Chapter 03 | Cells

Cell Composition

Cell Composition

Cells are composed of water, dissolved nutrients, organelles, and structures like the plasma membrane.

Cytoplasm

The internal living material of the cell, primarily composed of water, dissolved nutrients, and organelles.

Cytosol

The fluid portion of the cytoplasm that provides the medium for chemical reactions.

Cytoskeleton

A network of protein filaments that provide structural support, enable cell movement, and assist in intracellular transport.

Plasma Membrane

A thin, double-layered membrane composed of phospholipids, cholesterol, and proteins that acts as a selectively permeable barrier.

Phospholipid Bilayer

The arrangement of phospholipids with hydrophilic heads facing outward and hydrophobic tails facing inward.

Glycoproteins

Proteins with carbohydrate groups attached that are involved in cell recognition and communication.

Ribosomes

Sites of protein synthesis found free in the cytoplasm or attached to the rough endoplasmic reticulum.

Rough ER

Endoplasmic reticulum with ribosomes on its surface; involved in protein production and transport.

Smooth ER

Endoplasmic reticulum without ribosomes; synthesizes lipids and aids in detoxification processes.

Sarcoplasmic Reticulum

A type of smooth ER in muscle cells that stores calcium ions essential for muscle contraction.

Golgi Apparatus

Stacks of membrane-bound sacs that modify, sort, and package proteins produced by the ER.

Mitochondria

The powerhouse of the cell, responsible for ATP production, with a double-membrane structure.

Cristae

Folds of the inner membrane of mitochondria that increase surface area for chemical reactions.

Matrix (Mitochondria)

The innermost compartment of mitochondria containing enzymes for the Krebs cycle.

Lysosomes

Vesicles containing digestive enzymes that break down unwanted materials within cells.

Autophagy

Process by which lysosomes break down damaged organelles to recycle cellular components.

Centrosome

An organelle located near the nucleus that organizes the mitotic spindle during cell division.

Cilia

Hairlike projections capable of coordinated movement that help move substances along surfaces.

Microvilli

Small, fingerlike extensions of the plasma membrane that increase the surface area for absorption.

Flagella

Long, whip-like extensions used for cell motility; found in sperm cells.

Nuclear Envelope

Double membrane surrounding the nucleus, containing nuclear pores for substance exchange.

Nuclear Pores

Structures that allow the movement of RNA and ribosomal subunits out of the nucleus.

Nucleolus

A dense body within the nucleus where ribosomal RNA (rRNA) is synthesized.

Chromatin

A complex of DNA and proteins that condenses to form chromosomes during cell division.

Histones

Proteins that help package DNA into chromatin, regulating gene expression.

Gene Expression

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

Diffusion

Movement of molecules from high concentration to low concentration without energy expenditure.

Osmosis

A type of diffusion where water moves across a selectively permeable membrane in response to solute concentration.

Dialysis

Separation of small molecules from large ones through a selectively permeable membrane.

Filtration

Movement of water and solutes driven by hydrostatic pressure, crucial for kidney function.

Ion Pumps

ATP-driven protein pumps that move ions across the cell membrane against their concentration gradient.

Phagocytosis

The process where a cell engulfs large particles or pathogens, forming a vesicle that fuses with lysosomes.

Pinocytosis

A type of endocytosis involving the engulfing of fluid and dissolved substances into vesicles.

Cystic Fibrosis

A genetic disorder caused by malfunction in chloride ion transport, leading to thick mucus.

CFTR Protein

Defective chloride channel protein that disrupts water movement in cystic fibrosis.

Cholera

A bacterial infection that triggers chloride and water efflux from intestinal cells, causing dehydration.

DNA Structure

A double-helix structure made of nucleotide pairs (adenine with thymine, cytosine with guanine).

Sugar-Phosphate Backbone

The structural framework of DNA, holding the base pairs together.

Genes

Specific DNA sequences that encode proteins, which determine cell characteristics.

Transcription

The process of synthesizing messenger RNA (mRNA) from DNA.

RNA Polymerase

An enzyme that catalyzes the synthesis of mRNA from DNA.

Translation

The process where ribosomes synthesize proteins using mRNA and transfer RNA (tRNA).

Codons

Three-nucleotide sequences on mRNA that specify particular amino acids.

Anticodon

A sequence of three bases on tRNA complementary to an mRNA codon.

Point Mutations

Single nucleotide changes that can alter protein function.

Frameshift Mutations

Insertions or deletions that change the reading frame, leading to dysfunctional proteins.

Interphase

The period of growth and DNA replication between cell divisions.

Mitosis

The division of the nucleus into two genetically identical daughter nuclei.

Cytokinesis

Division of the cytoplasm, resulting in two separate daughter cells.

Hypertrophy

Increase in cell size resulting in larger tissue, such as muscle cells with exercise.

Physiological Hypertrophy

Exercise-induced hypertrophy, a normal increase in cell size.

Pathological Hypertrophy

Cardiac hypertrophy caused by hypertension.

Atrophy

Decrease in cell size, resulting in tissue shrinkage, such as muscle wasting.

Hyperplasia

Increase in cell number leading to tissue enlargement, such as callus formation.

Hormonal Hyperplasia

Breast tissue growth during pregnancy.

Anaplasia

Loss of cellular differentiation, typically seen in cancerous tissues.

Cancer

Uncontrolled cell growth resulting from mutations affecting cell cycle regulation.

Oncogenes

Genes that, when mutated, promote uncontrolled cell growth.

Tumor Suppressor Genes

Genes that inhibit uncontrolled growth; mutations can lead to cancer.