Human Cell Structure & Function: Organelles, Membranes, and Cytoskeleton

Human Cells

Smallest living structural & functional unit of the human body.

Cell Division

Process by which cells reproduce.

Organelles

Specialized structural & functional units within a cell.

Extracellular Fluid

Fluid surrounding the cells that facilitates exchange.

Basic Animal Cell Type

Eukaryotic cell structure including nucleus, plasma membrane, cytoplasm, organelles, cytosol, and inclusions.

Nucleus

Contains DNA and is surrounded by a double nuclear membrane with pores.

Nuclear Membrane

Double membrane with pores allowing large molecules to move inside.

DNA

Genetic material housed within the nucleus.

Multinucleate

Cells that contain more than one nucleus.

Anucleate

Cells that do not contain a nucleus.

Nucleoplasm

Substance within the nucleus.

Nucleolus

Organelle in nucleus that assembles ribosomes.

Chromatin

Loose DNA form involved in protein synthesis.

Chromosomes

Dense, rodlike DNA structures involved in cell division.

Nuclear Pores

Structures that allow the exchange of materials between the nucleus and cytoplasm.

Plasma Membrane

Selectively permeable barrier that regulates exchange with extracellular fluid.

Phospholipid Bilayer

Basic structure of the plasma membrane composed of lipids and proteins.

Glycocalyx

Carbohydrate structure on the cell membrane that contributes to cellular recognition.

Cytoplasm

Material between the plasma membrane and nucleus.

Cytosol

Intracellular fluid component of the cytoplasm.

Inclusions

Temporarily stored substances within the cytoplasm.

Endoplasmic Reticulum

Organelle involved in lipid synthesis and protein synthesis.

Golgi Apparatus

Structure that modifies, packages, and sorts proteins for secretion.

Lysosomes

Vesicles filled with digestive enzymes for intracellular digestion.

Peroxisomes

Membranous sacs of enzymes that detoxify harmful substances.

Mitochondria

Double membrane organelle responsible for ATP synthesis.

Outer mitochondrial membrane

The membrane surrounding the mitochondrion, involved in energy synthesis.

Function of Mitochondria

Produce ATP by cellular respiration for energy needs of the cell; called the 'powerhouse' of the cell.

Ribosomes

Non-membranous structures composed of two subunits that are involved in protein synthesis.

Free ribosomes

Ribosomes that synthesize proteins for intracellular use.

Fixed ribosomes

Ribosomes that synthesize proteins destined for secretion, or incorporation into lysosomes, plasma membrane, or cell membranes.

Cytoskeleton

A non-membranous network of protein structures that acts as the cell's 'muscles & bones', determines cell shape, supports organelles, and is involved in internal transport & cellular movements.

Centrosome

The 'cell center' that is closely adjacent to the nucleus, builds microtubules in non-dividing cells, and forms the mitotic spindle during cell division.

Centrioles

Paired perpendicular bodies in the centrosome that assist in spindle formation.

Cilia

Short, numerous motile projections of the cell surface that move substances over free surfaces.

Flagella

Long, singular motile projections that propel human sperm cells.

Microvilli

Microscopic projections of the plasma membrane that increase the surface area of the cell.

Goblet cell

A cell that secretes mucin, forming a layer of mucus.

Phagocytosis

A process where a lysosome fuses with an incoming phagocytic vesicle to enable digestion.

Endoplasmic Reticulum (ER)

A network of membranous tubules and sacs; SER handles lipid synthesis and detox; RER handles protein synthesis with ribosomes.

Lysosome

An organelle involved in intracellular digestion and autophagy.

Peroxisome

An organelle involved in detoxification and lipid metabolism, managing hydrogen peroxide.

Mitochondrion

An organelle that produces ATP via oxidative phosphorylation and contains its own DNA.

Centrosome/Centrioles

Organizers of the spindle apparatus for cell division.

Cilia/Flagella

Motile surface projections; microvilli increase surface area.