Proteins

Question 1

What is a peptide?

Answer 1

A short chain of amino acids linked by peptide bonds.

Question 2

Define polypeptide.

Answer 2

A longer chain of amino acids that can fold into functional proteins.

Question 3

What type of bond links amino acids in a polypeptide chain?

Answer 3

Peptide Bonds

Question 4

Peptide bonds are ________ and don’t rotate because of ____ bond character.

Answer 4

Planar, double bond

Question 5

What functions do short and long peptides serve?

Answer 5

Short peptides can function as hormones, while longer peptides form proteins.

Question 6

What does ‘steric’ refer to in molecular biology?

Answer 6

The spatial arrangement of atoms in a molecule.

Question 7

Describe the significance of hydrogen bonds in proteins.

Answer 7

They are weak bonds crucial for protein folding.

Question 8

What is protein folding?

Answer 8

The process by which a protein assumes its functional shape.

Question 9

What constitutes the primary structure of a protein?

Answer 9

The sequence of amino acids in a polypeptide chain.

Question 10

What characterizes the secondary structure of proteins?

Answer 10

Localized folding patterns, such as alpha helices and beta sheets.

Question 11

What is the tertiary structure of a protein?

Answer 11

The overall three-dimensional shape of a single polypeptide.

Question 12

Define quaternary structure in proteins.

Answer 12

The arrangement of multiple polypeptide chains into a functional protein complex.

Question 13

What charge does Glutamic acid carry at physiologic pH?

Answer 13

Glutamic acid carries a negative charge at a physiologic pH of 7.4.

Question 14

What charge does Arginine exhibit at physiologic pH?

Answer 14

Arginine carries a positive charge at a physiologic pH of 7.4.

Question 15

Where is Leucine typically found in soluble proteins?

Answer 15

Leucine is most likely found on the inside of the folded protein due to its hydrophobic nature.

Question 16

In membrane proteins, where is Leucine located?

Answer 16

In membrane proteins, Leucine is located in the portion that spans the membrane.

Question 17

What are the principal functions of proteins in biological processes?

Answer 17

Proteins catalyze reactions, facilitate signaling, serve structural roles, and coordinate energy transduction.

Question 18

How do proteins facilitate signaling in biological systems?

Answer 18

Proteins act through receptors and pathways to control and regulate biological processes.

Question 19

How can amino acid sequences be used to study protein relationships?

Answer 19

Comparing amino acid sequences reveals evolutionary and functional relationships among proteins.

Question 20

What properties of the peptide bond are important for protein structure?

Answer 20

The peptide bond has steric properties and hydrogen bond capabilities, crucial for secondary structure formation.

Question 21

What leads to the formation of over 100 types of amino acids in human proteins?

Answer 21

Modifications of the 20 standard amino acids result in over 100 types.

Question 22

What role do chemical groups play in protein functionality?

Answer 22

Cofactors, small molecules bound to proteins, modify and interact with proteins to influence functionality.

Question 23

What are some important biologically active derivatives derived from amino acids?

Answer 23

Histamine, L-DOPA, and thyroxine are important biologically active derivatives.

Question 24

What role does keratin play in the body?

Answer 24

It forms the structure of hair, nails, and skin.

Question 25

What are the essential components of the structural framework of organisms?

Answer 25

Fibrous proteins, especially collagen, are essential components in the structural framework.

Question 26

What is the function of collagen?

Answer 26

It provides strength and support in connective tissues.

Question 27

What amino acid repeats every third position in the collagen alpha chain?

Answer 27

Glycine repeats every third position in the collagen alpha chain.

Question 28

Why is Glycine special in the structure of collagen?

Answer 28

Glycine has only a hydrogen atom as its side chain, fitting into tight spaces in collagen.

Question 29

What is Osteogenesis Imperfecta?

Answer 29

A genetic disorder characterized by fragile bones due to collagen defects.

Question 30

What are amyloids in the context of protein study?

Answer 30

Abnormal protein aggregates that disrupt normal tissue function.

Question 31

How is Sickle Cell Disease caused?

Answer 31

By a mutation in the hemoglobin protein, leading to misshaped red blood cells.

Question 32

What is the primary purpose of Western Blot analysis?

Answer 32

To determine the presence of a specific protein and its approximate molecular weight.

Question 33

What limitation does Western Blot have concerning protein study?

Answer 33

It does not provide information about protein structure or activity.

Question 34

What is SDS-PAGE used for?

Answer 34

SDS-PAGE separates proteins based on their size.

Question 35

How does Western Blot relate to SDS-PAGE?

Answer 35

It uses antibodies to detect specific proteins in a sample after separation by SDS-PAGE.

Question 36

What information can a Western blot provide about a protein?

Answer 36

A Western blot provides information on protein presence, approximate molecular weight, and modified forms.

Question 37

What techniques are used to study protein structure at a molecular level?

Answer 37

Crystallography, NMR, and EM (Electron Microscopy).

Question 38

X-Ray Crystallography

Answer 38

- **What It Does:** X-ray crystallography involves bombarding a crystallized protein with X-rays and analyzing the diffraction pattern to determine the electron density. - **What It Tells Us:** Offers high-resolution 3D structures of proteins, revealing atomic-level details of the protein's shape and the arrangement of its atoms. This method is powerful for understanding the precise spatial arrangement of protein components.

Question 39

Nuclear Magnetic Resonance (NMR) Spectroscopy:

Answer 39

- **What It Does:** NMR uses the magnetic properties of atomic nuclei to determine the physical and chemical properties of atoms or molecules. - **What It Tells Us:** Provides detailed information about the structure, dynamics, and interactions of proteins in solution. NMR is particularly useful for studying proteins that are difficult to crystallize and for observing protein behavior in a more natural state.

Question 40

Electron Microscopy (EM)

Answer 40

- **What It Does:** EM uses a beam of electrons to image the sample, often used for studying large complexes or organelles. - **What It Tells Us:** Provides detailed images of protein structures, particularly useful for large protein complexes and membrane proteins that are challenging for X-ray crystallography or NMR. Cryo-EM, a variant, allows for near-atomic resolution structures without the need for crystallization.