Cells, Organelles, Transport, and Cell Division – Lecture Review

These flashcards cover major concepts from plasma membrane structure and organelles to transport mechanisms, cell signaling, and the stages of mitosis. They are formatted in Question-and-Answer style for efficient exam preparation.

What does it mean when the plasma membrane is described as "selectively permeable"?

It regulates what enters and exits the cell, allowing some substances to pass while blocking others.

Of what two main molecular components is the plasma membrane bilayer primarily composed?

Lipids (phospholipids) and embedded proteins.

Which structures in the plasma membrane serve as channels for active or passive transport?

Membrane proteins.

What is the primary role of the nucleus in a eukaryotic cell?

It acts as the control center that stores and protects genetic information (DNA).

What structure surrounds the nucleus and contains pores for molecular exchange?

The nuclear envelope with nuclear pores.

How does chromatin differ from a chromosome?

Chromatin is loosely coiled DNA present during interphase; chromosomes are tightly coiled DNA that form during cell division.

What is assembled in the nucleolus?

Ribosomes.

Which type of organelle synthesizes steroids, phospholipids, and fatty acids?

Smooth endoplasmic reticulum (SER).

Why does rough endoplasmic reticulum (RER) appear "rough" under a microscope?

It is studded with ribosomes on its surface.

What is the main function of ribosomes?

Protein synthesis.

Which organelle is often likened to a "post office" because it processes and ships proteins?

The Golgi complex (Golgi body).

What organelles are produced by the Golgi complex to digest foreign materials?

Lysosomes.

What is contained inside a lysosome?

Digestive enzymes.

What do vesicles and vacuoles primarily do within the cell?

Store and transport materials ("cargo") within the cell.

Where does cellular respiration occur in the cell?

In the mitochondria.

Name two structures found inside a mitochondrion that are key to its function.

Cristae (folded inner membrane) and matrix (internal fluid containing enzymes, DNA, and ribosomes).

List the three main components of the cytoskeleton.

Microtubules, microfilaments, and intermediate filaments.

Which hair-like structures move mucus out of the respiratory tract?

Cilia.

Which human cell type contains a flagellum and why?

Sperm cells; the flagellum propels them toward the egg.

What is the main difference between passive and active transport?

Passive transport requires no energy; active transport requires ATP.

Define diffusion in one sentence.

The net movement of molecules from an area of higher concentration to an area of lower concentration until equilibrium is reached.

Give two factors that increase the rate of diffusion.

Higher temperature or a greater concentration difference (also small molecule size, non-polar molecules, or shorter distance).

What is osmosis?

The movement of water across a selectively permeable membrane from a region of low solute concentration to high solute concentration.

In an isotonic solution, how does water move relative to a cell?

Water moves in and out at equal rates; no net change in cell volume.

What happens to a cell placed in a hypertonic solution?

Water leaves the cell, causing it to shrink (crenate).

What happens to a cell placed in a hypotonic solution?

Water enters the cell, causing it to swell (and possibly burst).

Describe the sodium–potassium pump.

An active transport system that uses ATP to move 3 Na⁺ ions out of the cell and 2 K⁺ ions into the cell.

What is phagocytosis often nicknamed, and what does it accomplish?

"Cell eating"; the cell engulfs large particles or microorganisms into vesicles for digestion.

How does pinocytosis differ from phagocytosis?

Pinocytosis ("cell drinking") engulfs extracellular fluid with dissolved solutes; phagocytosis engulfs large solid particles.

What is a ligand in cell signaling?

A small signaling molecule that binds to a receptor.

Outline the four basic steps of cell signaling.

Signal release, receptor binding (reception), signal transduction, and cellular response.

During which cell-cycle phase does the cell perform its normal functions and replicate DNA?

Interphase.

List the four stages of mitosis in order.

Prophase, metaphase, anaphase, telophase.

What key event characterizes metaphase?

Chromosomes align along the cell's equatorial (middle) plane.

During anaphase, what happens to sister chromatids?

They separate and move to opposite poles of the cell.

What is cytokinesis, and when does it occur?

Division of the cytoplasm via a cleavage furrow; it typically overlaps telophase.

What role do centrioles play in cell division?

They organize spindle fibers (microtubules) that help separate chromosomes.

Define sister chromatids.

Two identical DNA copies of a chromosome attached at a centromere before separation in mitosis.

What do motor proteins do during anaphase?

They move chromosomes along spindle fibers toward opposite poles.

What is the cleavage furrow composed of and what is its function?

Contractile microfilaments; it pinches the parent cell into two daughter cells during cytokinesis.