PHYSIO EXAM 1: part 1

What is the fundamental unit of homeostasis?

The cell.

What is the primary function of the plasma membrane?

It selectively regulates movement of ions, nutrients, and wastes while supporting communication and signal transduction.

What is the plasma membrane structurally composed of?

A phospholipid bilayer embedded with functional proteins.

What does the plasma membrane maintain inside the cell?

A distinct intracellular chemical composition.

What is the nucleus?

The repository of genetic information enclosed by a double-layered nuclear envelope.

What do nuclear pores regulate?

Transit of RNA and proteins between the nucleus and cytoplasm.

What is the nucleolus responsible for?

Manufacturing ribosome components.

What is chromatin?

A network of DNA and associated proteins in the nucleus.

What is the primary role of mitochondria?

Energy transfer: converting nutrient chemical bonds into ATP.

What does cellular respiration consume and produce?

Consumes O₂; produces CO₂, heat, and water.

What are the major structural regions of a mitochondrion?

Outer membrane, inner membrane with cristae, and matrix.

What are cristae?

Folds of the inner mitochondrial membrane extending into the matrix.

Which pathways does the mitochondrial matrix host according to the guide?

The Krebs cycle and fatty acid oxidation; it also shares parts of the urea cycle and gluconeogenesis.

What are ribosomes made of?

RNA and protein.

What do free ribosomes synthesize?

Cytosolic proteins.

What do ribosomes bound to rough ER produce?

Proteins destined for secretion or organelle distribution.

What distinguishes rough ER from smooth ER?

Rough ER has attached ribosomes; smooth ER lacks attached ribosomes.

What is the primary role of rough ER in this guide?

Packaging proteins for the Golgi apparatus.

What does smooth ER synthesize?

Lipids and carbohydrates.

What else does smooth ER do besides synthesis?

Detoxifies hydrophobic molecules and stores/releases Ca²⁺.

Why is smooth-ER Ca²⁺ storage important?

Ca²⁺ regulates activities such as muscle contraction.

What is the Golgi apparatus structurally?

Cup-shaped, flattened membranous sacs.

What does the Golgi apparatus do?

Modifies, sorts, and packages proteins arriving from rough ER into secretory vesicles.

What are examples of Golgi modifications?

Formation of glycoproteins and glycolipids.

What are lysosomes?

Acidic, single-membrane organelles containing digestive enzymes.

What do lysosomes degrade?

Complex macromolecules, bacteria, and damaged organelles.

What are peroxisomes?

Dense oval organelles that use molecular oxygen to remove hydrogen from organic molecules.

What byproduct is generated during peroxisomal oxidation?

H₂O₂, which peroxisomes also break down.

What molecules are targeted by peroxisomal oxidation in the guide?

Lipids and alcohol.

What is an essential peroxisomal metabolic function?

Fatty-acid beta-oxidation into two-carbon fragments for ATP production.

What is the cytoskeleton?

A dynamic filamentous network that maintains cell shape and facilitates movement.

What is the subunit of actin filaments?

G-actin.

What is the diameter of actin filaments?

7 nm.

What are major actin filament functions?

Cell shape, amoeboid movement, cell division, and muscle contraction.

What proteins form intermediate filaments?

Keratin, desmin, and lamin.

What is the diameter of intermediate filaments?

10 nm.

What are major intermediate-filament functions?

Mechanical strength, nuclear anchoring, and resistance to mechanical stress.

What is the subunit of microtubules?

Tubulin.

What is the diameter of microtubules?

25 nm.

What are major microtubule functions?

Provide rigid framework for neuronal processes and tracks for organelle movement.

What are cilia?

Hair-like surface extensions with a microtubule core that propel substances.

What is an example of cilia function?

Moving mucus in the trachea against gravity.

What do centrosomes do?

Regulate microtubule formation and generate spindle fibers during cell division.

Why are spindle fibers important?

They ensure accurate chromosome separation during cell division.

What is a gene?

A portion of DNA containing the sequence that codes for a specific protein.

What is the genome?

The total genetic information stored within the DNA of an entire cell.

What are chromosomes?

Tightly condensed bodies formed by DNA and histone proteins.

What are histones?

Proteins that facilitate coiling of DNA.

What is a nucleosome?

The structural unit formed by DNA coiling around histones.

Where does transcription occur?

In the nucleus.

What is the product of transcription?

A new messenger RNA (mRNA) molecule.

What enzyme binds the promoter to begin transcription?

RNA polymerase.

What is a promoter?

The start region of a gene where RNA polymerase binds.

How can different cell types produce different proteins?

Promoters can be blocked or made available, regulating which genes are expressed.

What is the template strand used for during transcription?

RNA polymerase uses it to synthesize the primary RNA transcript.

What do spliceosomes do?

Remove introns and join exons during mRNA maturation.

What are introns?

Non-coding regions removed from the primary RNA transcript.

What are exons?

Coding regions joined to form functional mRNA.

Where does translation occur?

In the cytoplasm.

What is the role of mRNA in translation?

It serves as the template for protein assembly.

What happens during translation initiation?

The ribosome assembles at the start codon and the first tRNA carrying methionine binds.

What happens during translation elongation?

tRNA anticodons match mRNA codons and deliver amino acids to the growing polypeptide.

What happens during translation termination?

A stop codon is reached and the completed protein is released.

What regulates gene expression according to the guide?

Transcription factors and the preinitiation complex.

What is ubiquitin tagging?

Tagging proteins destined for destruction with ubiquitin.

What does the proteasome do?

Degrades proteins tagged with ubiquitin.

Why is ubiquitin-proteasome degradation important?

It prevents accumulation of defective proteins.

What is metabolism?

The sum of all chemical reactions in the cell.

What is catabolism?

Energy-releasing breakdown of molecules.

What is anabolism?

Energy-consuming synthesis of molecules.

What do enzymes do?

Lower the activation energy required for reactions.

Where does an enzyme-substrate complex form?

At the enzyme's active site.

What factors strictly limit reaction rates according to the guide?

Substrate concentration, enzyme concentration, temperature, and presence of catalysts.

Where does glycolysis occur?

In the cytosol.

What does glycolysis do?

Breaks down glucose to pyruvate under anaerobic or aerobic conditions.

Which other pathways have portions in the cytosol?

The urea cycle and gluconeogenesis.

Where does the Krebs cycle occur?

In the mitochondrial matrix.

What does the Krebs cycle generate/release?

Generates Acetyl CoA and releases electrons.

Which other pathways have portions in the mitochondrial matrix?

The urea cycle and gluconeogenesis.

Where is the electron transport chain located?

On the inner mitochondrial membrane (cristae).

What happens at the electron transport chain?

Oxidative phosphorylation produces most cellular ATP while O₂ is consumed.

What does smooth ER use the cytochrome P450 system for?

Detoxification/metabolism of hydrophobic molecules.

What is CYP3A4?

A primary cytochrome P450 enzyme involved in smooth-ER drug metabolism.

How can grapefruit juice affect CYP3A4?

Its substances can inhibit CYP3A4.

What can CYP3A4 inhibition do to susceptible medications?

Prevent their breakdown and increase drug levels.

What clinical risk is highlighted with statins?

Elevated levels can increase risk of statin-induced rhabdomyolysis, severe muscle damage.

What are nutritional raw materials for metabolism listed in the guide?

Water, minerals, essential amino acids, and fatty acids.

How are vitamins classified?

As water-soluble or fat-soluble.

What role do vitamins play in metabolism?

They act as essential cofactors in metabolic pathways.

What is passive transport?

Movement down a concentration gradient without ATP.

What is simple diffusion?

Direct movement of lipid-soluble molecules through the phospholipid bilayer.

What is facilitated diffusion?

Movement through a membrane carrier that changes shape to transport a molecule.

What is primary active transport?

Transport that directly uses ATP to move substances against a gradient.

What is secondary active transport?

Transport powered by electrochemical gradients established by primary transport.

What does Na⁺/K⁺-ATPase do per ATP?

Pumps 3 Na⁺ out and 2 K⁺ in.

Why is Na⁺/K⁺-ATPase important?

It helps maintain cell volume and electrical potential.

How does Na⁺/K⁺-ATPase help prevent cell swelling?

Its ion movement prevents osmotic water influx that could cause swelling and lysis.

What can happen to cells in hypotonic environments without adequate Na⁺/K⁺-ATPase activity?

Water influx can cause cell swelling and lysis.

What do ion channels do?

Allow specific ions to pass and are fundamental for nerve impulse transmission.

What do membrane carriers do?

Bind substances and change conformation to facilitate transport.