Structure and Function of the Eukaryotic Animal Cell

Animal Cell Structure

Overview of the Eukaryotic Animal Cell

The animal cell is a fundamental unit of life in multicellular organisms, characterized by a complex internal structure with specialized organelles. Each organelle performs distinct functions necessary for cellular survival, growth, and communication.

• Cell Membrane: The outer boundary of the cell, composed of a phospholipid bilayer with embedded proteins. It regulates the movement of substances in and out of the cell and facilitates cell signaling.

• Cytoplasm: The gel-like substance within the cell membrane, containing organelles and cytosol. It provides a medium for metabolic reactions.

Nucleus

The nucleus is the control center of the cell, containing genetic material and directing cellular activities.

• Nuclear Envelope: Double membrane that surrounds the nucleus, separating it from the cytoplasm.

• Nucleolus: Dense region within the nucleus responsible for ribosome synthesis.

• Chromatin: DNA and associated proteins that carry genetic information.

Endoplasmic Reticulum (ER)

The endoplasmic reticulum is a network of membranes involved in protein and lipid synthesis.

• Rough ER: Studded with ribosomes; synthesizes and processes proteins.

• Smooth ER: Lacks ribosomes; involved in lipid synthesis and detoxification.

Golgi Apparatus

The Golgi apparatus modifies, sorts, and packages proteins and lipids for secretion or delivery to other organelles.

• Cisternae: Flattened membrane sacs that process and transport cellular products.

Mitochondria

Mitochondria are the powerhouses of the cell, generating energy through cellular respiration.

• Function: Convert glucose and oxygen into ATP, the cell's energy currency.

• Structure: Double membrane with inner folds called cristae to increase surface area for energy production.

• Equation for Cellular Respiration: $C_6H_{12}O_6 + 6O_2 \rightarrow 6CO_2 + 6H_2O + ATP$

Lysosomes

Lysosomes are membrane-bound organelles containing digestive enzymes.

• Function: Break down waste materials, cellular debris, and foreign substances.

Ribosomes

Ribosomes are the sites of protein synthesis, found either free in the cytoplasm or attached to the rough ER.

• Function: Translate messenger RNA (mRNA) into polypeptide chains.

Cytoskeleton

The cytoskeleton provides structural support, maintains cell shape, and facilitates movement.

• Microtubules: Hollow tubes that help with cell division and intracellular transport.

• Microfilaments: Thin fibers involved in cell movement and shape changes.

• Intermediate Filaments: Provide mechanical strength to the cell.

Centrioles

Centrioles are cylindrical structures involved in organizing microtubules during cell division.

• Function: Help form the mitotic spindle during mitosis.

Comparison Table: Major Animal Cell Organelles

Organelle	Main Function	Structure
Nucleus	Genetic control	Double membrane, nucleolus
Mitochondria	Energy production	Double membrane, cristae
Golgi Apparatus	Protein/lipid modification	Stacked cisternae
ER (Rough/Smooth)	Protein/lipid synthesis	Membranous network
Lysosome	Digestion	Membrane-bound vesicle
Ribosome	Protein synthesis	RNA/protein complex
Cytoskeleton	Support/movement	Protein filaments
Centrioles	Cell division	Cylindrical microtubules

Example: Cellular Respiration in Mitochondria

During cellular respiration, mitochondria convert glucose and oxygen into ATP, which powers cellular activities such as muscle contraction and nerve impulse transmission.

Additional info: This study guide is based on a model image of an animal cell, with organelles identified and described according to standard anatomy and physiology curriculum.