13
Q
How can disaccharides be broken down to their monosaccharide units?
A
- through hydrolysis & addition of 1 water molecule
14
Q
What are the word equations for break down of disaccharides to their monosaccharide units? (3)
A
maltose + water → glucose + glucose
sucrose + water → glucose + fructose
lactose + water → glucose + galactose
[→ symbolizes hydrolysis]
15
Q
What are polysaccharides and their characteristics (5)?
A
- sugar polymers consisting monosaccharide monomers
- formed through condensation involving 100s of monosaccharides to form long molecular chains
- not soluble in water du to large molecular size
- not sweet, des not crystallize
- can disintegrate through hydrolysis with help of dilute acid, boiling & enzyme reaction
16
Q
State the importance of carbohydrate in cells (3)
A
- as source of energy (glucose)
- as food reserve (glycogen in animal cells, starch in plant cells)
- as a support structure ( cellulose in plant cell wall)
17
Q
What are proteins and its characteristics? (3)
A
- a complex compound composed of carbon, hydrogen, oxygen & nitrogen ( also contain sulphur & phosphorus)
- composed of 1/more polymers (polypeptides)
18
Q
What are polypeptides made up of? (2)
A
- 50 to 1000s of amino acid molecules
- amino acids are linked together through condensation
19
Q
What are dipeptides? (2)
A
- composed of 2 amino acid molecules which are linked together by a peptide bond through condensation process (1 water molecule is removed)
- further condensation can link more amino acids to form a polypeptide chain
20
Q
What is the word equation for amino acid to dipeptide and dipeptide broken down into amino acid? (2)
A
amino acid + amino acid → dipeptide + water [→ symbolises condensation]
dipeptide + water → amino acid + amino acid [→ symbolises hydrolysis]
21
Q
What is the importance of proteins/polypeptides in a cell? (6)
A
- build new cells
- repair damaged tissues
- synthesis of enzymes, hormones, antibodies & haemoglobin
- form building blocks (keratin in skin, collagen in bones, myosin in muscle tissues)
- breakdown of protein/polypeptides by digestive enzymes provides energy
- polypeptides can be disintegrated into amino acids which is used again to build the protein molecules needed by the body
22
Q
What are lipids and their characteristics? (3)
A
- naturally occurring hydrophobic compounds found in plant & animal tissues
- made up of C,H,O elements [ratio of hydrogen atom to oxygen atom is much higher]
- insoluble in water but soluble in other organic solvents [ alcohol, ether, chloroform]
23
Q
State the types of lipids. (4)
A
- fats
- waxes
- phospholipids
- steroids
24
Q
State the characteristics of fats. (2)
A
- fats & oils are triglycerides [ type of ester from the condensation of 1 glycerol molecule with 3 fatty acids molecules]
- triglycerides can be hydrolysed again into fatty acids & glycerol through hydrolysis
25
What is glycerol?
- type of 3 carbon alcohol that contain 3 hydroxyl groups (-OH)
26
What are the 2 types of fatty acids?
- saturated fat
| - unsaturated fat
27
What are the similarities between saturated fats and unsaturated fats? (3)
- consists of C,H,O elements
- contains glycerol & fatty acids
- contain nonpolar molecules
28
What are the differenced between saturated fats (4) and unsaturated fays (4)?
Saturated fats
- fatty acids have single bonds between carbon
- do not form chemical bonds with additional hydrogen atom because all bonds between carbon atoms are saturated
- solid in room temperature
- source: butter, animal fat
Unsaturated fats
- fatty acids have at least 1 double bond between carbon
- double bond can receive 1/more additional hydrogen atoms because carbon atoms are unsaturated
- liquid in room temperature
- source: olive, fish oil
29
What is the characteristic of wax? (2)
- contains 1 molecule of alcohol that combine with another molecule of fatty acid
- waterproof
30
What are phospholipids and what is it made up of? (2)
- major component of plasma membrane
| - made up of 1 glycerol molecule combine with 2 fatty acid molecules & 1 phosphate group
31
What are steroids (1) and their examples (4)?
- lipids that do not contain fatty acids
| - cholesterol, testosterone, estrogen, progesterone
32
What are the importance of lipids in cells [Fats] (3)?
Fats
- reserved energy for animals
- liner to protect internal organs
- heat insulator for animals
33
What are the importance of lipids in cells [Wax] (2)?
Wax
- important component in cuticles that cover the epidermis of leaves
- important component in sebum secreted by skin
34
What are the importance of lipids in cells [Glycolipid] (2) and [cholesterol] (1)?
```
Glycolipids
- ensure the stability of the plasma membrane
- help in cell identification process
Cholesterol
- important in steroid hormone synthesis
```
35
What are nucleic acids the elements that form them (5) & types (2)?
- nucleic acids are 1 or 2 polymer chains comprising of nucleotide monomers
- formed from carbon, hydrogen, oxygen, nitrogen & phosphorus
- types: - deoxyribonucleic acid (DNA) [contains deoxyribose sugar]
- ribonucleic acid (RNA) [contains ribose sugar]
36
What are nucleotides made up of? (3)
- a pentose sugar (5-carbon sugar) [ 2 types: ribose & deoxyribose]
- nitrogenous base
- phosphate group
[combined together through condensation process]
37
What are the 5 nitrogenous base?
- adenine (A)
- guanine(G)
- cytosine (C)
- thymine (T)
- uracil (u)
38
What are the characteristics of deoxyribonucleic acid (DNA)? (4)
- consists 2 polynucleotide chains intertwined in opposite directions, forming the double helix
- nitrogenous base groups on both polynucleotide chains are matched & bound together by hydrogen bonds
- nitrogenous base for DNA: - adenine(A) with thymine (T)
- guanine (G) with cytosine (C)
39
What are the characteristics of ribonucleic acid (RNA)? ()
- single polynucleotide chain shorter than DNA
- nitrogenous bases for RNA: - adenine
- guanine
- cytosine
- uracil
40
What are the 3 main types of RNA involved in the protein synthesis process?
- messenger RNA (mRNA)
- ribosomal RNA (rRNA)
- transfer RNA (tRNA)
41
What is the importance of nucleic acids in a cell? (3)
DNA
- carrier of hereditary information
- determinant of characteristics in living organisms
- contains genetic codes carried by nitrogenous bases (A,G,C,T) for polypeptide synthesis which form proteins
42
Explain an example of genetic code. (4)
- genetic code is written in a series of 3 bases that determine sequence of amino acids in proteins to be synthesised
Example:
-AUG codon on mRNA is the code for methionine acid
- the 3-base sequence in DNA is transcribed into mRNA codons, then translated into the amino acid sequence to form a single polypeptide chain
- means that the sequence of nucleotides in DNA determines the amino acid sequence in the polypeptide chain that builds the corresponding protein
43
Explain the formation of chromosomes from DNA & proteins. (4)
- chromosomes are formed from DNA polynucleotide chains that are wound around a protein called histone
- histones don't carry genetic information
- DNA molecules combine with histone proteins to form nucleosomes
- nucleosomes are intertwined to form the chromosome structure
