Study Notes: Cell Membrane, Transport, Organelles, Metabolism, Mitosis, and Genetics

Cell Membrane (Plasma Membrane)

A phospholipid bilayer that forms the barrier between the inside and outside of the cell, regulating what enters and leaves to maintain homeostasis.

Phospholipid Bilayer

Two layers of phospholipids that form the structural basis of the cell membrane.

Membrane Channels and Carriers

Proteins embedded in or through the cell membrane that move substances in and out of the cell.

Homeostasis

The process by which the cell membrane regulates what enters and leaves, maintaining balanced water, pH, and electrical charge.

Receptors (on cell membrane)

Proteins on the cell membrane that detect changes in the outside environment (e.g., Na⁺ concentration, temperature) and trigger responses.

Cytoskeleton

Internal scaffolding to which the cell membrane attaches, helping maintain cell shape and stability.

Selective Permeability

The property of the cell membrane that allows some substances to pass while blocking others to maintain internal balance.

Anchoring Proteins

Membrane proteins that anchor the cytoskeleton to the membrane to maintain cell shape.

Recognition Proteins

Membrane proteins that help the cell recognize self (identifying what belongs) vs. foreign substances.

Membrane Enzymes

Membrane proteins that catalyze reactions at the membrane (often ending in -ase).

Receptor Proteins (Membrane)

Membrane proteins that receive information from the outside environment to trigger a cellular response.

Transport Proteins

Membrane proteins that help move substances (solutes, ions, large molecules) across the membrane.

Cell Adhesion Proteins

Membrane proteins that help cells stick together or form barriers (cell-to-cell binding).

Concentration Gradient

The difference in concentration of a substance inside vs. outside the cell, causing substances to tend to move from high to low concentration.

Simple Diffusion

Passive transport where small particles move directly through the membrane without energy (e.g., water, O₂, CO₂).

Facilitated Diffusion

Passive transport that requires help from channels or carriers but no energy, for ions or larger molecules.

Channel-mediated Diffusion

A type of facilitated diffusion involving movement of substances through membrane channels.

Carrier-mediated Diffusion

A type of facilitated diffusion where a carrier molecule transports a solute across the membrane.

Osmosis

The diffusion of water across a semipermeable membrane toward a higher solute concentration (lower water concentration) to equalize concentrations.

Isotonic Solution

An extracellular solution with an equal solute concentration compared to the cell's interior, resulting in no net water movement and a stable cell size.

Hypertonic Solution

An extracellular solution with a higher solute concentration than the cell's interior, causing water to leave the cell and the cell to shrink (crenation).

Hypotonic Solution

An extracellular solution with a lower solute concentration than the cell's interior, causing water to enter the cell and the cell to swell, potentially leading to bursting (lysis).

Active Transport

Movement of substances from low to high concentration (against the gradient) requiring energy, primarily from ATP.

ATP (Adenosine Triphosphate)

The primary energy source for active transport and other cellular processes; energy is released when a phosphate group is removed.

Na⁺/K⁺ Pump

A canonical example of active transport that pumps three Na⁺ ions out of the cell and two K⁺ ions into the cell per ATP molecule, maintaining electrical charge and homeostasis.

Vesicular Transport

A mechanism to move large particles or bulk materials into (endocytosis) or out of (exocytosis) the cell using vesicles.

Endocytosis

The process of importing material into the cell where the plasma membrane forms a vesicle to engulf the substance.

Exocytosis

The process of exporting material from the cell where a vesicle fuses with the membrane to release its contents outside.

Nucleus

The control center of the cell that houses DNA and provides instructions for cell identity and function.

Mitochondria

The "powerhouse" of the cell responsible for generating ATP (energy) through aerobic respiration when oxygen is available.

Endoplasmic Reticulum (ER)

A network of membranes involved in synthesis; Rough ER (with ribosomes) synthesizes proteins, and Smooth ER synthesizes lipids.

Golgi Apparatus

The "post office" of the cell; packages, processes, and sorts proteins and lipids for transport or internal use.

Lysosomes

Organelles that act as the "cleaning crew" of the cell, degrading waste products and harmful materials.

Ribosomes

Protein synthesis machines that translate genetic information into proteins.

Glycolysis

The initial breakdown of glucose in the cytosol, producing a net gain of 2 \, \mathrm{ATP} per glucose.

Aerobic Respiration

Energy production pathway occurring in mitochondria when oxygen is available, involving the Krebs cycle and oxidative phosphorylation, yielding approximately 36 \, \mathrm{ATP} per glucose.

Anaerobic Respiration

Energy production pathway occurring when oxygen is limited, yielding much lower ATP and potentially leading to lactic acid accumulation.

Transcription

The process in the nucleus where DNA is used to synthesize messenger RNA (mRNA).

Translation

The process in the cytoplasm (at ribosomes) where mRNA is translated into a protein, with the help of tRNA and rRNA.

mRNA (messenger RNA)

Carries the genetic message from DNA in the nucleus to the ribosome for protein synthesis.

tRNA (transfer RNA)

Acts as a translator, bringing specific amino acids to the ribosome and matching them to mRNA codons during translation.

rRNA (ribosomal RNA)

A component of the ribosome that helps link amino acids together to form proteins.

Mitosis

The cellular process of duplicating the cell’s DNA and dividing into two genetically identical daughter cells.

Interphase

The stage before mitosis when the cell is functioning and not actively dividing, representing most of a cell's life.

Prophase (Mitosis)

Stage of mitosis where chromosomes condense and become visible, and the spindle apparatus begins to form.

Metaphase (Mitosis)

Stage of mitosis where chromosomes line up along the middle equator of the cell.

Anaphase (Mitosis)

Stage of mitosis where sister chromatids are pulled apart toward opposite poles, and the cell elongates.

Telophase (Mitosis)

Stage of mitosis where chromosomes arrive at poles, the nuclear envelope reforms, and two nuclei are formed.