FoB lecture 7 - proteins & cell processes

What is the overarching concept of cellular processes discussed in Lecture 7?

Protein activity underlies cellular processes.

What happens to proteins when they bind to their substrates?

Proteins change shape, which is crucial for their function.

What is required for a protein to enter the nucleus?

A nuclear localizing signal (NLS) is required for nucleus entry.

What is the role of the nuclear pore complex?

It gates entry and exit into the nucleus.

What types of molecules can freely pass through the nuclear pore complex?

Small molecules like nucleotides can freely pass through.

what are Nuclear Exit signals (NES)?

different specific series of amino acids required for nucleus exit

*PRCOESS for proteins entering the nucleus*

Special shuttle proteins bing to the NLS sequence and carry the protein through the nuclear pore complex

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the shuttle proteins can bind to the protein fingers of the NPC, and they are pushed through to the nucleus

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once on the other side, the shuttle lets go of the protein cargo and now the protein can go do its job

What is the function of peroxisomes in cells?

Peroxisomes carry out redox reactions and detoxify the cell of lipids and alcohols.

What is the significance of the ER signal sequence?

It relocates proteins to the endomembrane system.

*PATHWAY from ER to outside of cell*

Protein enters ER while being synthesized by ribosome & is processed

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Protein exists ER (inside a vesicle & travels to cis face of golgi apparatus)

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protein enters golgi apparatus & is further modified

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protein exists golgi apparatus in a vesicle & moves to the plasma membrane

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protein is secreted from cell

How do proteins get sorted in the endomembrane system?

Proteins are tagged with specific amino acid sequences that direct them to their destinations.

What is the difference between exocytosis and endocytosis?

- Exocytosis sends molecules to the extracellular space

- endocytosis brings molecules into the cytoplasm.

What are the two types of endocytosis mentioned?

- Phagocytosis (engulfs large particles into the cell)

- Pinocytosis (brings in small dissolved substances or fluids).

What is receptor-mediated endocytosis?

process where molecules are brought in from the extracellular space by binding to receptor proteins in the cell membrane.

What is autophagy?

process where worn-out organelles are destroyed in the lysosome.

What are the roles of myosin, kinesin, and dynein in the cytoskeleton?

- Myosin motor proteins pull on actin

- Motor proteins also move cilia & flagella

- while kinesin and dynein move along microtubules.

what are cytoskeleton filaments made of?

protein subunits

What is the relationship between protein binding and cellular function?

The change in shape of a protein upon binding is fundamental to how proteins function.

What is the purpose of adding an NLS to a protein?

Adding an NLS will likely cause the protein to enter the nucleus.

How do shuttle proteins facilitate nuclear transport?

Shuttle proteins bind to the NLS sequence and carry the protein through the nuclear pore complex.

What is the function of integral membrane proteins in the Golgi?

They bind to localizing sequences to help sort proteins for their specific locations.

What is the significance of the specific series of amino acids in cellular transport?

They serve as tags that determine the destination of proteins within the cell.

What are the components found in the nucleus?

DNA, RNA (rRNA + mRNA), proteins, and hormones.

What is the function of lysosomes in cellular processes?

Lysosomes disassemble molecules brought in by endocytosis and recycle cellular components.

What is the role of the cytoskeleton in cells?

The cytoskeleton provides structure and facilitates movement within the cell.

What is the process of vesicular transport?

It involves the formation of vesicles that transport proteins and other molecules within the cell.

What is the function of the Golgi apparatus in protein sorting?

The Golgi apparatus modifies, sorts, and packages proteins for secretion or delivery to other organelles.

How do proteins enter the endomembrane system?

Proteins enter the endomembrane system through ribosomes that are bound to the rough ER

Why is it important to control what enters and exits the nucleus, and how is this achieved in eukaryotes?

- Controlling what enters and exits the nucleus is crucial for maintaining cellular function and regulating gene expression.

- This is achieved through the nuclear envelope, which contains nuclear pores that selectively allow molecules to pass based on size and signaling.

What determines whether a protein is synthesized in the cytoplasm by free ribosomes or attached to the ER?

The presence of a signal peptide at the beginning of the protein determines its synthesis location; proteins with a signal peptide are directed to the ER, while those without are synthesized in the cytoplasm.

How do proteins get sorted correctly in the Golgi apparatus?

Proteins are sorted in the Golgi based on their molecular tags or signals that direct them to their specific destinations, ensuring they are packaged into the correct vesicles.

What are the possible fates of a vesicle after it buds off the Golgi?

A vesicle can either fuse with the plasma membrane to release its contents outside the cell, deliver its contents to a lysosome, or return to the ER.

How do vesicles get to where they need to go?

Vesicles are transported to their destinations via motor proteins that move along cytoskeletal tracks, such as microtubules, ensuring accurate delivery within the cell.