5 The Cell

Cell

The basic structural and functional unit of all living organisms, capable of performing all life processes.

Eukaryotic cell

A type of cell characterized by the presence of a nucleus and organelles, enclosed within membranes, found in plants, animals, fungi, and protists.

Prokaryotic cell

A type of cell lacking a true nucleus and membrane-bound organelles, usually smaller and simpler, typically found in bacteria and archaea.

Cytoplasm

The gel-like substance within the cell membrane, where organelles are suspended and cellular processes occur.

Selectively permeable

Describes a property of cell membranes that allows certain substances to pass while restricting others, maintaining homeostasis.

Plasma membrane

The outer boundary of a cell that regulates the passage of substances in and out, providing structural support and protection.

Concentration gradient

The difference in the concentration of a substance across a distance, influencing the movement of molecules during processes such as diffusion.

Phospholipids

The primary components of cell membranes, consisting of a hydrophilic head and two hydrophobic tails, which arrange themselves in a bilayer.

Concentration gradient

A concentration gradient occurs when there is a difference in the concentration of a substance in two different areas, causing molecules to move from an area of higher concentration to an area of lower concentration.

Cytoplasm

The gel-like substance within a cell, surrounded by the cell membrane, where organelles are suspended and various cellular processes occur.

Cytosol

The fluid portion of the cytoplasm, excluding organelles and other insoluble components, where metabolic activities take place.

Inclusions

Substances temporarily stored in the cytoplasm, such as nutrients, pigments, and other materials that cells may utilize.

Nucleus

The membrane-bound organelle that contains the cell's genetic material (DNA) and controls cellular activities, including gene expression and replication.

Nuclear envelope

The double membrane structure that surrounds the nucleus, separating its contents from the cytoplasm and regulating the passage of materials in and out of the nucleus.

Nuclear pore

A protein-lined channel in the nuclear envelope that regulates the exchange of substances, such as RNA and proteins, between the nucleus and the cytoplasm.

Chromosomes

Structures made of DNA and proteins that carry genetic information. They become visible during cell division when the DNA condenses.

Chromatin

The complex of DNA and proteins found in the nucleus, existing in a less condensed form than chromosomes, and responsible for packaging the genetic material.

Nucleolus

A small, dense region within the nucleus where ribosomal RNA (rRNA) is synthesized and ribosome assembly begins.

DNA (deoxyribonucleic acid)

The molecule that carries the genetic instructions for life, consisting of two strands that form a double helix structure, made of nucleotides.

RNA (ribonucleic acid)

A molecule involved in various biological roles, including coding, decoding, regulation, and expression of genes, typically single-stranded and made of ribonucleotides.

Ribosomes

Cellular structures that synthesize proteins by translating messenger RNA (mRNA) into polypeptide chains. They can be found free-floating in the cytoplasm or attached to the endoplasmic reticulum.

Proteins

Large, complex molecules made up of amino acids that perform a wide range of functions in the body, including catalyzing biochemical reactions, facilitating cell signaling, and providing structural support.

Nucleolus

A prominent substructure within the nucleus of eukaryotic cells, responsible for ribosomal RNA (rRNA) synthesis and ribosome assembly.

Free ribosomes

Ribosomes that float freely in the cytoplasm, synthesizing proteins that function within the cell.

Fixed ribosomes

Ribosomes that are attached to the endoplasmic reticulum, synthesizing proteins intended for secretion or incorporation into membranes.

Enzymes

Biological catalysts that speed up chemical reactions in the body by lowering the activation energy required.

Endomembrane system

A series of membranes within the cell that create compartments for various functions, including the endoplasmic reticulum, Golgi apparatus, and lysosomes.

Vesicles

Small membrane-bound sacs that transport materials within the cell, often between the endoplasmic reticulum and the Golgi apparatus.

Smooth endoplasmic reticulum

A type of endoplasmic reticulum that lacks ribosomes and is involved in lipid synthesis, metabolism, and detoxification.

Rough endoplasmic reticulum

A type of endoplasmic reticulum studded with ribosomes, primarily involved in protein synthesis and modification.

Golgi apparatus

An organelle that modifies, sorts, and packages proteins and lipids for secretion or delivery to other organelles.

Lysosome

A membrane-bound organelle containing digestive enzymes that break down waste materials and cellular debris.

Mitochondria

Membrane-bound organelles known as the powerhouses of the cell, responsible for producing ATP through cellular respiration.

ATP (adenosine tri-phosphate)

An energy-carrying molecule found in the cells of all living organisms, ATP stores and provides energy for various cellular processes.

Cristae

Internal folds of the mitochondria that increase the surface area for energy production.

Mitochondrial matrix

The space within the inner membrane of the mitochondria, containing enzymes, mitochondrial DNA, and ribosomes for ATP production.

Cytoskeleton

A network of protein filaments and tubules that provide structural support, shape, and facilitate cell movement.

Motor proteins

Specialized proteins that interact with the cytoskeleton to facilitate movement within cells, such as transport of organelles and muscle contraction.

Microvilli

Finger-like projections on cell surfaces that increase surface area for absorption and secretion.

Cilia

Hair-like structures that extend from the surface of some eukaryotic cells, facilitating movement and fluid flow.

Flagella

Long, whip-like structures that extend from the surface of some cells, enabling locomotion and fluid movement.