Biology review

Organelles Cheat Sheet

Introduction to Organelles

• Organelles are often best learned through "Grouping" based on their functions and locations within the cell.

• Eukaryotic cells contain a true nucleus, while prokaryotic cells do not have a nucleus.

  • Examples of Eukaryotic Cells: Animal cells, Plant cells.

  • Examples of Prokaryotic Cells: Bacteria.

• Plant cells possess a cell wall and chloroplasts, which contain chlorophyll, while animal cells do not possess either of these structures.

Grouping and Definitions of Organelles

Nucleus and Associated Structures

• Nucleus:

  • Functions as the control center of the cell regulating various cellular activities.

  • Responsible for storing and protecting DNA and genetic information.

• Nuclear Envelope:

  • A double membrane encasing the nucleus.

  • Contains tiny pores that facilitate the movement of molecules in and out of the nucleus.

• Nucleolus:

  • The largest structure within the nucleus of eukaryotic cells.

  • Primary site for ribosome synthesis.

• Nucleoplasm:

  • Similar to cytosol but is specific to the nucleus.

• Ribosomes:

  • Responsible for synthesizing proteins.

  • Can be found free in the cytosol or bound to the Endoplasmic Reticulum (ER).

Protein Traffic and Metabolic Function

The Endomembrane System

• Functions similarly to an organ system with various organelles necessary for the creation, transport, and detoxification of materials within the cell.

• Endoplasmic Reticulum (ER):

  • Extensive network of membranes continuous with the nucleus.

  • Composed of two main regions:

  • Rough ER:

  • Contains ribosomes attached to its surface; where protein synthesis occurs via bound ribosomes.

  • Smooth ER:

  • Lacks ribosomes.

  • Functions include:

    • Synthesis of lipids

    • Metabolism of carbohydrates

    • Calcium storage

    • Detoxification of drugs and proteins.

• Golgi Apparatus:

  • Functions as the 'shipping' part of the cell.

  • Receives, sorts, ships, and manufactures products from the ER.

  • Extensively networked for efficient transport and modifies:

  • Proteins

  • Carbohydrates on proteins

  • Phospholipids

  • Synthesis of polysaccharides.

• Lysosomes:

  • Membranous sac containing hydrolytic enzymes responsible for digesting macromolecules.

  • Care must be taken to prevent the release of these enzymes into the cytosol, as they can potentially harm the cell.

• Vesicles:

  • Membrane-bound containers, such as vacuoles.

• Vacuoles:

  • Large vesicles derived from the Golgi apparatus and ER.

  • Selectively transport solutes.

  • Example: Contractile vacuoles pump excess water out of the cell, maintaining homeostasis.

  • In plants, vacuoles serve dual roles as storage units for proteins and organic compounds, specifically the central vacuole stores potassium, chloride, and inorganic compounds.

  • They expand with cell growth allowing for maintained cytoplasmic volume.

Organelles Involved in Energy Transformation

• Mitochondrion:

  • Double-membrane organelle involved in cellular respiration, producing ATP (adenosine triphosphate).

  • Known as the powerhouse of the cell.

  • Features inner membrane folds called cristae.

• Chloroplasts:

  • Organelles specific to plant cells with double membranes.

  • Contain thylakoids, essential for photosynthesis.

• Peroxisomes:

  • Similar to lysosomes but primarily involved in using oxygen to break down fatty acids for transport to mitochondria for energy conversion.

  • Produces hydrogen peroxide as a byproduct.

Cytoskeleton

• The cytoskeleton provides structural support and motility to the cell.

• Composed of fibers enhancing the cellular framework.

Cell Theory

• Fundamental biological principle stating three key tenets:

  • Living organisms are composed of cells.

  • Cells are the basic structural and organizational unit of all organisms.

  • All cells arise from pre-existing cells.