lecture 6: biomolecules part 2

Question 1

What is a protein?

Answer 1

Biologically functonal molecule that consists of one or more polypeptides + associated cofactors
- Very diverse functions

Question 2

What are do proteins do? (8 functions)

Answer 2

1. Enzymatic proteins: biological catalysts —> accelerate chemical reactions
2. Defensive proteins: protection against infection, disease, other life-threatening events
3. Storage proteins: storage of amino acids
4. Transport proteins: transport of substances around the body in and out of cells
5. Regulatory proteins: regulate cellular activities (cell division)
6. Communication proteins: response of cell stimuli and communication between cells
7. Motor proteins: movement of body, cell or components in cells
8. Structural proteins: production of structural components —> provide support and protection

Question 3

What are polypeptides?

Answer 3

Unbranched polymers built from same set of 20 amino acids

Question 4

What are amino acids and what do they constist of?

Answer 4

• Organic molecules with carboxyl and amino groups + Side chain (R group)
• All amino acids = same amino group and carboxyl group, but differs in R group

Question 5

What are the 3 major classes of amino acids?

Answer 5

• Difference in the R group*
  1. Nonpolar (hydrophobic): C-H bonds = nonpolar covalent bonds
  2. Polar Uncharged (hydrophilic): O-H, N-H = polar, but no charges
  3. Charged acidic/Charged basic (hydrophilic): acidic = negative charge and basic = positive charge

Question 6

What is proteins’ primary structure?

Answer 6

1 polypeptide chain —> repeating amino acids joinded by peptide bonds with side chains hanging on the side

Question 7

What are proteins’ higher levels of structure?

Answer 7

Tieriary structure (&secondary = the different subsections)
Quaternary (not all attain this level)

Question 8

What consists of a functional protein?

Answer 8

Consists of one or more polypeptides precisely twisted, folded, and coiled into a unique shape

Question 9

Are proteins diverse in structures?

Answer 9

Yes. As “structure fits functions” and as proteins are very diverse in functions, they are also diverse in structures. Proteins are the most structurally diverse class of molecules known.

Question 10

What is sickle-cell disease?

Answer 10

• Genetic blood disease that results from a single amino acid substitution in one polypeptide of the protein hemoglobin.
• Usually, the molecules of a normal hemoglobin do not associate with each other as they carry oxygen. The red blood cell is smooth and caved in, allowing it to travel in blood vessels.
• The molecules of a sickle-cell hemoglobin crystallize into a fiber causing its capacity to carry oxygen to be reduced. The red blood cell’s structure is compromised and does not allow it to travel smoothly in blood vessels.

Question 11

What is the consequence of a slight change in the sequence of amino acids in a polypeptide (the primary structure)?

Answer 11

A slight change in the primary structure can affect all of a protein’s higher levels of structure and its ability to function

Question 12

How do changes to the physical and chemical environment affect a protein’s structure?

Answer 12

Can interfere with bonds that form upper level structures of a protein and cause a protein to come apart (denaturation)

Question 13

What is denaturation and renaturation?

Answer 13

• Loss of protein’s natural structure —> misfolding of the protein
• Can be reversible or irreversible depending on magnitude of change
• Renaturation = protein regains natural structure
• A denatured protein is biologically inactive.

Question 14

What is a nucleic acid and what does it consists of?

Answer 14

• Genetic material in all cells (and viruses)
• Also many are functional molecules with many important functions in cell
• Composed of one or more unbranched polymers called “polynucleotides”

Question 15

What are the 2 types of nucleic acids?

Answer 15

1. Deoxyribonucleic acid (DNA)

2. Ribonucleic acid (RNA)

Question 16

What does DNA do (5 elements)?

Answer 16

1. Acts as genetic material in all cells that can…
2. Carry information
3. Be replicated
4. Be transmitted to offspring (genetic & heredity)
5. Be changed by mutation (genetic diseases)

Question 17

What informations (3) is in DNA?

Answer 17

1. Directions for its replication
2. Units called genes that encode sequence of specific polypeptides and other gene products
3. Directions for using genes

Question 18

What do genes do?

Answer 18

Expression of our genes in a genetic program gives rise to our development program which gives us our species’ chracters & indivudal traits
- Genes are heritable units passed on to our offspring

Question 19

What does RNA do (3 main functions)?

Answer 19

RNA = big players in gene expression

1. Messenger RNA (mRNA): copied from genes + provide information for translation of a nucleic acid sequence into a polypeptide sequence
2. Ribosomal RNA (rRNA): makes up part of the ribosome (protein synthesis machinery)
3. Transfer RNA (tRNA): adaptor molecules in protein synthesis

Question 20

What are the steps of gene expression?

Answer 20

1. DNA (gene)
   Transcription in nucleus
2. Synthesis of mRNA —> mRNA
   Movement of mRNA into cytoplasm
   Translation of nucleic acid sequence into polypeptide sequence (with ribosomes and tRNA)
3. Synthesis of protein —> Protein (polypeptide)

Question 21

What are polynucleotides made of?

Answer 21

Polynucleotide is made of monomers called nucleotides

Question 22

What are the 4 different types of nucleotides in DNA and in RNA?

Answer 22

DNA: Cytosine (C), Guanine (G), Adenine (A), and THYMINE (T)
RNA: Cytosine (C), Guanine (G), Adenine (A), and URACIL (U)

Question 23

Nucleotide structure?

Answer 23

• Phosphate group
• 5-carbon sugar (Ribose in RNA and Deoxyribose (lose oxygen) in DNA)
• Nitrogeous bases (ATCG for DNA and AUCG for RNA)

Question 24

DNA structure?

Answer 24

• 2 polynucleotides spiraling around forming a double helix
• Double hexlix held together by complementary base pairing (by noncovalent bonds as it is easier to separate without damage)

Question 25

What is complementary base pairing?

Answer 25

Nitrogenous bases in nucleid acids interact through non-covalent hydrogen bonds
DNA: A-T pairs & C-G pairs
RNA: A-U pairs & C-G pairs

Question 26

What are the 3 steps of DNA replication?

Answer 26

1. Strand separation
2. Replication of each strand using opposite strand as a model + following base pairing rules
3. Polymerization: original DNA has been replicated

Question 27

What are the successive levels of DNA packaging?

Answer 27

1. Chromosome
2. Chromatin fiber
3. DNA wound on nucleosomes (beads on a string)
4. Double helix

Question 28

What are chromosomes?

Answer 28

• Highly ordered structures composed of chromatin fibers
• Each contains 1 long DNA molecule
• Each contains millions of base pairs
• Each contains hundred to thousand of genes

Question 29

How many chromosomes are there in one human cell?

Answer 29

23 pairs; based on size
XY = male
XX = female

Question 30

RNA structure?

Answer 30

• Single polynucleotide chains
• Single-stranded region froms loop
• Double-stranded region forms double helix
• Complementary pairing can occur between parts of same RNA molecule to form higher order structures

Question 31

Are RNA’s functions diverse?

Answer 31

Yes. Higher order structures lead to diverse 3D shape which lead to various functional classes (similar to proteins)

Question 32

What are the 3 differences between DNA and RNA?

Answer 32

1. Molecule level: DNA = double-stranded, RNA = single-stranded
2. Nucleotide level: DNA’s sugar = no Oxygen, RNA’s sugar = Oxygen present
3. Nucleotide level: DNA’s nitrogenous base = Thymine (T), RNA’s nitrogenous base = Uracil (U)