Cell Structure and Function Flashcards

These flashcards cover cell structure and function, including membrane transport, cell communication, and organelle roles as described in the lecture notes.

Plasma Membrane

A semipermeable structure that separates intra- and extracellular environments and controls transport, signaling, and electrical currents.

Lipid bilayer

The component of the plasma membrane consisting of a hydrophilic head and a hydrophobic tail; it is insoluble to water and soluble to lipids.

Channels

Proteins in the cell membrane that selectively allow certain materials through the membrane.

Receptors

Proteins that bind a ligand to cause an effect in the cell.

Ligand

A messenger molecule that attaches to receptor proteins.

Upregulation

A process of increasing the number of receptors to regulate cell responses to chemical messengers.

Downregulation

A process of decreasing the number of receptors to regulate cell responses to chemical messengers.

First messengers

Molecules that bind receptors, including steroids, neurotransmitters, growth factors, and protein hormones.

G protein–linked receptors

A type of cell surface receptor that often utilizes cyclic AMP (cAMP) as a second messenger.

Ion channel–linked receptors

Receptors specialized for rapid signaling, such as nerve impulses and muscle cell actions.

Intracellular receptors

Receptors located in the cytoplasm that bind lipid-soluble thyroid and steroid hormones to initiate transcription.

Diffusion

A passive process where substances move from areas of higher concentration to areas of lower concentration without requiring ATP.

Facilitated Diffusion

A passive process occurring via channel or carrier proteins for substances that cannot cross the lipid bilayer due to size, charge, or polarity.

Osmosis

The diffusion of water across a semipermeable membrane occurring when there is an imbalance of solutes inside versus outside the cell.

Active transport

A process requiring energy to move solutes across the membrane against the concentration gradient.

$Na^+/K^+$ pump

An active transport mechanism that moves $3\,Na^+$ out of the cell and $2\,K^+$ into the cell against their concentration gradients.

Endocytosis

Vesicular transport where cells surround and take in material from their surroundings.

Pinocytosis

A form of endocytosis known as 'cell drinking,' involving the intake of fluids and electrolytes.

Phagocytosis

A form of endocytosis known as 'cell eating,' involving the intake of microbes.

Exocytosis

The secretion of intracellular substances into the extracellular space.

Nucleus

The cell component containing the genome and enzymes required for replication and transcription.

Ribosomes

Nucleoproteins composed of rRNA and proteins focused on protein synthesis.

Endoplasmic Reticulum

An organelle that makes proteins (rough) and lipids or steroids (smooth).

Golgi apparatus

The organelle responsible for packaging proteins within the cell.

Lysosomes

Organelles responsible for the digestion of unwanted materials.

Peroxisomes

Organelles that perform oxidative reactions, such as converting $H_2O_2 \rightarrow H_2O$, and produces bile acids in the liver.

Proteasomes

Structures that break down deranged proteins marked for destruction through ubiquitination.

Mitochondria

Known as the powerhouse of the cell, this organelle is the site where work happens and regulates apoptosis.