Cell Biology: Cytoplasm and Organelles

Cytoplasm

• Material between plasma membrane and nucleus
• Cytosol: solution where cellular materials are suspended
• Organelles: structures within the cell, have specialized functions
• Inclusions: various chemical substances

Cytoplasmic Organelles

• Membranous: Mitochondria, Endoplasmic reticulum, Golgi apparatus, Peroxisomes, Lysosomes
• Nonmembranous: Ribosomes, Cytoskeleton, Centrioles
• Membranes allow compartmentalizing, independent environment

Mitochondria

• Provides energy to the cell through ATP
• Aerobic cell respiration
• Glucose + Oxygen: Complex process
• Double membrane, contains cristae
• Cristae increase surface area
• Inner membrane contains proteins, outer is smooth
• Matrix: inner section
• Contains its own DNA and RNA
• Resembles bacterial cell
• Possible evolutionary symbiosis
• Fission: able to multiply when energy requirements increase

Ribosomes

• Nonmembranous organelles
• Site of protein synthesis
• Composed of protein and ribosomal RNA (rRNA)

Peroxisomes

• Membranous sacs, contain detoxifying substances to neutralize toxins
• Free radicals: toxic, highly reactive molecules, byproducts of metabolism
• Also play a role in the breakdown and synthesis of fatty acids

Lysosomes

• Membranous structures containing digestive enzymes (acid hydrolases)
• Digestion process works best in acidic conditions
• Digest ingested bacteria, viruses, and toxins
• Degrades organelles
• Metabolic functions: break down and release glycogen; break down and release Ca2+ from bone
• Autolysis: cell digests itself

Endomembrane System

• Consists of membranous organelles: ER, Golgi Apparatus, secretory vesicles, lysosomes, nuclear and plasma membranes.
• Work together to produce, degrade, store, and export molecules

Centrioles

• Centrosomes are located near the nucleus
• Microtubule organizing center
• Newly assembled microtubules radiate from the centrosome to the rest of the cell
• Some microtubules aid in cell division, while others form a cytoskeletal track system
• Centrioles also form the basis of cilia and flagella

Cilia

• Whiplike motile extensions on the surface of certain cells (e.g. respiratory cells)
• Movement of cilia can move substances across a surface (e.g. mucus).
• Made up of microtubules synthesized by centrioles: basal bodies

Flagella

• Longer extensions that propel the whole cell (e.g., tail of sperm)
• Made up of microtubules synthesized by centrioles: basal bodies.

Microvilli

• Minute, fingerlike extensions of the plasma membrane that project from the surface of select cells (e.g. intestinal and kidney tubule cells).
• Used to increase surface area for absorption
• Made up of actin microfilaments for stiffening projections.

Nucleus

• Largest organelle; contains the genetic library of blueprints for the synthesis of almost all cellular proteins
• Responds to signals that dictate the type and amount of proteins needed to be synthesized
• Most cells are uninucleate (one nucleus)
• Some cells are multinucleate or anucleate

Nuclear Envelope

• Double membrane barrier that encloses the nucleoplasm
• Outer layer: continuous with the rough ER, has ribosomes.
• Inner layer: nuclear lamina, network of proteins that maintains nuclear shape and acts as scaffolding for DNA
• Nuclear pores allow substances to pass into and out of the nucleus
• Nuclear pore complexes regulate the movement of substances.

Explore the essential components of the cytoplasm and the various organelles involved in cellular functions. This quiz covers key aspects of organelles like mitochondria and ribosomes, their structures, and their roles in the cell. Test your knowledge on these fundamental topics in cell biology.