Cell Physiology and Intercellular Communications - Practice Flashcards

VOCABULARY flashcards covering cell membrane structure and function, transport, homeostasis, and intercellular communication as presented in the lecture notes.

Cell membrane

The boundary of the cell that is semi-permeable and composed mainly of proteins, phospholipids, cholesterol, and carbohydrates.

Phospholipid bilayer

The double-layer structure forming the core of the cell membrane, with hydrophilic heads and hydrophobic tails.

Hydrophilic head

The polar, water-loving part of a phospholipid.

Hydrophobic tail

The non-polar, water-hating part of a phospholipid.

Cholesterol (membrane)

A membrane component that helps stabilize membrane structure (about 13%).

Membrane proteins

Proteins making up about 55% of the membrane; perform functions such as transport, signaling, and adhesion.

Adhesion molecules

Proteins that connect cells to each other.

Enzymes (membrane)

Membrane-bound enzymes that catalyze reactions on the cell membrane.

Antigens

Surface markers (e.g., blood group antigens) on cells.

Receptors

Membrane proteins that bind signaling molecules like hormones or neurotransmitters.

Ion channels

Proteins that permit movement of ions across the cell membrane.

Carriers (facilitated diffusion)

Proteins that facilitate passive transport of larger molecules across the membrane.

Pumps (active transport)

Membrane mechanisms that move substances against their gradient using energy.

Na+/K+ pump

Primary active transport pump; exports Na+ and imports K+ using ATP (3 Na+ out, 2 K+ in).

Semi-permeable

Membrane that allows some particles to pass through and excludes others.

Osmosis

Passive movement of water from a region of low solute concentration to high solute concentration.

Simple diffusion

Passive movement of small molecules through lipid bilayer or protein channels from high to low concentration.

Facilitated diffusion

Passive movement of larger molecules via carrier proteins from high to low concentration.

Active transport

Active movement of specific ions from low to high concentration, requiring energy.

ATP

Adenosine triphosphate; energy source for active transport.

Intercellular communications

Cells communicate with one another via chemical messengers.

Gap junctions

Channels between cells that allow direct communication without entering the ECF.

Neurotransmitters

Messengers released at synaptic junctions and act across the synaptic cleft.

Synaptic cleft

The narrow space across which neurotransmitters act on postsynaptic cells.

Paracrine signaling

Diffusion of cell products in the ECF to affect neighboring cells.

Autocrine signaling

Cells respond to signals they themselves release.

Endocrine signaling

Hormones reach cells via circulating blood.

Hormones

Chemical messengers in endocrine signaling.

Growth factors

Molecules that reach cells via blood in endocrine signaling.

Interstitial fluid

Fluid between cells; part of the internal environment.

Plasma

The liquid component of blood; part of the extracellular fluid; about 5% of body weight.

Extracellular fluid (ECF)

Fluid outside cells; about 20% of body weight.

Intracellular fluid (ICF)

Fluid inside cells; about 40% of body weight.

Total Body Water (TBW)

60% of body weight as total water content.

Body compartments

Division of the body into intracellular and extracellular compartments.

Negative feedback

Regulatory mechanism that drives the factor in the opposite direction of the change to restore balance.

Positive feedback

Regulatory mechanism that drives the factor in the same direction as the change; occurs rarely.

Homeostasis

The body's effort to maintain a constant internal environment.

Internal environment

The fluid environment in which cells live (interstitial fluid).

37°C

Normal body temperature used as a target in homeostasis.

Temperature regulation

Processes that maintain body temperature (vasoconstriction, vasodilation, sweating, shivering).

Blood vessel constriction

Vasoconstriction to conserve heat.

Blood vessel dilation

Vasodilation to increase heat loss.

Sweat glands

Glands that secrete fluid for evaporative cooling.

Shivering

Involuntary muscle contractions that generate heat.

Heat retention

Heat kept in the body via responses like vasoconstriction.

Heat loss

Heat dissipated by vasodilation and sweating.

Normal body temperature

Target temperature around 37°C in homeostasis.

Chemical messengers

Substances used for intercellular communication (e.g., hormones, neurotransmitters).

Neural communication

Communication via nerve cells and neurotransmitters across synapses.

Paracrine communication

Cell products diffusing in the ECF to affect neighboring cells.

Endocrine communication

Hormones traveling through circulating blood to distant targets.

TBW distribution (general)

TBW is distributed as ICF 40% of body weight and ECF 20% of body weight.

ICF percentage

2/3 of TBW or 40% of total body weight.

ECF percentage

1/3 of TBW or 20% of total body weight.

ISF percentage

15% of total body weight (part of ECF).

Plasma percentage

5% of total body weight (part of ECF).

Intracellular fluid location

Fluid located inside cells.

Extracellular fluid location

Fluid located outside cells.

ISF location

Fluid in the interstitial spaces between cells.

Membrane permeability

Property of the membrane that determines what passes through.

Osmotic movement

Water movement driven by solute concentration differences.

Primary active transport (example)

Active transport requiring energy, e.g., Na+/K+ pump.

Carrier proteins

Proteins that assist transport of substances across membranes.

Energy for transport

ATP provides the energy for active transport.

3 Na+ outward

In the Na+/K+ pump, three Na+ ions are pumped out per cycle.

2 K+ inward

In the Na+/K+ pump, two K+ ions are pumped in per cycle.

Blood group antigens

Antigens on the surface of red blood cells used for blood typing.

Enzyme in membrane

Membrane proteins that catalyze reactions at the membrane.

Receptor-ligand binding

Interaction of receptors with signaling molecules.

Ion movement

Movement of ions across membranes mainly through ion channels.

Passive transport

Diffusion and osmosis that do not require energy.

Active transport requirement

Requires energy (ATP) and carrier proteins.

Gap junction channel

Channel that enables direct cell-to-cell communication.

Synapse

Junction between neurons where signal transmission occurs.

Neurotransmitter release

Release of neurotransmitters at a synaptic junction.

Synaptic cleft

The narrow gap between neurons at a synapse.

Autocrine signaling (note)

Cell responds to signals it releases itself.

Paracrine signaling (note)

Signals diffuse to nearby cells in the extracellular fluid.

Endocrine signaling (note)

Signals travel through circulating blood to distant targets.

TBW distribution calculation (80 kg)

TBW is 60% of body weight; for an 80 kg person TBW ≈ 48 kg.

TBW example (70 kg)

60% of 70 kg equals 42 kg (42 L) TBW.

ISF vs Plasma (ECF components)

ECF comprises ISF (15% body weight) and plasma (5% body weight).

Membrane composition percentages

Proteins ~55%, phospholipids ~25%, cholesterol ~13%, other lipids ~4%, carbohydrates ~3%.

Internal environment stability

Maintenance of constant conditions inside the body’s fluids.

Intercellular communications summary

Communication between cells via gap junctions, neurotransmitters, paracrine, autocrine, and endocrine signals.

Blood plasma function

Transport vehicle for cells, nutrients, hormones, and waste in blood.

Osmosis directionality

Water moves toward higher solute concentration.

Protein functions in membrane

Adhesion, enzymes, antigens, receptors, ion channels, carriers, pumps.

Carriers vs channels

Carriers transport via conformational changes; channels provide pores for ions.

Energy source for diffusion

No energy required for diffusion (passive processes).