Cellular Level of Organization - Membrane Transport and Cell Life Cycle

Flashcards covering cellular organization, membrane transport mechanisms, diffusion, osmosis, tonicity, carrier-mediated transport, vesicular transport, and the phases of the cell life cycle including interphase and mitosis.

What is the primary function of the plasma membrane?

It acts as a barrier separating cytosol and the extracellular fluid (ECF) and coordinates cellular activity with the extracellular environment.

Which term describes a membrane that allows some substances to cross but not others?

Selectively permeable.

What are the two overlapping ways to classify methods of moving substances into or out of a cell?

As passive or active, and as carrier-mediated or not.

What type of transport requires no ATP and moves substances down a concentration gradient?

Passive transport.

What type of transport requires ATP and moves substances against a concentration gradient?

Active transport.

Which transport mechanism uses a membrane protein to move substances across the membrane?

Carrier-mediated transport.

What is diffusion?

The continuous random movement of ions or molecules in a liquid or gas resulting in an even distribution.

What is a concentration gradient?

A condition where molecules are not evenly distributed, showing a concentration difference.

What types of substances can diffuse across the lipid bilayer of the plasma membrane?

Lipids, lipid-soluble molecules, and soluble gases (O2 and CO2).

What types of substances diffuse through membrane channels?

Water, small water-soluble molecules, and ions.

List four factors that influence diffusion rates.

Distance, molecule size, temperature, and gradient size.

What is osmosis?

The net diffusion of water across a membrane, maintaining similar overall solute concentrations between the cytosol and extracellular fluid.

What is osmotic pressure?

An indication of the force of pure water moving into a solution with a higher solute concentration.

What is tonicity?

A description of the effect of osmotic solutions on cell volume.

What is an isotonic solution?

A solution that does not cause osmotic flow across the membrane.

What is a hypotonic solution?

A solution that causes osmotic flow into a cell, potentially leading to hemolysis in red blood cells.

What is a hypertonic solution?

A solution that causes osmotic flow out of a cell, potentially leading to crenation in red blood cells.

Why is tonicity important in clinical settings, such as administering fluids to patients?

It affects cell volume through osmosis; for example, normal saline (0.9% NaCl) is isotonic with blood.

What is cotransport in carrier-mediated transport?

The movement of more than one substance in the same direction across a cell membrane.

What is countertransport in carrier-mediated transport?

The movement of two substances in opposite directions across a cell membrane.

What is facilitated diffusion?

A type of passive, carrier-mediated transport that requires no ATP and is limited by the number of available carrier proteins.

What is an example of active transport via a carrier protein?

The sodium-potassium pump (sodium-potassium ATPase).

What is vesicular transport?

A process where materials move across the cell membrane in small membranous sacs that form at or fuse with the plasma membrane, requiring ATP.

What are the two major types of vesicular transport?

Endocytosis and exocytosis.

What are the three forms of endocytosis?

Pinocytosis ('cell drinking'), Phagocytosis ('cell eating'), and Receptor-mediated endocytosis.

What is exocytosis?

The process where a vesicle discharges materials from inside the cell into the extracellular fluid (ECF).

What are the two types of cell division and their primary outcomes?

Mitosis, which produces 2 daughter cells each with 46 chromosomes, and Meiosis, which produces 4 sex cells each with only 23 chromosomes.

What is interphase in the cell life cycle?

The nondividing period during which a cell performs its normal activities or prepares to divide, duplicating chromosomes and synthesizing associated proteins.

What are the phases of interphase?

G0 (normal function, not preparing for division), G1 (cell growth, organelle duplication, protein synthesis), S (DNA replication, histone synthesis), and G2 (last-minute protein synthesis, centriole replication).

Briefly describe the process of DNA replication during the S phase.

DNA strands unwind, DNA polymerase binds and assembles new DNA strands by covalently linking nucleotides, resulting in two identical DNA strands.

What are the four phases of mitosis?

Prophase, Metaphase, Anaphase, and Telophase.

What happens during prophase?

Paired chromosomes become tightly coiled, and replicated centrioles move to opposite poles of the nucleus.

What happens during metaphase?

Chromosomes align at the metaphase plate.

What happens during anaphase?

Sister chromatids separate and are drawn along the spindle apparatus toward opposite ends of the cell.

What happens during telophase?

Cells prepare to enter interphase, the cytoplasm constricts (forming a cleavage furrow), nuclear membranes re-form, and chromosomes uncoil.

What is cytokinesis?

The physical separation of the cytoplasm, which begins with the formation of the cleavage furrow and concludes the end of cell division.