Cell Biology Plasma Membrane Quiz

Functions of the Plasma Membrane

• Acts as a physical barrier separating the cell from the extracellular fluid (ECF).
• Regulates the exchange of ions and nutrients, maintaining homeostasis.
• Contains receptors that enable the cell to respond to environmental changes.
• Provides structural support, contributing to tissue stability.

Membrane Lipids

• Composed of a phospholipid bilayer with both hydrophilic and hydrophobic regions.
• Contains cholesterol and steroids, enhancing membrane fluidity and stability.

Membrane Proteins

• Integral Proteins: Firmly embedded in the membrane; essential for structure.
• Peripheral Proteins: Loosely attached to the surface, easily separable.
• Anchoring Proteins: Stabilize membrane position by attaching to other structures.
• Recognition Proteins: Help the immune system identify normal vs. foreign cells.
• Enzymes: Catalyze biochemical reactions within the cell.
• Receptor Proteins: Bind specific ligands, initiating cellular responses.
• Carrier Proteins: Facilitate transport of solutes across the membrane.
• Channel Proteins: Form passageways for ions and small molecules to cross.

Membrane Carbohydrates

• Form the glycocalyx layer, which aids in lubrication, protection, and cell anchoring.
• Functions in recognition processes, distinguishing self-cells from pathogens.

Organelles

• Cytoskeleton: Provides strength, shape, and support for organelles; made up of microfilaments, intermediate filaments, and microtubules.
• Ribosomes: Sites of protein synthesis, can be free in cytoplasm or fixed to the ER.
• Endoplasmic Reticulum (ER): Network of membranes; includes rough (protein synthesis) and smooth (lipid synthesis) ER.
• Golgi Apparatus: Modifies and packages proteins for secretion or lysosomal use.
• Lysosomes: Contain digestive enzymes for breaking down waste and cellular debris.
• Peroxisomes: Contain enzymes for breaking down hydrogen peroxide and fatty acids.
• Mitochondria: Powerhouse of the cell; site of ATP production through aerobic metabolism.

Functions of the Nucleus

• Control center of the cell, managing protein synthesis and cellular functions.
• Surrounded by a nuclear envelope with pores for material transport.
• Stores genetic information as DNA; DNA is loosely coiled as chromatin in non-dividing cells.

Genetic Code

• Comprised of four bases (A, T, C, G) organized into codons (triplets), each coding for specific amino acids.
• Guides the synthesis of proteins, determining cell structure and function, and governs inheritance and mutation impact.

DNA and Protein Synthesis

• Involves transcription (creating mRNA from DNA) and translation (assembling polypeptides from mRNA).
• RNA polymerase facilitates mRNA synthesis from a DNA template.

Cellular Transport Mechanisms

• Diffusion: Movement of molecules from areas of higher concentration to lower concentration.
  • Simple Diffusion: Movement through the lipid bilayer.
  • Channel-Mediated Diffusion: Movement through protein channels for non-lipid soluble substances.
• Osmosis: Diffusion of water across a membrane towards higher solute concentration.
  • Tonicity Effects: Isotonic (no net change), hypotonic (cell swells), hypertonic (cell shrinks).

Carrier-Mediated Transport

• Uses integral membrane proteins for transporting substances, either passive or active.
• Facilitated Diffusion: Passive transport involving carrier proteins; no energy required.
• Active Transport: Uses ATP to move substances against concentration gradients.
  • Primary Active Transport: Direct ATP use (e.g., Na+/K+ pump).
  • Secondary Active Transport: Uses the concentration gradient of one substance to facilitate another.

Vesicular Transport

• Involves the movement of materials via vesicles.
  • Endocytosis: Process of taking substances into the cell; includes receptor-mediated endocytosis targeting specific molecules.