WEEK 2 BIOH111 EXAM QUESTIONS AND ANSWERS
WITH COMPLETE SOLUTIONS GRADED A++ LATEST
UPDATE
Tonicity (definition and types of solutions)
> Tonicity is a measure of a solution's ability to change the volume of cells by
altering their water concentration (osmosis)
Types of solutions with their effects on the cell :
1. Isotonic : Cell maintains shape and volume
2. Hypotonic : Cell swells and bursts (lysis)
3. Hypertonic : Cell shrinks (crenation)
Nucleus Function (Central Dogma)
Central Dogma - How our cells produce a protein
Steps
1. DNA (that’s found in the nucleolus of the nucleus)
DNA made up of : base triplet = sequence of 3 nucleotides (cytosine C, guanine G, and
thymine T)
- found in the nucleus
- double stranded (Double helix)
2. TRANSCRIPTION (DNA converted to RNA)
RNA (Rico-nucleic acid) Structure :
,- single stranded = the base triplet is not called a base triplet but a CODON = thymine
(T) cannot leave the nucleus as it is damaged easily so it becomes Uracil (U)
- it transcribes (takes a copy) of one of the strands of DNA from one particular start
base triplet (Codon) to an end base triplet
THE CODON = provides the codon of a particular amino acid, e.g. G + C + U = Alanine
3. The codons then get translated = into a protein
Protein = a sequence of amino acids which determines the structure and can happen
anywhere in the cell
Transcription
Process by which genetic information encoded in DNA is copied onto a strand of RNA
called messenger RNA (mRNA)
(different forms of RNA - (mRNA, rRNA - ribosomal RNA, tRNA - transfer RNA)
1. Initiation
Promoter region initiates transcription by RNA polymerase binding to a START base
triplet ATG (adenine, thymine, guanine)
2. Elongation
, RNAP reads a base triplet at a time and makes a complimentary (antisense) RNA
strand (mRNA) DNA only unwrapped at the site of transcription
3. Termination
RNAP stops transcribing when it reaches a STOP base triplet ( TAA, TAG, TGA)
Translation
The process of of reading the mRNA nucleotide sequence to determine the amino acid
sequence of the protein
Initiation : mRNA with a START codon (AUG) is first read by the ribosome with the
antisense tRNA anticodon (UAC) that carries
Plasma Membrane
A flexible yet sturdy barrier that surrounds and contains the cytoplasm of a cell.
Structure : * Fluid mosaic Model
- flexible, fluid (allows movement of proteins and lipids), selectively permeable
- Lipid bilayer = 2 parallel layers of molecules
. 75% phospholipids - polar, hydrophilic head and non-polar, hydrophobic tailes
. 20% choloesterol - interspersed among the other lipids
. 5% glycolipids - appear only in membrane that faces extracellular fluid
* Contains proteins
- Integral (extend into or through transmembrane)
WITH COMPLETE SOLUTIONS GRADED A++ LATEST
UPDATE
Tonicity (definition and types of solutions)
> Tonicity is a measure of a solution's ability to change the volume of cells by
altering their water concentration (osmosis)
Types of solutions with their effects on the cell :
1. Isotonic : Cell maintains shape and volume
2. Hypotonic : Cell swells and bursts (lysis)
3. Hypertonic : Cell shrinks (crenation)
Nucleus Function (Central Dogma)
Central Dogma - How our cells produce a protein
Steps
1. DNA (that’s found in the nucleolus of the nucleus)
DNA made up of : base triplet = sequence of 3 nucleotides (cytosine C, guanine G, and
thymine T)
- found in the nucleus
- double stranded (Double helix)
2. TRANSCRIPTION (DNA converted to RNA)
RNA (Rico-nucleic acid) Structure :
,- single stranded = the base triplet is not called a base triplet but a CODON = thymine
(T) cannot leave the nucleus as it is damaged easily so it becomes Uracil (U)
- it transcribes (takes a copy) of one of the strands of DNA from one particular start
base triplet (Codon) to an end base triplet
THE CODON = provides the codon of a particular amino acid, e.g. G + C + U = Alanine
3. The codons then get translated = into a protein
Protein = a sequence of amino acids which determines the structure and can happen
anywhere in the cell
Transcription
Process by which genetic information encoded in DNA is copied onto a strand of RNA
called messenger RNA (mRNA)
(different forms of RNA - (mRNA, rRNA - ribosomal RNA, tRNA - transfer RNA)
1. Initiation
Promoter region initiates transcription by RNA polymerase binding to a START base
triplet ATG (adenine, thymine, guanine)
2. Elongation
, RNAP reads a base triplet at a time and makes a complimentary (antisense) RNA
strand (mRNA) DNA only unwrapped at the site of transcription
3. Termination
RNAP stops transcribing when it reaches a STOP base triplet ( TAA, TAG, TGA)
Translation
The process of of reading the mRNA nucleotide sequence to determine the amino acid
sequence of the protein
Initiation : mRNA with a START codon (AUG) is first read by the ribosome with the
antisense tRNA anticodon (UAC) that carries
Plasma Membrane
A flexible yet sturdy barrier that surrounds and contains the cytoplasm of a cell.
Structure : * Fluid mosaic Model
- flexible, fluid (allows movement of proteins and lipids), selectively permeable
- Lipid bilayer = 2 parallel layers of molecules
. 75% phospholipids - polar, hydrophilic head and non-polar, hydrophobic tailes
. 20% choloesterol - interspersed among the other lipids
. 5% glycolipids - appear only in membrane that faces extracellular fluid
* Contains proteins
- Integral (extend into or through transmembrane)
