bio - Theme1Module3

What are the main roles of proteins in the cell?

transport proteins, enzymatic proteins, structural proteins, membrane protein, antibodies

What are polypeptides?

Polypeptides are chains of amino acids linked by peptide bonds.

how are polypeptides formed

amino acids are joined through condensation reactions where the carboxyl group of one amino acid bonds with the amino group of another releasing water.

components of amino acids

amino group, carboxyl group, R group

whats R group

the variable side chain that determines the amino acids properties and the proteins overall characteristics

what are the four levels of protein structure and what defines each?

primary structure, secondary structure, tertiary structure, quaternary structure

primary structure

linear sequence of amino acids in a polypeptide chain, determines all higher levels of protein structure

secondary structure

local folding patterns like alpha helices and beta sheets, stabilized by hydrogen bonds between the backbone atoms.

Tertiary Structure

the 3D shape of a protein, formed by interactions between R groups (e.g., hydrogen bonds, ionic bonds, hydrophobic interactions, and disulfide bridges).

Gives the protein its functional conformation.

Quaternary Structure

Assembly of multiple polypeptide chains into a functional protein complex. Example: Hemoglobin, a protein with four subunits.

Provide examples of proteins.

TATA-box binding protein, Porin proteins, Hemoglobin

TATA-box binding protein function

Has a specific groove that binds to DNA, initiating transcription.

Porin proteins

Form hydrophilic pores in membranes, allowing water and small molecules to pass through

Hemoglobin

a globular protein that increases solubility in the cytosol, facilitating oxygen transport in red blood cells.

What are the two main models for representing protein structures?

Space-filling Model, Ribbon Diagram

Space-filling Model

Represents the relative sizes and positions of all atoms in the protein.

Useful for visualizing molecular interactions.

Ribbon Diagram

Highlights the protein backbone and shows secondary structures like alpha helices and beta sheets. Useful for understanding protein folding and function

What are the main steps of protein synthesis?

transcription, translation

function of transcription

DNA is copied into RNA within the nucleus. Involves mRNA synthesis.

Translation

mRNA is translated into a polypeptide at ribosomes.

In prokaryotes, transcription and translation occur simultaneously.

In eukaryotes, mRNA undergoes processing (e.g., splicing) before translation in the cytoplasm.

What are the roles of the nucleus and ribosomes in protein synthesis?

Nucleus, Ribosomes

function of Nucleus

Houses DNA and coordinates transcription.

The nucleolus produces ribosomal RNA (rRNA) and assembles ribosomal subunits.

function of Ribosomes

Synthesize proteins.

Free ribosomes make cytosolic proteins.

ER-bound ribosomes produce proteins for secretion or membrane integration.

How does protein folding occur, and what determines the final shape?

• Process:

  • Folding occurs during and after translation, driven by the primary amino acid sequence.

• Key Levels of Folding:

  1. Secondary structure: Stabilized by hydrogen bonds.

  2. Tertiary structure: Determined by interactions between R groups.

  3. Molecular chaperones: Assist in proper folding to prevent misfolding and aggregation.

How does the endomembrane system process and transport proteins?

1. Synthesis:

   • Proteins are synthesized in the rough ER.

2. Modification:

   • Glycosylation (addition of carbohydrate groups) enhances stability and function.

3. Transport:

   • Proteins are packaged into vesicles and sent to the Golgi apparatus for further processing.

4. Targeting:

   • Modified proteins are tagged for delivery to specific cellular locations (e.g., secretion or organelles).

What are examples of key proteins and their specific functions?

• Aquaporins:

  • Facilitate rapid water transport across membranes.

  • Have hydrophilic interiors for water and hydrophobic exteriors for membrane integrity.

• CFTR (Cystic Fibrosis Transmembrane Conductance Regulator):

  • Ion channel regulating chloride ions in cells.

  • Mutations cause cystic fibrosis, leading to thick mucus buildup in lungs and digestive issues.

What are the key takeaways about proteins and their cellular roles?

1. Proteins have diverse roles, such as transport, signaling, and enzymatic activity.

2. The unique structure of a protein determines its function.

3. The endomembrane system is vital for protein modification and transport.

4. Ribosomes (cytosolic and ER-bound) are crucial for synthesizing and folding proteins.