Cell Membrane and Nucleus Overview

Cell Membrane

• The cell membrane is a selectively permeable barrier enclosing the cell's contents.
• Primarily composed of a phospholipid bilayer, with embedded proteins and cholesterol.
• Hydrophobic tails of phospholipids face inward, hydrophilic heads face outward.
• This structure regulates substance passage into and out of the cell.
• Membrane proteins act as channels, pumps, receptors, and enzymes, influencing cell communication and transport.
• Membrane fluidity is crucial, affected by temperature and lipid composition.
• Maintains a concentration gradient, enabling active and passive transport.

Nucleus

• The nucleus is the cell's control center.
• Houses the cell's genetic material (DNA) organized into chromosomes.
• DNA is surrounded by proteins compacting and regulating access.
• Enclosed by a double membrane (nuclear envelope) with nuclear pores for molecule transport.
• Nucleolus within the nucleus is responsible for ribosome assembly.
• Regulates gene expression, influencing protein synthesis and cell activities.

Mitochondria

• Mitochondria are the "powerhouses" of the cell.
• Responsible for cellular respiration, generating ATP, the cell's primary energy currency.
• Possess their own DNA and ribosomes, suggesting an evolutionary origin as a separate organism.
• Double-membraned organelles, with an inner membrane folded into cristae for increased surface area.
• Cristae contain enzymes for the electron transport chain in cellular respiration.
• Mitochondrial malfunction significantly impacts energy production and overall cell health.

Ribosomes

• Ribosomes are the cell's protein synthesis machinery.
• Composed of ribosomal RNA (rRNA) and proteins.
• Can be free-floating in the cytoplasm or bound to the endoplasmic reticulum (ER).
• Free ribosomes synthesize proteins for use within the cell.
• Bound ribosomes synthesize proteins destined for secretion or membrane insertion.
• Protein synthesis involves tRNA (bringing amino acids) and mRNA (instructions).

Endoplasmic Reticulum (ER)

• The endoplasmic reticulum (ER) is a network of membranes throughout the cytoplasm.
• Continuous with the nuclear envelope, crucial for protein and lipid synthesis.
• Rough ER is studded with ribosomes, involved in protein synthesis and modification.
• Proteins synthesized on the rough ER often fold and modify within the ER lumen.
• Smooth ER lacks ribosomes, functions in lipid synthesis, detoxification, and calcium storage.
• The ER is involved in transporting molecules within the cell.

This quiz covers essential concepts of the cell membrane and nucleus. Learn about the structure, function, and importance of the cell membrane in regulating substances, as well as the nucleus's role as the cell's control center. Test your understanding of these fundamental cellular components.