Principles of Anatomy and Physiology - Chapter 3: The Cellular Level of Organization

Flashcards reviewing key concepts from Chapter 3: cell anatomy, plasma membrane, transport processes, organelle functions, protein synthesis, cell division (mitosis and meiosis), and cellular aging/disorders.

What are the three principal parts of a cell?

The plasma (cell) membrane, the cytoplasm (consisting of cytosol and organelles), and the nucleus (containing chromosomes and genes).

What is the lipid composition of the plasma membrane lipid bilayer?

The lipid bilayer consists of three types of lipid molecules: phospholipids ($75\%$), cholesterol ($20\%$), and glycolipids ($5\%$).

What are the two main classifications of membrane proteins based on their location in the lipid bilayer?

Integral (transmembrane) proteins, which extend into or through the lipid bilayer, and peripheral proteins, which are attached to the inner or outer surface of the membrane.

What are the six key functional types of membrane proteins shown in this diagram?

Ion channels, carriers (transporters), receptors, enzymes, linkers, and cell-identity markers (such as MHC proteins).

What is the function of receptor membrane proteins?

They serve as cellular recognition sites that recognize and bind specific molecules called ligands.

What is an electrochemical gradient across the plasma membrane?

A combined gradient consisting of a concentration gradient (difference in chemical concentration across the membrane) and an electrical gradient (difference in electrical charges across the membrane).

What five factors influence the rate of diffusion across a membrane?

1. Steepness of the concentration gradient, 2. Temperature, 3. Mass of diffusing substance, 4. Surface area, and 5. Diffusion distance.

Which types of substances cross the plasma membrane via simple diffusion?

Nonpolar, hydrophobic solutes such as oxygen, carbon dioxide, and nitrogen gases, fatty acids, steroids, and fat-soluble vitamins (A, D, E, and K), as well as small uncharged polar molecules like water, urea, and small alcohols.

What is the difference between channel-mediated and carrier-mediated facilitated diffusion?

In channel-mediated facilitated diffusion, a solute moves down its concentration gradient through a membrane channel; in carrier-mediated facilitated diffusion, a carrier (transporter) moves a solute down its concentration gradient across the membrane by undergoing a change in shape.

What occurs to a red blood cell when placed in hypotonic and hypertonic solutions?

In a hypotonic solution, water moves into the cell causing it to swell and burst (hemolysis); in a hypertonic solution, water moves out of the cell causing it to shrink (crenation).

What step-by-step process of primary active transport is illustrated in this diagram?

The sodium-potassium pump ($\text{Na}^+/\text{K}^+$ ATPase): 1. Three $\text{Na}^+$ ions bind to the inside of the pump, 2. ATP hydrolysis triggers a shape change that expels $\text{Na}^+$ outside, 3. Two $\text{K}^+$ ions bind to the outside surface, 4. Phosphate release causes the pump to return to its original shape, importing $\text{K}^+$ into the cell.

How do antiporters and symporters function as shown in this secondary active transport diagram?

Antiporters move $\text{Na}^+$ (or $\text{H}^+$) into the cell while moving another substance like $\text{Ca}^{2+}$ or $\text{H}^+$ out in opposite directions; symporters move $\text{Na}^+$ (or $\text{H}^+$) and another substance like glucose or amino acids in the same direction into the cell.

What are the six steps of receptor-mediated endocytosis?

1. Binding of ligands to receptors, 2. Vesicle formation (invaginated clathrin-coated pit), 3. Uncoating of the vesicle, 4. Fusion with an endosome, 5. Recycling of receptors to the plasma membrane, and 6. Degradation of contents in a lysosome.

What is phagocytosis, and which cell types act as the primary phagocytes?

Phagocytosis ("cell eating") is a form of endocytosis in which a cell engulfs large solid particles using pseudopods to form a phagosome; the main phagocytes are macrophages and neutrophils.

What is the difference between exocytosis and transcytosis?

Exocytosis releases materials from a cell using secretory vesicles that fuse with the plasma membrane; transcytosis combines endocytosis and exocytosis to transport a substance completely through a cell.

What three types of protein filaments are illustrated in this diagram from smallest to largest diameter?

(a) Microfilaments (generate movement and support microvilli), (b) Intermediate filaments (stabilize organelle positions and provide strength), and (c) Microtubules (determine cell shape and assist organelle and chromosome movement).

What is the structure and function of the centrosome?

Located near the nucleus, it consists of a pair of centrioles (cylindrical structures with nine clusters of microtubular triplets) surrounded by pericentriolar matrix; it functions as the microtubule organizing center for cell division.

How do cilia and flagella differ in movement and function?

Cilia are short, hair-like projections that move with an oar-like pattern to sweep fluid across a cell surface; flagella are longer projections that move in a wiggling, wave-like pattern to move an entire cell (e.g., sperm tail).

What is the primary function and structural location of ribosomes?

Ribosomes are composed of ribosomal RNA (rRNA) and proteins, and serve as the sites of protein synthesis; they can be free-floating in the cytoplasm or attached to the rough endoplasmic reticulum.

What are the structural and functional differences between rough ER and smooth ER?

Rough ER is studded with ribosomes and continuous with the nuclear envelope, synthesizing glycoproteins and phospholipids; smooth ER lacks ribosomes and synthesizes fatty acids and steroids, detoxifies drugs, and stores calcium ions in muscle cells.

What are the three structural parts of the Golgi complex, and what is its main function?

It consists of entry (cis) face saccules, medial saccules, and exit (trans) face saccules; it modifies, sorts, packages, and transports proteins and lipids received from the rough ER.

What are lysosomes, and what functions do autophagy and autolysis describe?

Lysosomes are Golgi-derived vesicles containing digestive/hydrolytic enzymes; autophagy is the digestion of worn-out cellular organelles, whereas autolysis is the digestion of an entire cell.

What enzymes do peroxisomes contain, and what are their primary roles?

Peroxisomes contain oxidases and catalase; they oxidize organic substances and fatty acids, and detoxify harmful substances such as hydrogen peroxide ($\text{H}_2\text{O}_2$).

What is the function of proteasomes?

Tiny, barrel-shaped structures containing proteases that degrade unneeded, damaged, or faulty proteins by cutting them into small peptides.

What structural features characterize a mitochondrion, and what is its main role?

It consists of an external membrane, an internal membrane folded into cristae, and a fluid-filled matrix; it is the site of aerobic cellular respiration producing most ATP and plays a role in apoptosis.

What are the main components of the nucleus?

The nuclear envelope (double membrane with nuclear pores), nucleoli (spherical bodies producing ribosomes), and chromatin (threads of DNA, proteins, and RNA that condense into 46 chromosomes in human somatic cells).

What occurs during transcription in protein synthesis?

Genetic information encoded in a DNA strand is copied onto a strand of RNA inside the nucleus to direct protein synthesis.

What occurs during translation in protein synthesis?

The nucleotide sequence of an mRNA molecule specifies the amino acid sequence of a protein, carried out by ribosomes in the cytoplasm.

What phases make up the somatic cell cycle depicted in this diagram?

Interphase (consisting of $G_1$ phase for organelle duplication, $S$ phase for DNA replication, and $G_2$ phase for final growth/protein synthesis) followed by the Mitotic (M) phase (Prophase, Metaphase, Anaphase, Telophase, and Cytokinesis).

What key events occur during the four stages of mitosis?

Prophase: chromatin condenses into chromosomes, nuclear envelope disappears, spindle forms; Metaphase: chromosomes align at the metaphase plate; Anaphase: centromeres split and sister chromatids move to opposite poles; Telophase: nuclear envelopes reappear and chromosomes uncoil.

What is cytokinesis?

The division of a cell's cytoplasm, during which a contractile ring forms a cleavage furrow to pinch the parent cell into two separate, identical daughter cells.

What key events take place during Prophase I and Anaphase I of Meiosis I?

In Prophase I, homologous chromosomes pair up (synapsis) to form tetrads and undergo crossing-over; in Anaphase I, paired homologous chromosomes separate to opposite poles (while sister chromatids remain attached).

What are the main outcome differences between Mitosis and Meiosis shown in this comparison diagram?

Mitosis produces two genetically identical diploid ($2n$) somatic cells from one division; Meiosis produces four genetically diverse haploid ($n$) gametes through two successive divisions (Meiosis I and Meiosis II).

What five specific types of cancer are identified in the chapter?

Melanoma, sarcoma, osteogenic sarcoma, leukemia, and lymphoma.