BIO 12 Week in Review...

This is what happened this week in biology...

• MON- Started new unit on Digestive System by watching a video and researching some of the functions of the parts of the digestive system with the use of a sheet, created poetry? with those sheets, talked about marks (work handed back)
• TUES- Continued working on functions with the I-PADS and also created a blog post reflecting on our mark so far...
• THURS- UNIT 2 TEST (pretty good... a few tricky m.c. q's and a written q or two but overall I did really well), started Digestive System T-Shirts, notes on Digestive System
• FRI- Digestive System notes continued, digestive system colouring and q's, talked about what is to come this year (Playland, Reproduction, Marks, etc.)

BIO 12 UNIT 2: Study Notes

PROTEIN SYNTHESIS

• Transcription:

• Occurs in nucleus of eukaryotic cells
• Definition:
Making a mRNA from a DNA template
• STEP 1-
DNA Helicase unzips and unwinds a double-helix DNA molecule
• STEP 2-
RNA Polymerase aids in matching RNA nucleotides to the DNA template strand (only one of the two DNA strands) [COMPLIMENTARY BASE PAIRING]
• STEP 3-
Completed mRNA strand leaves the nucleus and goes to the ribosome (also, DNA is rewound)

• Translation:

• Occurs at the ribosome of eukaryotic cells

• Definition: Production of a protein

• STEP 1- mRNA attaches to the ribosome (this is the strand from the aforementioned process of Transcription) [INITIATION]

• STEP 2- tRNA: an amino acid head and anti-codon tail that complimentary pairs to a specific codon of the mRNA strand (3 a.a. group) that results in the release of its specific amino acid head (coded for via base pairing between anti-codon and mRNA codon); only two tRNA molecules are at the ribosome releasing their amino acids at one time 

• STEP 3- Peptide bonds form between each pair of amino acids 

• STEP 4- mRNA shifting along the ribosome similar to a conveyor belt in that two tRNA arrive, release the amino acid and than move away to allow a new tRNA to come and release its amino acid head and so on this process occurs at an extremely quick pace [ELONGATION]

• STEP 5- Emptied tRNA molecules (i.e. no amino acid head) leave the ribosome after releasing an amino acid (their job is done)

• STEP 6- The completed long strand of amino acid monomers joined together to form a protein designated for a very specific role in the cell relating to a chemical reaction (enzymes); [TERMINATION] occurs which basically breaks apart the ribosome and allows the protein to exit and go where it needs to go to complete its function in the cell 




Here is a video explaining Protein Synthesis...

http://www.youtube.com/watch?v=D3fOXt4MrOM



but really who needs that when I made my very own SHOW ME video (link on blog) ;)

BIO 12 UNIT 2: Study Notes

PROTEIN SYNTHESIS

• With the help of the above mRNA genetic codon table it is easy to move from a DNA sequence of codons to the mRNA and amino acids:

AAT GCG CTT CAT TAA ATT (DNA)

UUA  CGC  GAA GUA AUU UAA (mRNA)

Leu    Arg    Glu    Val    Iso   STOP (a.a.)

BIO 12 UNIT 2: Study Notes

PROTEIN SYNTHESIS

• Environmental Mutagens [MUTATIONS]:



• Radioactive residue/decay (gamma, alpha, beta particles/rays)

• UV Rays (exposure to sunlight)




Here is a brief but effective video...



http://www.youtube.com/watch?v=0wrNxCGKCws

BIO 12 UNIT 2: Study Notes

PROTEIN SYNTHESIS

• Mutations and their effects:

• Definition: A change in the base sequence of DNA
• Causes: Radiation exposure and chemicals [Mistakes in base pairing during P.S.]
• TWO MAIN TYPES:



• Point: Single nucleotide base changes in a gene's DNA sequence

• MISSENSE- single amino acid change within the protein (ex. sickle red blood cell; body not able to make blood as effectively and many  gain fatal diseases; TGT --> TGG is Cys --> Trp)
• NONSENSE- create a premature "stop" codon creating a shortened protein (ex. TGT --> TGA is Cys --> STOP; can cause diseases as serious as Cystic Fibrosis)
• SILENT- have no effects (i.e. no change) in amino acids of a protein (ex. GUU --> GUC is Valine; no changes just different base letters but coding for the same amino acid, common in Protein Synthesis)

• Frameshift: Occurs when bases are inserted or deleted from DNA sequence, shift in reading the frames of the codons which are differed as a result 

• ADDITION- the addition of an extra amino acid or more in the DNA sequence to create altered amino acid sequence and possibly non-functional proteins (ex. Huntington's disease caused by insertion of duplicates of triplet nucleotides)
• DELETION- making the sequence shorter, missing one or more bases leading to completely different codons and a.a.'s and possibly a non-functional protein (ex. Can cause many diseases/disorders including infertility for males)




Here are good videso discussing mutations...

http://www.youtube.com/watch?v=gQrq3CuPjxs&feature=results_video&playnext=1&list=PLD3C8F40032F0B234


http://www.youtube.com/watch?v=_tvP6iJEVH0

BIO 12 UNIT 2: Study Notes

TRANSPORT ACROSS THE CELL MEMBRANE

THE FLUID MOSAIC MODEL

PROPERTIES OF MEMBRANE:

• "Phospholipids" grout and "Proteins" tiles
• Pliable (vesicles bud off and fuse)
• Phospholipid Bi-layer has a certain fluidity 
• Asymmetrical (Phospholipids vertically face opposite directions of the membrane)

 STRUCTURAL COMPONENTS:

• PHOSPHOLIPIDS: main structural component, isolates cell cytoplasm from exterior, hydrophillic (head region) faces intracellular and extracellular fluids, hydrophobic (tail region) face eachother, allows and restricts molecules from enetering/exiting the cell 
• CHOLESTEROL: lipid embedded within membrane, makes bilayer stronger, more flexible, and less fluid, hydrophobic nature restricts water soluble molecules from penetrating the membrane
• GLYCOLIPIDS: phospholipids attached with a carbohydrate (straight or branched glucose sugar chains); provide cell with a specific recognition/ID marker to help prevent against certain diseases, illnesses, etc. from recurring

PROTEINS:

TWO MAIN TYPES: 

1. Integral--> Embedded within bilayer, hydrophobic regions embedded in membrane, hydrophillic regions extending from the bilayer

2. Peripheral--> Attached to the surface of membrane, held by protein filaments or free drifting laterally [MOSAIC]

• RECEPTOR: has a distinct binding site, molecular triggers that set off cell responses w/ specific molecules in extracellular fluid [Integral]
• GLYCOPROTEINS: proteins with an attached carbohydrate chain that projects externally from the membrane; ID/recognition markers [like glycolipids], cell surface attachment sites {Peripheral}
• TRANSPORT: regulate movement of water-soluble molecules through the membrane; Channel: form pores that allow smaller water-soluble molecules to penetrate the membrane & Carrier: have binding sites, require ATP energy to help move larger molecules across the membrane [Active Transport, Endo and Exocytosis] [Integral]

BIO 12 UNIT 2: Study Notes

TRANSPORT ACROSS THE CELL MEMBRANE

SELECTIVE PERMEABILITY

WHY IS THE MEMBRANE CONSIDERED SELECTIVELY PERMEABLE?

• It can choose what exits and enters the cell (unique mechanism), it chooses what the cell needs to perform specific functions/ what is best for the cell at the time, what it needs, prevents harmful substances from entering the cell.
• EXAMPLE: If the membrane only needs Potassium than it can and will only allow Potassium in the cell (channel)