Chapter 3: The Cellular Level of Organization (9/8)

Cytoplasm

The material located between the plasma membrane and the nucleus, including cytosol and organelles.

Cytosol

The gel-like fluid component of the cytoplasm.

Organelles

Structures within the cytoplasm that perform specific cellular functions.

Cytoskeleton

Network of protein filaments that extend throughout the cytosol, providing shape and organization.

Centrosome

Microtubule organizing center near the nucleus consisting of a pair of centrioles and pericentriolar material.

Cilia

Short hair-like structures that beat rhythmically to move fluid across the cell surface.

Flagella

Long, whip-like structures that move an entire cell.

Ribosomes

Sites of protein synthesis, consisting of two subunits made of protein and ribosomal RNA.

Endoplasmic Reticulum

An organelle synthesizing glycoproteins and phospholipids (Rough ER) or fatty acids and steroids (Smooth ER).

Golgi Apparatus

Stacks of membranous sacs that modify, package, and distribute cellular products.

Lysosomes

Vesicles containing digestive enzymes for the breakdown of substances.

Peroxisomes

Organelles that contain enzymes to neutralize toxins and break down fatty acids.

Mitochondria

Organelles responsible for aerobic respiration and ATP production.

Nucleus

The control center for cellular operations containing DNA.

Plasma Membrane

Flexible barrier that surrounds the cell, regulating entry and exit of substances.

Tonicity

Describes how an extracellular solution influences the shape of body cells.

Active Transport

Process of moving substances across a plasma membrane against their concentration gradient, requiring energy.

Endocytosis

Process by which materials move into the cell in a vesicle.

Exocytosis

Process used to secrete cellular products into the extracellular environment.

Gene Expression

The process by which information from a gene is used to synthesize a functional gene product, often proteins.

Transcription

The process of copying genetic information from DNA to RNA.

Translation

The process of synthesizing proteins from mRNA, guided by tRNA.

Cell Division

The process by which cells reproduce themselves.

Apoptosis

A normal type of programmed cell death used by the body to remove unneeded cells.

Necrosis

Pathological type of cell death resulting from tissue injury.

Cyclin-dependent protein kinases (Cdk's)

Enzymes crucial for the regulation of the cell cycle, including DNA replication and mitosis.

Prophase

The stage of the mitotic phase during which chromatin condenses into chromosomes.

Metaphase

The phase of mitosis in which centromeres of chromosomes line up along the metaphase plate.

Anaphase

The phase of mitosis in which centromeres split and sister chromatids move toward opposite poles of the cell.

Telophase

The mitotic phase where the mitotic spindle dissolves, chromosomes regain their chromatin appearance, and a new nuclear membrane forms.

Free Radicals

Unstable atoms that can damage cells, causing illness and aging.

Gerontology

The scientific study of the process and problems associated with aging.

Gene

A functional unit of heredity that contains the instructions to synthesize a specific protein; consists of coding sequences (exons) and non-coding sequences (introns).

Genetic Code

A triplet code consisting of three nitrogenous bases that specifies amino acids during protein synthesis.

Transcription

The process occurring in the nucleus by which genetic information encoded in DNA is copied onto a strand of RNA to direct protein synthesis.

Isotonic Solution

A solution that has the same solute concentration as cellular fluid, resulting in no net water movement across the membrane and maintaining cell shape.

Hypotonic Solution

A solution with a lower solute concentration than the cell's cytoplasm, causing water to enter the cell, which leads to swelling and potential bursting.

Hypertonic Solution

A solution with a higher solute concentration than the cell, causing water to move out of the cell and leading to cell shrinkage (crenation).