Cellular Level of Organization - Flashcards

A set of Q&A flashcards covering cellular structure, organelles, membrane transport, protein synthesis, and the cell cycle based on lecture notes.

What are the three tenets of the cell theory?

1) Cells are the building blocks of all plants and animals. 2) All new cells come from division of preexisting cells. 3) Cells are the smallest unit that perform all vital physiological functions.

What is extracellular fluid (ECF)?

The watery medium surrounding cells; interstitial fluid in most tissues.

What is the primary function of the plasma membrane?

A selectively permeable membrane that controls entry of ions and nutrients, elimination of wastes, and release of secretions.

What is the glycocalyx and what are its functions?

A carbohydrate layer on the outer surface of the cell membrane composed of proteoglycans, glycoproteins, and glycolipids; functions in cell recognition, binding to extracellular structures, and lubrication.

What is the difference between integral and peripheral membrane proteins?

Integral proteins span the membrane and cannot be removed without damage; peripheral proteins are attached to the membrane surface and are removable.

What are microvilli and their role?

Finger-shaped extensions of the plasma membrane with a core of microfilaments that increase surface area for absorption.

Name the three components of the cytoskeleton and their typical diameters.

Microfilaments (<6 nm), Intermediate filaments (7–11 nm), Microtubules (~25 nm).

What are centrioles and why are they important for cell division?

Cylindrical microtubule structures (9 triplets each) in centrosomes; they organize spindle apparatus and DNA movement during division; cells without centrioles cannot divide.

Describe cilia and basal bodies.

Cilia are long, slender extensions with nine groups of microtubule triplets around a central pair; basal bodies anchor cilia to the cell surface and organize the axoneme.

What are ribosomes and where are they located?

Ribosomes are two-subunit organelles (small and large) made of protein and rRNA; they synthesize proteins. Free ribosomes are in the cytosol; bound ribosomes are attached to the rough ER.

What are the two types of endoplasmic reticulum and their roles?

Smooth ER (SER) lacks ribosomes and synthesizes lipids and carbohydrates; Rough ER (RER) has fixed ribosomes and modifies proteins destined for secretion or Golgi transport.

What are the main functions of the Golgi apparatus?

Modifies, sorts, and packages proteins for secretion or delivery to specific destinations; renews or modifies the plasma membrane; packages enzymes for cytosol and lysosomes.

What are lysosomes and why are they called 'suicide packets'?

Membrane-bound vesicles containing digestive enzymes; involved in autolysis and breaking down cellular waste; can cause cell damage if membranes rupture.

What is the mitochondrion and its role in energy production?

A double-m membrane organelle with cristae and matrix that produces ATP via glycolysis (cytosol) and oxidative phosphorylation; mitochondria are abundant in energy-demanding cells.

What is the nucleus and its major components?

Usually the largest cellular structure that houses DNA and coordinates cellular activities; contains nucleolus (RNA synthesis) and nucleoplasm.

What is DNA and the basic genetic code concept?

DNA is composed of nucleotides with A, T, C, G bases; a gene is the functional unit encoding a specific protein; a triplet codon on mRNA specifies an amino acid.

What happens during gene activation and transcription?

Histones are removed to uncoil DNA; RNA polymerase binds to the promoter and synthesizes an mRNA strand complementary to DNA.

Outline the steps of transcription.

1) Gene activation; 2) RNA polymerase binds to promoter; 3) mRNA is synthesized (pre-mRNA); 4) Immature mRNA is processed; introns are removed and exons joined to form mature mRNA; mRNA exits the nucleus.

What occurs during translation?

mRNA binds to the small ribosomal subunit; tRNA brings amino acids; large subunit joins; peptide bonds form; stop codon ends translation and ribosomal subunits detach.

What is the role of mRNA processing in translation?

Introns are removed and exons are spliced together to form mature mRNA before exiting the nucleus.

Differentiate diffusion and osmosis and list factors affecting diffusion rates.

Diffusion: movement of solutes down a concentration gradient; osmosis: diffusion of water across a membrane. Rates depend on distance, size of molecule, temperature, gradient size, and electrical charges.

What is osmosis and osmotic pressure?

Osmosis is net water diffusion across a selectively permeable membrane; osmotic pressure is the force driving water movement into a solution with higher solute concentration.

Define tonicity and the three tonicity scenarios.

Tonicity is the effect of osmotic solutions on cell volume. Isotonic: no net water movement; hypotonic: water into cell causing swelling/hemolysis; hypertonic: water out causing crenation.

What is carrier-mediated transport and its three types?

Hydrophilic or large molecules transported by carrier proteins. Types: Facilitated diffusion (no ATP, saturable), Active transport (requires ATP, moves against gradient, e.g., Na+/K+ ATPase), Secondary active transport (indirect ATP use).

Explain vesicular transport and its two main forms.

Movement of materials in vesicles requiring ATP. Types: Endocytosis (receptor-mediated endocytosis, pinocytosis, phagocytosis) and Exocytosis.

What are the phases of mitosis and the key events in each?

Prophase: chromosomes condense, nuclear envelope breaks; Metaphase: chromosomes align at plate; Anaphase: chromatids separate; Telophase: nuclei form and cytokinesis begins (cleavage furrow).

What is interphase and the phases G0, G1, S, and G2?

G0: resting/normal function; G1: growth and organelle duplication; S: DNA replication; G2: final protein synthesis and centriole replication; interphase is the cell’s non-dividing period.

What is cancer, and the difference between benign and malignant tumors with metastasis?

Cancer involves mutations that disrupt normal cell division. Benign tumors remain in original tissue; malignant tumors grow, invade, and metastasize to form secondary tumors.