Ch 3 Cellular Level of Organization

This set of flashcards covers key concepts and processes related to the cellular level of organization and functions found in the provided lecture notes.

What is the cell membrane?

The cell membrane is a selectively permeable barrier that surrounds the cell, controlling the entry and exit of substances while allowing communication and signaling between cells. It is composed of a phospholipid bilayer with embedded proteins.

What is a phospholipid bilayer?

A double layer of phospholipids that forms the fundamental structure of the cell membrane, providing a barrier to the passage of ions and molecules.

• It consists of two layers of phospholipid molecules arranged tail-to-tail. The hydrophilic (water-loving) phosphate heads face outward (towards the extracellular fluid and cytosol), while the hydrophobic (water-fearing) fatty acid tails face inward, forming a nonpolar interior.

What is Extracellular Fluid?

• The fluid external to cells, including interstitial fluid, plasma, and lymph. It provides nutrients and oxygen to cells and removes waste.

What is Intracellular Fluid?

The fluid within cells, also known as cytosol, which contains water, electrolytes, proteins, and various organic molecules. It plays a vital role in cellular processes and provides a medium for biochemical reactions.

What is a Phospholipid?

• An amphipathic molecule, meaning it possesses both hydrophilic and hydrophobic properties. It consists of a polar, hydrophilic phosphate-containing head group and two nonpolar, hydrophobic fatty acid tails.

  • Forms Phospholipid bilayer

What are membrane Proteins?

Proteins that are embedded in or attached to the phospholipid bilayer of cell membranes. They play key roles in communication, transport, and maintaining the structure of the cell.

2 Kinds of Membrane Proteins?

Integral and Peripheral Proteins

What are integral Proteins?

• embedded within or span the entire lipid bilayer, having both hydrophobic and hydrophilic regions. Many function in transport or signal transduction.

  • 4 Kinds include: channels, carriers, receptors, & glycoproteins

What do Channel Proteins do?

• Form hydrophilic pores that allow specific ions (e.g., Na+, K+, Cl-) or water molecules (aquaporins) to pass into or out of the cell down their concentration gradient.

What do Carrier Proteins do?

• Bind to specific substances and change shape to shuttle them across the cell membrane, facilitating transport against or along their concentration gradient.

  • Can be passive (Facilitated diffusion) or Active

What do Receptor Proteins do?

• Possess binding sites for specific extracellular signaling molecules (ligands), such as hormones or neurotransmitters. Binding induces a chemical reaction or a cascade of events inside the cell, relaying information.

What do Glycoproteins Do?

• These are integral proteins with carbohydrate groups (oligosaccharides) covalently attached to their extracellular surface. They are crucial for cell-cell recognition, adhesion (e.g., embryonic development, immune response), and forming part of the glycocalyx.

What is Glycocalyx

• A fuzzy-appearing, carbohydrate-rich coating on the exterior surface of the plasma membrane, formed by the carbohydrate portions of both glycoproteins and glycolipids. It plays vital roles in cell recognition, cell adhesion, protection from physical damage, and receiving signals.

What are Peripheral Proteins?

• These are proteins that are loosely attached to the exterior or interior surfaces of the plasma membrane, often involved in signaling pathways, maintaining the cell's shape, and facilitating connections between the membrane and cytoskeleton.

What are Selectively Permeable Membranes?

• The cell membrane acts as a selective barrier, allowing certain molecules to pass freely (e.g., small, nonpolar molecules like O2, CO2) while restricting others (e.g., large, polar, or charged molecules).

What is Passive transport?

Passive transport is the movement of molecules across a cell membrane without the need for energy input, relying on concentration gradients.

• Involves Facilited Diffusion, or Osmosis

What is diffusion?

• The net movement of particles from an area of higher concentration to an area of lower concentration, driven by the random motion of particles. This continues until equilibrium is reached.

What factors affect diffusion rates?

Factors affecting diffusion rates include temperature, concentration gradient, surface area, and the nature of the medium through which diffusion occurs.

What is facilitated Diffusion

• A type of passive transport where larger or polar molecules (e.g., glucose, amino acids, ions) move across the membrane with the help of specific transmembrane proteins (channel or carrier proteins). This still occurs down the concentration gradient and requires no ATP.

What is channel-mediated facilitated diffusion?

• Involves transmembrane channel proteins that selectively allow passage of specific ions or water molecules.

What is Carrier-mediated facilitated Diffusion?

• A type of facilitated diffusion that uses specific carrier proteins to transport larger or polar molecules across the cell membrane, moving them down their concentration gradient without using energy.

What is Osmosis?

• The specific diffusion of water molecules across a selectively permeable membrane from an area of higher water concentration (lower solute concentration) to an area of lower water concentration (higher solute concentration). The driving force is osmotic pressure.

What are aquaporins?

• Specialized channel proteins that facilitate the transport of water across the cell membrane, enhancing the process of osmosis.

What is Osmosis’s effect on cells?

• Can cause cells to swell and potentially lyse (burst) in a hypotonic solution (lower solute concentration outside the cell), shrink or crenate in a hypertonic solution (higher solute concentration outside the cell), or remain the same shape in an isotonic solution (equal solute concentration inside and outside the cell

What is Active Transport

• Requires cellular energy (ATP) to move substances across the membrane, typically against their concentration gradient (from low to high concentration). This is crucial for maintaining cellular ion gradients and absorbing nutrients.

What is primary active transport?

• A type of active transport that directly uses ATP to transport molecules against their concentration gradient, often involving specific pump proteins, such as the sodium-potassium pump.

What is Secondary Active Transport?

• Uses the energy stored in an ion's electrochemical gradient (established by primary active transport) to indirectly power the transport of another substance. It does not directly use ATP.

What does symport mean?

Symport refers to a type of secondary active transport mechanism where two substances are simultaneously transported in the same direction across a membrane, typically using the electrochemical gradient established by primary active transport.

What does Antiport mean?

A term in transport biology that refers to a mechanism where two substances are transported across a membrane in opposite directions, one moving into the cell while the other moves out.

What is bulk transport?

Bulk transport is a cellular process that involves the movement of large quantities of substances into or out of the cell via vesicles. This includes mechanisms such as endocytosis and exocytosis.

What is endocytosis?

• the process of a cell ingesting material by enveloping it in a portion of its cell membrane, and then pinching off that portion of membrane. Once pinched off, the portion of membrane and its contents becomes an independent, intracellular vesicle

What is Phagocytosis?

• "Cellular eating"; ingestion of large particles like bacteria or cellular debris.

What is Pinocytosis?

• "Cellular drinking"; the process where a cell engulfs liquid and small solutes by forming vesicles from the cell membrane.

What is Receptor Mediated Endocytosis?

• A specialized form of endocytosis in which cells internalize specific molecules based on their binding to surface receptors, leading to the formation of vesicles.

What is Exocytosis?

• The process of releasing substances from the cell; vesicles fuse with the plasma membrane and release their contents into the extracellular fluid (e.g., hormone secretion, neurotransmitter release).