Water properties: adhesion, cohesion, capillary action, surface tension, high specific heat
Acidic - lots of H+, Basic - lots of -OH
Carbohydrates: CHO, 1 C : 2 H : 1O
Proteins: CHONS, made of amino acids (amine group, carboxyl group, R group)
Lipids: CHOP, also includes phospholipids & steroids, not true polymers, double bonds in fatty acids means unsaturated
Nucleic acids: CHOPN, made up of three parts: a phosphate group, a 5-carbon sugar, and a nitrogenous base. The nitrogenous base can be either a purine (adenine or guanine) or a pyrimidine (cytosine, thymine or uracil).
Surface Area to Volume Ratio - high ratio means more efficient exchange with outside environment.
Need to know eukaryotes vs prokaryotes.
Plasma membrane: selectively permeable, need to know about integral proteins, aquaporins, glycoproteins, and glycolipids.
Hypertonic - cell shrivels due to high solutes outside, hypotonic - cell bloats due to low solutes outside
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DNA is made up of repeated subunits of nucleotides. Each nucleotide has a five-carbon sugar, a phosphate, and a nitrogenous base.
The name of the pentagon-shaped sugar in DNA is deoxyribose.
adenine—a purine (double-ringed), guanine—a purine (double-ringed), cytosine—a pyrimidine (single-ringed), thymine—a pyrimidine (single-ringed), uracil - a pyrimidine (single-ringed)
Adenine pairs up with thymine (A–T) by forming two hydrogen bonds.
Cytosine pairs up with guanine (G–C) by forming three hydrogen bonds.
The 5′ end has a phosphate group, and the 3′ end has an OH, or “hydroxyl,” group.
The 5′ end of one strand is always opposite to the 3′ end of the other strand. The strands are therefore said to be antiparallel.
DNA helix twists and rotates during DNA replication, another class of enzymes, called DNA topoisomerases, cuts, and rejoins the helix to prevent tangling.
To start off replication, an enzyme called RNA primase adds a short strand of RNA nucleotides called an RNA primer.
DNA polymerase works in the 3’ to 5’ direction while new nucleotides are added in the 5’ to 3’ direction
However, when the double-helix is “unzipped,” one of the two strands is oriented in the opposite direction—3′ to 5′.
Because DNA polymerase doesn’t work in this direction, the strand needs to be built in pieces.
The lagging strand is built in the opposite direction of the way the helix is opening, so it can build only until it hits a previously built stretch. Once the helix unwinds a bit more, it can build another Okazaki fragment.
Messenger RNA (mRNA) is a temporary RNA version of a DNA recipe that gets sent to the ribosome.
Ribosomal RNA (rRNA) makes up part of the ribosomes.
Transfer RNA (tRNA) brings amino acids to the ribosomes. It brings the brings a specific amino acid into place at the appropriate time by matching anticodons to codons. It does by reading the message carried by the mRNA.
The strand that serves as the template is known as the antisense strand.
The other strand that lies dormant is the sense strand, or the coding strand.
RNA polymerase builds RNA by adding nucleotides only to the 3′ side, therefore building a new molecule from 5′ to 3′
In eukaryotes, the introns must be removed before the mRNA leaves the nucleus. This process, called splicing, is accomplished by an RNA-protein complex called a spliceosome. In addition, a poly(A) tail is added to the 3′ end and, a 5′ GTP cap is added to the 5′ end.
Initiation: The start codon is A–U–G, which codes for the amino acid methionine. The tRNA with the complementary anticodon, U– A–C, is methionine’s personal shuttle; when the AUG is read on the mRNA, methionine is delivered to the ribosome.
Elongation: Addition of amino acids is called elongation and when many amino acids link up, a polypeptide is formed.
Termination: The synthesis of a polypeptide is ended by stop codons. There are three that serve as a stop codon. Termination occurs when the ribosome runs into one of these three stop codons.
Structural genes code for enzymes needed in a chemical reaction. These genes will be transcribed at the same time to produce particular enzymes.
The promoter gene is the region where the RNA polymerase binds to begin transcription.
The operator is a region that controls whether transcription will occur; this is where the repressor binds.
The regulatory gene codes for a specific regulatory protein called the repressor. The repressor is capable of attaching to the operator and blocking transcription.
Post-transcriptional regulation occurs when the cell creates an RNA, but then decides that it should not be translated into a protein. This is where RNAi comes into play.
RNAi molecules can bind to an RNA via complementary base pairing. This creates a double-stranded RNA
Post-translational regulation can also occur if a cell has already made a protein, but doesn’t yet need to use it.
Base substitution (point) mutations result when a single nucleotide base is substituted for another. There are three different types of point mutations:
Nonsense mutations cause the original codon to become a stop codon, which results in early termination of protein synthesis.
Missense mutations cause the original codon to be altered and produce a different amino acid.
Silent mutations happen when a codon that codes for the same amino acid is created and therefore does not change the corresponding protein sequence.
Retroviruses like HIV are RNA viruses that use an enzyme called reverse transcriptase to convert their RNA genomes into DNA so that they can be inserted into a host genome.
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