bio 130- exam 2

Describe the structure and complementary base pairing of DNA.

Each DNA nucleotide is made up of a sugar, a phosphate group, and a nitrogenous base Base-pairing takes place between a purine and pyrimidine: namely, A pairs with T, and G pairs with C. In other words, adenine and thymine are complementary base pairs, and cytosine and guanine are also complementary base pairs

What is the same in the structure of the amino acids and what is different?

Each amino acid has the same structure: a central carbon atom (a.k.a. alpha carbon) bonded to an amino group, a carboxyl group, and a hydrogen atom They also have an additional variable atom/group of atoms bonded to the central carbon atom a.k.a. the R group. The R group is the only difference in structure between the 20 amino acids, otherwise they are identical to each other.

Is denaturation reversible? Or irreversible? When might this be the case?

For some proteins denaturation can be reversed, if the primary structure of the polypeptide is still intact (where the amino acids haven't split up yet), it may be able to re-fold into its functional form its if's returned to its normal environment. However, in other cases denaturation is permanent

Describe the structures of prokaryotic and eukaryotic ribosomes.

Ribosomes are responsible to protein synthesis; they are made of RNA and proteins complexes (known as the small and large subunits). The large subunit sits on top of the small subunit with an RNA template sandwiched between the two. (looks like a puffy hamburger with a puffy bun on top). In eukaryotes, ribosomes get their orders for protein synthesis from the nucleus, where portions of DNA are transcribed to mRNA. An mRNA travels to the ribosome, then uses the information to build proteins. Prokaryotes lack a nucleus, so their mRNAs are transcribed in the cytoplasm and are translated by ribosomes immediately.

Write the DNA strand that is complementary to this one: A T A T T C G C T A C T G T A C C G G T G T G A T

T A T AA G C G A T G A C A T G G C C A C A C T A

chargaffs rule syas the amount of A is equal to the amount of and the amount of G is equal to the amount of

T; C

What is the three letter nucleotide sequence called on a tRNA molecule?

anti codon

What can happen to a protein if it is subject to changes in temperature, pH etc.?

it can lead to denaturation and a loss of function

Describe the process of RNA processing

mRNA is first coated in RNA stabilizing proteins to prevent it from degrading while its processed and exported out of the nucleus, once the second step of transcription is complete (elongation), an enzyme adds a string of approx. 200 adenine residues to the 3' end, known as the poly A tail. This modification further protects the pre mRNA from degrading and signals to cellular factors that the transcript needs to be exported to the cytoplasm.

What are the basic characteristics of carbohydrates?

made up of carbon, hydrogen, and oxygen

DNA polymerase proofreads the strands as it is replicating. What is it called when these mistakes are not corrected?

mutations, a.k.a. a permemant change in the DNA sequence *mutations may lead to serious consequences (i.e. cancer)

secondary structure of protein

protein structure is formed by folding and twisting of amino acid chain either alpha helix or beta-pleating

tertiary structure of protein

protein structure is formed when the twists and folds of the secondary structure fold again to from a larger 3D structure

what is the function of rRNA?

rRNA molecules help hold ribosomal proteins in place and help locate the beginning and end of the mRNA message. They may also carry out the chemical reaction that joins amino acids together.

what is the complete name of RNA?

ribonucleic acid

what sugar is found in the backbone of RNA?

ribose

Describe monosaccharides and give examples

simple sugars - glucose, galactose (part of lactose), and fructose

nucleotides

simple sugars that make up nucleic acid

what is the basic structure of RNA?

single stranded molecule

primary structure of protein

the amino acid sequence of the polypeptide chain

Transcribe and translate the following DNA sequence (nontemplate strand): 5'-ATGGCCGGTTATTAAGCA-3'

transcription: UACCGGAAUAAUUCGU translation: Tyr/Arg/Asn/Asn/Ser/ U

what is the function of tRNA?

transfers amino acids to ribosomes; an interpreter molecule that understand both nucleic acid and the protein language

what is the function of a ribosome?

two main funtions: 1. decoding messages 2. forming peptide bonds

If the DNA of a sea anemone has 21% thymine, what is the percent of adenine, guanine and cytosine?

21% of A; 29% of G; 29% of C

If the DNA of a mouse has 22% adenine, what percent of the molecule is thymine?

22%

what are the four nitrogen bases in DNA?

1. Adenine 2. Thymine 3. Guanine 4. Cytosine

explain the process of initiation

1. DNA double helix unwinds partially for mRNA sequence to begin 2. the promoter is initiated and usually exists upstream of the genes that are being regulated *the job of the promoter is very important becuase it determines whether the corresponnding gene is transcribed

summarize the process of DNA replication

1. DNA unwinds at the origin of replication 2. new bases are added to the complimentary parental strands- one new strand is made continuosly, while the other is made in pieces 3. primers are removes, new DNA nucleotides are put in place of the primer and the backbone is seald by DNA ligase

what are the three steps of transcription?

1. Initiation 2. Elongation 3. Termination

what are the three types of RNA?

1. Messenger RNA (mRNA) 2. Transfer RNA (tRNA) 3. Ribosomal RNA (rRNA)

What are the four levels of protein structure?

1. Primary 2. Secondary 3. Tertiary 4. Quaternary

explain the process of elongation

1. RNA polymerase (an enzyme) proceeds along the DNA template adding nucleotides by base pairing with the DNA template in a manner similiar to DNA replication- the difference being that the RNA strand is being synthesized and does not remain bound to the DNA template. 2. the DNA is continuosly unwound ahead of the core enzyme and rewound behind it

What are the four nitrogen bases found in RNA?

1. adenine 2. uracil 3. guanine 4. cytosine

explain at least three functions that lipids serve in plants/animals

1. cells store energy for long time use 2. provide insulation from environment 3. bulding blocks for hormones

explain the process termination

1. once a gene is transcribed, the prokaryotic ploymerase needs to be intsructed to leave the DNA template. 2. there are two types of termination signals -both require repeated nucleotide sequences in the DNA template that result in RNA polymerase stalling, leaving the DNA template and freeing the mRNA transcript

If the DNA of a bacterium has 18% guanine, what percent of the molecule is cytosine?

18%

how many bonds are there between A and T? what kind of bonds are they?

2 bonds; hydrogen

Write the mRNA strand that would be transcribed from this DNA strand: T A C C C T G G A A G C G T G A G T C C T A T C

A U G G G A C C U U C G C A C UC A G G A U A G

explain what happens if even one amino acid is substituted in another polypeptide chain.

A change in gene sequence can lead to a different amino acid being added to polypeptide chain instead of the normal one. This causes a change in protein structure and function

quaternary structure of a protein

A number of polypeptide chains linked together, and sometimes associated with non-protein groups to form a protein.

Alternative RNA Splicing

A post transcriptional gene regulation mechanism in eukaryotes where multiple protein products are produced by a single gene through alternative splicing combinations of the RNA transcript

Nucleotide excision repair

A repair system that removes and then correctly replaces a damaged segment of DNA using the undamaged strand as a guide.

What is the initiation codon called that starts translation?

AUG or methionine

what are the two main types of nucleic acids?

DNA and RNA

Denaturation

Denaturation is a process in which proteins or nucleic acids lose the quaternary structure, tertiary structure and secondary structure which is present in their native state, by application of some external stress or compound such as a strong acid or base, a concentrated inorganic salt, an organic solvent

what sugar is found in the backbone of DNA?

Deoxyribose

Protein shape is critical for the function of proteins. Explain this statement.

Protein shape and its functions are intricately tied, any change in shape caused by changes in temperature or pH may lead to denaturation and a loss of function

what is the function of mRNA?

To carry information from DNA out of the nucleus to the site of protein synthesis

Describe disaccharides and give examples

a disaccharide are two monosaccharides that undergo dehydration (where the removal of a water molecule occurs) - lactose, maltose (malt sugar), sucrose (table sugar)

What type of bond is used to attach amino acids together? Describe this bond. (what type of reaction is used?)

a peptide bond is used to link amino acids together through a condensation reaction (meaning two hydrogen atoms link with an oxygen atom to form a water molecule while the rest of the amino acids link together)

which of the following does cytosine pair with? a. guanine b. thymine c. adenine d. a pyrimidine

a. guanine

Phospholipids are important components of ___________. a. the plasma membrane of cells b. the ring structure of steroids c. the waxy coverings on leaves d. the double bond in hydrocarbon chains

a. the plasma membrane of cells

The initial mechanism for repairing nucleotide errors in DNA is ________. a. mismatch repair b. DNA polymerase proofreading c. nucleotide excision repair d. thymine dimers

b. DNA polmerase proofreading ?

A promoter is ________. a. a specific sequence of DNA nucleotides b. a specific sequence of RNA nucleotides c. a protein that binds to DNA d. an enzyme that synthesizes RNA

b. a specific sequence of RNA nucleotides

DNA replicates by which of the following models? a. conservative b. semiconservative c. dispersive d. none of the above

b. semi conservative

the monomers that make up proteins are called __________. a. nucleotides b. disaccharides c. amino acids d. chaperones

c. amino acids

Prokaryotes contain a ________chromosome, and eukaryotes contain ________ chromosomes. a. single-stranded circular; single-stranded linear b. single-stranded linear; single-stranded circular c. double-stranded circular; double-stranded linear d. double-stranded linear; double-stranded circular

c. doube stranded circular ; double stranded linear

The RNA components of ribosomes are synthesized in the ________. a. cytoplasm b. nucleus c. nucleolus d. endoplasmic reticulum

c. nucleolus

An example of a monosaccharide is ____________. a. fructose b. glucose c. galactose d. all of the above

d. all of the above

Portions of eukaryotic mRNA sequence that are removed during RNA processing are ________. a. exons b. caps c. poly-A tails d. introns

d. introns

cellulose and startch are example of ___________. a. monosaccharides b. disaccharides c. lipids d. polysaccharides

d. polysaccharides

what is the complete name of DNA?

deoxyribonucleic acid

A deoxyribonucleotide is composed of 3 components: , and a .

deoxyribose, nitrogenous base, and a phosphate group

what is the basic structure of DNA?

double helix, sugar phosphate backbone

mixmatch repair

enzymes that recognize wrongly incorporated bases and remove them from DNA while replacing them with the correct bases

Describe polysaccharides

•Formed from repetition of condensation reactions, leading to long chain of monosaccharide units held together tightly by hydrogen bonding, making it ideal for storing energy •physically and chemically inactive - Starch (stored from sugars in plants), glycogen (storage from glucose in humans and vertebrae), cellulose (most abundant, natural biopolymers-cell walls are mostly made of this), chitin (used in exoskeletons of arthropods- insects, spiders, and crabs)