Gas Exchange and Fluid Regulation Chapter 42

Sodium is actively pumped out of the filtrate into the blood, creating a concentration gradient.

Water passively moves out of the filtrate, making it more concentrated

Salts move out of the filtrate, either passively or actively, following a concentration gradient.

Gas exchange across a surface depends upon diffusion driven by differences in partial pressure and other factors.

Blood and water flow in opposite directions to maximize gas or salt exchange.

Drugs can prevent hormones from binding to their receptors, disrupting signaling pathways.

The cell's response to a signal depends on whether the receptor is on the cell membrane or inside the cytosol.

Hormones like estrogen, testosterone, and cortisol can directly pass through the cell membrane.

A complex formed when a lipid-soluble hormone binds to its receptor inside the cell. This complex triggers changes in gene expression.

These hormones cannot directly enter the cell and require signal transduction pathways to relay their message.

The process of converting an extracellular signal into an intracellular signal, often amplified along the way.

A type of receptor that opens an ion channel when a signaling molecule (ligand) binds to it.

A series of protein activations by adding phosphate groups, often used in signal transduction pathways.

The stage in the cell cycle where the cell grows and synthesizes proteins, mitochondria, and other organelles. This prepares the cell for mitosis.

A checkpoint in the cell cycle that checks for sufficient nutrients, favorable environmental conditions, and proper growth factors. This ensures the cell is ready to replicate its DNA.

Structures within the cytoplasm that form during G2 and are responsible for organizing microtubule formation, which are essential for cell division (mitosis).

Thin fibers responsible for cell movement, contraction, and the separation of animal cells during cytokinesis. They form two coiled strands.

Strong, rope-like fibers that provide structural support to cells. They are thicker than actin filaments.

Hollow tubes made of alpha and beta subunits that are involved in cell shape, organelle transport, and the formation of the mitotic spindle.

The first stage of mitosis where the nuclear envelope starts dissolving, chromosomes condense, and sister chromatids become visible.

The stage of mitosis where the nuclear membrane completely dissolves, kinetochores attach to microtubules, and the mitotic spindles move to the cell poles.

The electrical charge difference across a neuron's membrane when it's not actively transmitting a signal. It's usually negative due to more negative ions inside the cell compared to outside.

A protein embedded in the neuron's membrane that actively pumps sodium ions out and potassium ions into the cell, creating a concentration gradient.

The initial phase of an action potential where the membrane potential becomes less negative, moving towards a more positive charge. It's triggered by sodium ions rushing into the cell.

The minimum level of depolarization required to trigger an action potential. If the membrane potential doesn't reach this threshold, no signal is sent.

A rapid temporary change in the membrane potential of a neuron, caused by the flow of ions across the membrane. It's the way neurons communicate.

A complex of cyclin and cyclin-dependent kinase (CDK) that drives the cell from G2 phase into M phase (mitosis). It activates a cascade of proteins that ultimately leads to cell division.

An enzyme that, when bound to cyclin, phosphorylates other proteins to trigger different stages of the cell cycle. CDK activity is regulated by the presence and concentration of cyclin.

A protein that activates CDK and whose concentration fluctuates throughout the cell cycle. Different cyclins are responsible for each phase of the cell cycle.

A tumor suppressor protein that when unphosphorylated, binds to E2F (a transcription factor) and blocks the cell cycle from entering S phase (DNA replication).

A transcription factor that activates the expression of genes involved in DNA replication and cell division.

A checkpoint in the cell cycle that ensures that all chromosomes are properly attached to microtubules of the spindle apparatus before the cell divides.

The process of moving sugars from source cells (like leaves) to companion cells in the phloem.

A protein in the companion cell membrane that actively transports both hydrogen ions and sucrose into the cell, using energy from the proton gradient.

The pressure exerted by the fluid inside the phloem cells, pushing the sap towards sink cells.

The process of moving sugars from the companion cells to the sink cells, where they are used or stored.

The membrane that surrounds the large vacuole in root cells, playing a role in controlling the movement of sucrose.

A protein in the tonoplast that uses the electrochemical gradient to bring sucrose into the vacuole while exporting hydrogen ions.

Fungi that form a symbiotic (mutually beneficial) relationship with plant roots, helping them absorb nutrients.

The process of roots absorbing essential nutrients from the soil, using active and passive transport mechanisms.

A second set of jaws found in some fish, located in the throat, used for crushing and grinding food.

Cichlids have a pharyngeal jaw that bites more effectively due to the arrangement and specialization of its teeth.

Salivary amylase is an enzyme in saliva that begins the breakdown of carbohydrates in the mouth.

Lingual lipase is an enzyme found in the mouth that starts breaking down lipids (fats).

Pepsin is an enzyme in the stomach responsible for breaking down proteins into smaller peptides.

An animal that maintains the same internal osmolarity as its surrounding environment, requiring less energy to regulate.

An animal that actively regulates its internal osmolarity, maintaining a constant concentration even when the external environment changes.

Urea is a moderately soluble, moderately toxic form of nitrogenous waste produced by mammals.