Cell Physiology Lecture Notes

Comprehensive vocabulary flashcards covering cell anatomy, organelle functions, membrane transport mechanisms, and cell life cycle regulation based on the Week Two Cell Physiology lecture.

Insulin

A hormone released from the pancreas in response to increased blood glucose levels that utilizes negative feedback to stop blood glucose from continuing to rise or staying elevated.

Hypothalamus

The thermoregulatory center in the brain responsible for receiving signals from receptors and sending commands to effectors to maintain body temperature.

Plasma Membrane

The outer boundary of the cell that provides physical isolation, regulates exchange with the environment, senses environmental changes, and offers structural support.

Phospholipid bilayer

The structural foundation of the plasma membrane consisting of hydrophilic heads facing outward and hydrophobic fatty-acid tails inside the membrane.

Integral proteins

Membrane proteins that are positioned within the phospholipid bilayer.

Peripheral proteins

Proteins bound to the inner or outer surface of the plasma membrane.

Receptor proteins

Membrane proteins that bind and respond to specific ligands, such as ions or hormones.

Glycocalyx

A sticky "sugar coat" formed by proteoglycans, glycoproteins, and glycolipids that functions in lubrication, protection, anchoring, and cell recognition.

Cytosol

The intracellular fluid containing dissolved nutrients, ions, proteins, and waste products; it has high levels of protein and potassium ($K^+$).

Organelles

Structures within the cell and cytoplasm that perform specific functions, such as the nucleus or mitochondria.

Cytoskeleton

A network of structural proteins including microfilaments, intermediate filaments, and microtubules that provide shape and strength to the cell.

Microfilaments

Thin filaments composed of the protein actin that provide mechanical strength and interact with myosin for muscle contraction.

Intermediate filaments

Durable mid-sized filaments that strengthen the cell, maintain its shape, and stabilize the position of organelles and the cell itself.

Microtubules

Large, hollow tubes of tubulin proteins that anchor organelles, change cell shape, and form the spindle apparatus used during cell division.

Microvilli

Extensions of the plasma membrane that increase surface area for absorption and are attached to the cytoskeleton.

Centrioles

Non-membranous organelles composed of nine microtubule triplets in a $9+0$ array that form the spindle apparatus during cell division.

Motile cilium

A slender extension of the plasma membrane containing a $9+2$ array of microtubules that moves fluids across the cell surface.

Ribosomes

Organelles responsible for protein synthesis; they contain ribosomal RNA ($rRNA$) and can be free in the cytoplasm or fixed to the Endoplasmic Reticulum.

Proteasomes

Organelles containing proteases that disassemble and recycle damaged proteins.

Mitochondria

Membranous organelles with a double membrane and inner folds called cristae that produce $95\%$ of the ATP required by the cell.

Rough Endoplasmic Reticulum (RER)

A network of membranous channels covered with ribosomes that is active in protein and glycoprotein synthesis.

Smooth Endoplasmic Reticulum (SER)

A network of membranous channels without ribosomes that synthesizes phospholipids, cholesterol, steroid hormones, glycerides, and glycogen.

Golgi apparatus

A series of flattened membranes (cisternae) that modifies and packages secretions, such as hormones and enzymes, for release from the cell.

Lysosomes

Vesicles produced by the Golgi apparatus containing powerful enzymes that destroy bacteria and recycle damaged organelles.

Peroxisomes

Small, enzyme-containing vesicles that break down organic compounds such as fatty acids.

Catabolism

The metabolic process of breaking down complex molecules into simple ones for degradation.

Anabolism

The metabolic process of synthesizing molecules to build or support organs and tissues (biosynthesis).

Selectively permeable

A property of the plasma membrane that restricts movement based on size, electrical charge, molecular shape, and lipid solubility.

Diffusion

The passive net movement of a substance from an area of higher concentration to an area of lower concentration.

Osmosis

The diffusion of water across a selectively permeable membrane toward a solution with a higher concentration of solutes.

Osmotic pressure

The force with which pure water moves into a solution due to solute concentration; it is equal to the hydrostatic pressure required to stop osmotic flow.

Osmolarity

The total solute concentration in a specific volume of solution.

Isotonic solution

A solution with the same solute concentration as the cell, causing no osmotic flow or change in cell size.

Hypotonic solution

A solution with a lower solute concentration than the cell, causing water to enter and the cell to swell or undergo lysis (hemolysis).

Hypertonic solution

A solution with a higher solute concentration than the cell, causing water to leave the cell and the cell to shrink (crenation).

Facilitated diffusion

A passive transport process where carrier proteins move molecules like glucose and amino acids across the membrane using specific receptor sites.

Sodium–potassium exchange pump

A primary active transport mechanism where one ATP powers the movement of three sodium ions ($Na^+$) out and two potassium ions ($K^+$) in.

Secondary active transport

A process where ATP is used to establish a concentration gradient of one substance (like $Na^+$) to passively transport another (like glucose).

Phagocytosis

A vesicular transport process where large objects are engulfed in phagosomes using cytoplasmic extensions called pseudopodia.

Pinocytosis

A process of endocytosis where endosomes "drink" or bring extracellular fluid into the cell.

Exocytosis

A process where a cell vesicle fuses with the plasma membrane to release materials like hormones or proteins to the extracellular fluid.

Cellular differentiation

The process by which cells turn off genes not needed by that specific cell type, allowing the formation of specialized cells like liver cells or neurons.

p53

A protein that arrests the cell cycle when DNA damage is detected; a mutated version fails to stop the cycle and may result in cancer.