Cell Theory (Bio MCAT) Flashcards

Cell Theory

• All living organisms consist of cells.
• Cells are the basic structural and functional units of life.
• New cells arise only from pre-existing cells through division.
• Cells carry genetic information as DNA, transmitted from parent to daughter cells.

Eukaryotic Cells

• Possess membrane-bound organelles for compartmentalization, enhancing specialization of cellular functions.

Nucleus

• Houses genetic material essential for cell replication.
• Enclosed by a nuclear membrane, separating it from the cytoplasm.
• Contains nuclear pores for selective exchange between the cytoplasm and nucleus.

Nucleolus

• Site of ribosomal RNA (rRNA) synthesis within the nucleus.

Genes

• Defined as coding regions within DNA that direct the synthesis of proteins.

Mitochondria

• Surrounded by an outer membrane acting as a barrier and an inner membrane folded into cristae, housing enzymes for the electron transport chain.
• Contains intermembrane space and mitochondrial matrix.
• Replicate independently via binary fission, possessing their own genetic material.

Lysosomes

• Contain hydrolytic enzymes for breaking down various substrates.
• Work with endosomes to transport and sort cellular materials.

Endoplasmic Reticulum (ER)

• A membrane system aiding in protein and lipid production, processing, and transport.

Rough Endoplasmic Reticulum (RER)

• Studded with ribosomes, responsible for assembling proteins for transport.
• Directly translates proteins destined for secretion into its lumen.

Smooth Endoplasmic Reticulum (SER)

• Lacks ribosomes; synthesizes lipids, regulates calcium levels, and detoxifies substances.
• Transports proteins from RER to the Golgi apparatus.

Golgi Apparatus

• Membrane system that modifies and packages proteins for cellular export.

Cytoskeleton

• Provides structural support and maintains cellular shape.
• Facilitates transport within the cell through three components: microfilaments, microtubules, and intermediate filaments.

Microtubules

• Hollow rods made of tubulin proteins; key for cell shape and movement.
• Serve as tracks for motor proteins like kinesin and dynein to transport vesicles.

Microfilaments

• Composed of actin, forming networks that resist compression and fracture.
• Involved in muscle contraction and cytokinesis through their interaction with myosin.

Intermediate Filaments

• Made of various filamentous proteins (keratin, desmin, vimentin, lamins).
• Provide rigidity, help with cell adhesion, and anchor organelles.

Peroxisomes

• Contain enzymes that produce and degrade hydrogen peroxide.
• Break down long-chain fatty acids via beta-oxidation and participate in phospholipid synthesis.

Viruses

• Classified as non-living because they cannot reproduce independently and often contain RNA as their genetic material.

Importance of Membrane-Bound Organelles

• Compartmentalization allows for distinct cellular functions and processes.
• Organelle membranes are primarily composed of a phospholipid bilayer.