W16 L1 - Proteins and Genetic Code

Flashcards about proteins, amino acids, and the genetic code, based on the lecture notes.

What are proteins?

The class of major macromolecules relevant for biology that we will be focusing on.

What is the flow of information in a cell?

DNA to messenger RNA to proteins.

What are some of the functions of proteins in a cell?

Proteins catalyze reactions, provide structure, and transmit information.

How many different amino acids are proteins made of?

20

What is the basic structure of an amino acid?

A carbon connected to an acid function, a hydrogen, an amino group, and a variable R group.

What is the R group in an amino acid?

The variable group that gives each amino acid its particular characteristic.

Why can amino acids have stereoisomers?

The way the amino acids are built make the alpha carbon chiral.

What are L amino acids?

Amino acids where the amino group is on the left.

How are proteins made?

Proteins synthesized by the ribosome in the cell from a messenger RNA.

What is glycine?

The smallest amino acid, with an R group of H.

Does glycine have a stereoisomer?

No, because it has the same residue twice (H).

What is Cysteine?

An amino acid that is L but has R configuration.

What are the properties of isoleucine and leucine?

Nonpolar with aliphatic R groups, making them hydrophobic.

What are lysine, arginine, and histidine?

Amino acids with charges on the side chain.

Give examples of negatively charged amino acids.

Negatively charged amino acids include aspartate and glutamate.

What are aromatic amino acids?

Amino acids that have aromatic rings attached to them, like phenylalanine, tyrosine, and tryptophan.

What is a codon?

Three bases form one codon.

What is a reading frame?

The place where we start and continue along the sequence of the DNA.

How many potential reading frames can you have in a DNA sequence?

Six - three on the top strand and three on the complement.

How many different amino acids could we potentially encode with triplets/codons?

Four times four times four, which gives us 64 different combinations.

With what do we convert DNA sequences into protein?

A genetic code

What does it mean to say that the genetic code is redundant?

A genetic code is redundant because the same amino acid can be encoded by more than one codon.

Why do we need a start codon?

We need to tell a ribosome when to start with the amino acids so there is a start codon.

What is the start codon for every protein made in the cell?

ATG

What are the three stop codons?

TAA, TAG, and TGA

What are the three properties of the genetic code?

The genetic code is non-overlapping, degenerated or redundant, and universal.

What does it mean to say that a genetic code is universal?

Every organism uses the same genetic code. Every species has the asme codons.

Which codon is a stop codon in most species, but encodes tryptophan in yeast mitochondria?

TGA