Bio 111 Recitation quiz #4 Purdue

Which structures are formed by hydrogen bonding in the peptide backbone?

2ndary structures

What is the highest level of structure that an individual/single protein can be?

3 - tertiary

What are tertiary structures stabilized by?

Tertiary structures are stabilized by interactions between R groups and amino acids.

What types of R groups are stabilized between interactions between R groups and amino acids in a tertiary structure?

R groups=

- Hydrogen bonds

- Ionic bonds

What are electrostatic interactions?

- Hydrogen bonds between R groups

- Ionic bonds between R groups

What do disulfide bridges have?

cysteines

Which stabilizing tertiary structure has covalent bonds?

disulfide bridges

Which interaction is because of the charge fluctuations in the electron clouds of the atoms?

Van der Waals interaction

What is a Van Der Waals interaction?

a weak interaction between non-polar molecules

What are hydrophobic interactions?

R groups will fold into interior of protein to avoid the aqueous environment

What are domains?

Subunits within a protein that carry out specific functions

What is the highest level of structure for a single/individual protein?

tertiary

What is the interaction of multiple proteins into multi-protein complexes?

quaternary

What are chaperone proteins?

Enzymes that help proteins fold and/or refold into the proper shape

What is epigenetics?

It changes the expression of the genes without changing the DNA sequence of the genes.

What do epigenetic changes often change?

Epigenetic changes often change the chromatin structure of a gene

What are Epigenetic modifications?

change how tightly DNA and histones bind to each other -> which affects gene expression

What is Euchromatin?

DNA and histones are LOOSELY associated and DNA is VERY accessible to transcription factors/RNA polymerase binding.

This means that genes will be expressed.

What is Heterochromatin?

DNA and histones are TIGHTLY associated and DNA is NOT very accessible to transcription factors/RNA polymerase.

This means that the genes will not be expressed.

What is chromatin remodeling?

changes to the chromatin state due to epigenetic modifications

What is Histone Acetylation?

negatively charged acetyl groups are attached to lysine in the amino-terminal tails of histones

Histones

positively charged which makes them attracted to DNA (which is negative)

Acetyl group added to the histone

since the acetyl group is negatively charged, when it is added to the positively charged histones, it makes the histone more negative.

when the histone is now more negative-> it causes it to be less attracted to the DNA which makes it pull apart and puts it in a more euchromatin state (loosely together)-> genes are expressed.

Histone acetylation=

gene expression

more euchromatin state

What attaches to lysine in the amino-terminal tails of histones?

acetyl groups

Acetyl groups attach to what?

lysine in the amino-terminal tails of histones

What acetylates histones?

HATS

What deacetylate or take away acetyl groups?

HDACS

What do HDACs do to histone tails and what does that result in?

they take away acetyl groups which would make the histone more positive which would make it bind to dna more which would make everything tighter and force it to be in a more heterochromatin state -> no genes would be expressed

What is DNA methylation?

DNA methylation is when a methyl group is added to a cytosine in DNA

When a methyl group is added to cytosine it acts as a physical barrier to the binding of transcription factors which results in no gene expression because no DNA can bind to it.

What inhibits gene expression?

DNA methylation

Acetylation vs Methylation

Acetylation: expresses the gene by adding negative to positive histone

Methylation: inhibits gene expression by adding a cytosine in DNA acting as a physical barrier to prevent DNA from binding to it

Methyl

attracts HDCAS-> which remove acetyl groups from histones causing it to be more tightly wound to DNA which makes it in a heterochromatin state which does not allow for gene expression

Hyperacetylation

euchromatin state

histones are more negatively charged which make it less attracted to DNA and pulls it apart so genes can be expressed

Only cytosines that are followed by _____ are methylated

Only cytosines that are followed by a guanine are methylated.

Cytosines that are methylated are ___

- cytosine that comes before/proceeds the guanine

which mean that the guanine is after the cytosine

What epigenetic modification does heterochromatin do?

- hypoacetylation of histones

- hypermethylation of DNA

- inhibits gene expression

Euchromatin is what?

- hyperacetylation of histones

- hypomethylation of DNA

- promotes gene expression