anatomy exam 1 chapter 3

What do the prefix "cyto-" and the suffix "-cyte" indicate in anatomical terminology?

"cyto-" = relationship to a cell or cellular fluid (e.g., cytoplasm, cytosol)

"-cyte" = a specific mature cell type (e.g., osteocyte)

What are the 3 basic structural parts common to human cells?

1) Plasma membrane (outermost selectively permeable boundary).

2) Cytoplasm (intracellular fluid containing organelles).

3) Nucleus (cellular control center containing DNA).

Which major blood cell type lacks a nucleus, and what is the functional consequence of this feature?

Red blood cells (erythrocytes) lack a nucleus, meaning they cannot synthesize new proteins or undergo mitotic cell division.

What basic functional separation is created by the plasma membrane?

it separates the intracellular fluid (ICF) inside the cell from the extracellular fluid (ECF) surrounding the cell.

How does the Fluid Mosaic Model describe the physical structure of the plasma membrane?

"Fluid"= thin, flexible phospholipid bilayer

"Mosaic" = various proteins randomly dispersed throughout the bilayer.

How are the phosphate heads and fatty acid tails of membrane phospholipids arranged relative to intracellular and extracellular fluids?

Polar phosphate heads are hydrophilic and face outward toward the water-based ICF and ECF. Nonpolar fatty acid tails are hydrophobic and point inward toward each other away from water.

Why can a plasma membrane easily self-repair following a small tear?

The hydrophobic fatty acid tails spontaneously rearrange and snap back together to eliminate exposure to water in the ICF and ECF.

What effect does the hydrophobic core of the phospholipid bilayer have on water-soluble and charged molecules?

acts as a physical barrier that prevents polar, water-soluble molecules and charged ions from diffusing directly across the membrane.

What is the primary function of cholesterol within the plasma membrane?

stiffens and stabilizes the membrane, reducing excessive fluidity so the membrane does not become too flimsy.

Integral proteins are..

embedded directly within the bilayer.

Transmembrane proteins are…

integral proteins that span the entire width of the membrane

Peripheral proteins are…

not embedded in the bilayer, but are loosely attached to integral proteins on the inner or outer surface

Approximately what percentage of the plasma membrane mass is composed of proteins?

50% by mass

What does it mean that transport proteins are "selective"?

a transport protein will only bind and move one or two specific chemical substances across the membrane

How do receptor proteins relay chemical messages to the interior of a cell?

Binding of a specific chemical messenger (ligand) causes the receptor protein to physically change shape, triggering internal cellular signaling

What happens to a receptor protein and cell activity after a chemical messenger unbinds?

The receptor protein returns to its original shape, and the cell returns to its baseline resting activity.

Why are cell-cell recognition proteins essential for immune system function?

WBC can distinguish invaders (viruses, bacteria, fungi) from normal “self” cells

What clinical failure occurs when cell-cell recognition proteins malfunction?

autoimmune conditions (immune cells attack the body's own healthy tissues)

How do permanent intercellular junctions differ functionally from temporary intercellular junctions?

permanent interceullular junctions= hold tissue cells firmly together to prevent tissue tearing

Temporary junctions = form and break repeatedly, allowing migrating cells to "crawl" across other cells

What is the glycocalyx and where is it located?

A protective "sugar coating" of short-branching carbohydrates attached to lipids/proteins on the extracellular membrane surface only.

what are two primary physiological functions of glycocalyx?

1. forms a barrier preventing very large substances from entering the cell

2. provides unique cell-cell identification for immune recognition

What is a tight junction, and what does it mean that tight junctions are "impermeable"?

A junction where integral proteins of neighboring cell membranes interlock and fuse together. "Impermeable" means fluids and solutes cannot pass through the space between cells.

What type of protein filament forms desmosomes, and how do desmosomes prevent tissue separation?

Cadherin filaments extend from neighboring cells and overlap like "cellular Velcro," anchoring cells together to form sheets; these sheets resist mechanical pulling and stretching forces.

what acts as “cellular velcro”?

desmosomes

Based on class worksheet material, what happens to a tissue if a mutation disrupts normal desmosome formation?

Cells lose their anchoring stickiness and separate easily when subjected to pulling or stretching forces, leading to increased tissue damage.

How do gap junctions enable direct intercellular communication?

Transmembrane proteins form channels between neighboring cells, allowing ions and small molecules to pass directly from one cell to another.

Which intercellular junction type allows electrical signals to spread rapidly between cardiac muscle cells?

gap junctions

What defines passive transport across a plasma membrane, and what is its driving force?

the movement of molecules down their concentration gradient (high to low) without requiring ATP

Force: kinetic energy of moving, colliding molecules

How do concentration gradient, molecular size, and temperature each affect diffusion speed?

1) Greater concentration difference —> faster diffusion.

2) Smaller molecular size —> faster diffusion.

3) Higher temperature —> faster diffusion.

What physical characteristics allow a substance to cross the membrane via simple diffusion?

must be small and nonpolar (lipid-soluble) to squeeze through hydrophobic fatty acid tails without transport proteins

Why can water molecules move across the plasma membrane via simple diffusion despite being polar?

because water molecules are small enough to squeeze directly between phospholipid molecules.

How does carrier-mediated facilitated diffusion transport large molecules across the membrane?

Large molecules bind to specific transmembrane carrier proteins, causing the protein to change shape and move the molecule across the membrane.

What causes a carrying capacity (transport limit) in carrier-mediated facilitated diffusion?

the limited number of binding sites

What is the difference between leaky channels and gated channels in channel-mediated facilitated diffusion?

Leaky channels are permanently open for continuous passive diffusion. Gated channels remain closed until opened by specific chemical or electrical signals.

What is osmosis?

passive diffusion of water across a selectively permeable membrane from an area of low to an area of high solute concentration

What specialized transmembrane channel protein facilitates rapid water transport during osmosis?

aquaporin

What is osmolarity, and what factor determines a solution's osmolarity?

total concentration of all solute particles in a solution. It is determined solely by the number of solute particles, not particle size or chemical type.

What is tonicity?

The ability of a solution outside the cell to change the cell’s water volume and shape by causing water to move in or out.

In an isotonic solution, in which direction does water move, and what happens to cell size?

Water moves equally in both directions across the membrane (no net water movement), and cell size and shape remain unchanged.

In a hypertonic solution, in which direction does water move, and what happens to cell size?

Water moves OUT of the cell into the solution, causing the cell to shrink and shrivel (crenate).

In a hypotonic solution, in which direction does water move, and what happens to cell size?

Water moves INTO the cell from the solution, causing the cell to swell and potentially burst (lyse).

Based on Worksheet 1, if a cell containing 10 mOsm Na⁺, 5 mOsm glucose, and 300 mOsm albumin is placed in a solution permeable only to Na⁺ and glucose, why does water enter the cell?

Na⁺ and glucose diffuse to equilibrium, but impermeable albumin remains trapped inside the cell, creating a higher internal solute concentration that draws water into the cell (hypotonic scenario)

Based on Worksheet 1, why does hyponatremia (low Na+ concentration in ECF) cause body cells and brain neurons to swell, and what tonicity IV fluid is used to treat it?

In hyponatremia, extra water dilutes the ECF, making it more watery / less concentrated, so water moves from the less concentrated ECF → more concentrated inside of the cell, causing cells to swell; a hypertonic IV fluid draws water back out.

What defines active transport across a plasma membrane?

The movement of molecules across the membrane against their concentration gradient (from low to high concentration), using atp

How does primary active transport obtain the energy needed to pump molecules?

from atp hydrolysis, where a phosphate group is transferred to the transport pump protein.

In what direction and in what exact numbers does the Na⁺-K⁺ ATPase pump move ions per ATP hydrolyzed?

It pumps 3 Na⁺ ions OUT of the cell and 2 K⁺ ions INTO the cell

What ion concentration gradients are established by the continuous activity of the Na⁺-K⁺ ATPase pump?

High Na⁺ concentration outside the cell (ECF) and high K⁺ concentration inside the cell (ICF)

How does secondary active transport move substances across the membrane, and what happens if primary active transport stops?

uses kinetic energy stored in ion gradients (established by primary active transport) to pull substances across without directly hydrolyzing ATP. If it stops, the driving gradient collapses and secondary active transport ceases.

How do phagocytosis and pinocytosis differ in what the cell engulfs and their specificity?

Phagocytosis selectively engulfs large, solid particles (e.g., bacteria) bound to receptors ("cell eating"). Pinocytosis non-specifically gulps small volumes of ECF and dissolved solutes ("cell drinking").

Why is pinocytosis functionally important to a cell if it is non-specific?

allows the cell to continuously sample the extracellular fluid to monitor its surrounding microenvironment.

What is receptor-mediated endocytosis, and what clinical vulnerability does it create?

specific target molecules bind surface receptors to form concentrated vesicles. Harmful pathogens (like flu viruses) can hijack this mechanism to invade cells.

What is exocytosis, and what cellular functions rely on it?

Vesicular transport where secretory vesicles fuse with the plasma membrane to release contents outside the cell. It is used for hormone secretion, neurotransmitter release, sweat release, and waste disposal.

What is membrane potential, and what is the typical resting membrane potential (RMP) of a human cell?

The separation of oppositely charged ions across the plasma membrane creating an electrical voltage difference. Average RMP is -70 mV (inside negative relative to outside).

What role do potassium ions (K⁺) play in establishing resting membrane potential, and why does some K⁺ remain inside the cell?

K⁺ leaks out of the cell, leaving negative proteins inside. This makes the inside negative, which pulls some K⁺ back in.

Why does sodium (Na+) have minimal direct involvement in setting the resting membrane potential?

plasma membrane is impermeable to Na+ at rest, there is also very few leaky channels of Na+.

What role does the Na⁺-K⁺ ATPase pump play in maintaining the resting membrane potential?

It keeps the ion gradients balanced by pumping Na⁺ back out and K⁺ back in when they leak across the membrane.

Based on Worksheet 3, if a neuron at rest develops double the number of leaky K⁺ channels, what happens to K⁺ movement and membrane potential?

More K⁺ leaves the cell, making the membrane potential more negative (hyperpolarized).

Based on Worksheet 3, how does doubling leaky K⁺ channels affect Na⁺-K⁺ ATPase activity?

The Na⁺-K⁺ ATPase must work harder to pump the extra K⁺ back into the cell and restore the resting membrane potential.

Based on Worksheet 3, why does hyponatremia have little to no effect on resting membrane potential?

Na+ plays almost no role in establishing resting membrane potential; K+ leak channels are primarily responsible.

What is contact signaling, and why is it important for normal tissue growth?

Direct physical contact between cell surface receptors. It regulates cell growth; when cells become tightly packed, contact signaling silences further mitotic division.

What is chemical signaling in the plasma membrane?

Binding of ligand (extracellular messenger) to a specific membrane receptor = triggers a response

What determines the specific physiological response of a cell to a ligand binding its receptor?

response is determined by the cell's internal machinery, NOT the ligand itself. The same ligand can trigger different responses in different cell types.

In a G-protein coupled receptor (GPCR) pathway, what is the ligand classified as?

the first messenger (ligand)

What happens when the ligand binds to the G protein-coupled receptor?

receptor changes shape, activates a G-protein, and the G-protein releases GDP and binds GTP to become active.

In a GPCR what happens after the G-protein becomes active?

It activates an effector enzyme, which produces 2nd messengers (Ca2+, cAMP)→ 2nd messengers activate protein kinases → kinases activate proteins → cell response.

what describes an enzyme activated by the G-protein that produces 2nd messengers?

effector enzyme