Cell Structure and Function

Features of Eukaryotic Cells

• Basic structural unit of an organism.
• Usually microscopic.
• Enclosed by a semipermeable membrane.
• Eukaryotic cells contain a nucleus to hold genetic material.
• Many cells are specialized and function with others in multicellular organisms.

Cell Membrane

• Gives shape and protection to the cell.
• Controls what enters and exits the cell.
• Communicates and responds to the environment.

Cytoplasm and Cytosol

• Cytoplasm: contents of the cell (excluding the cell membrane and nucleus).
  • Contains fluid and cell organelles.
• Cytosol: the fluid portion of the cytoplasm.

Cell Nucleus

• Contains DNA.
• Helps to control cellular events.

Ribosomes

• Small structures in the cytoplasm (made of protein and RNA).
• Help to synthesize proteins.
  • Free ribosomes produce proteins for intracellular use.
  • Attached ribosomes produce proteins for extracellular use.

Endoplasmic Reticulum

• Rough Endoplasmic Reticulum (RER): synthesizes proteins transported to the Golgi complex.
• Smooth Endoplasmic Reticulum (SER): manufactures lipids sent to the Golgi complex.

Golgi Body

• Receives proteins from RER and lipids from SER.
• Packages these into secretory vesicles for secretion.

Lysosomes

• Contain enzymes for digesting unwanted cellular materials (e.g., damaged organelles, bacteria).

Mitochondria

• Main site for energy release from food molecules (using oxygen).
• Energy is stored in adenosine triphosphate (ATP).

Cytoskeleton

• Network of protein filaments in the cytosol.
  • Microfilaments: solid fibers used as cell "scaffolding."
  • Microtubules: used in cellular transport and cell division.

Cell Membrane Structures

• Microvilli: finger-like projections that increase the surface area of the cell, aiding secretion and absorption.
• Flagellum: tail-like structure for locomotion (e.g., sperm cells).
• Cilia: tiny, hair-like extensions that move materials across cell surfaces.