Ruirui Bio AP flashcards

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Paracrine signaling

Local signaling where a cell releases signaling molecules that travel a short distance and affect target cells in close proximity. Examples include growth factors and cytokines.

Endocrine Signaling

Long-distance signaling where specialized endocrine cells secrete hormones into the bloodstream. These hormones travel throughout the body to target cells that possess specific receptors. Examples include insulin and estrogen.

Synaptic Signaling

A specialized type of local signaling that occurs between neurons (nerve cells). An electrical signal travels along a neuron and triggers the release of neurotransmitter molecules at a synapse. These neurotransmitters diffuse across the narrow synaptic cleft and bind to receptors on the target neuron, stimulating or inhibiting it. This allows for rapid, targeted communication.

Cell Wall

A rigid, extracellular layer found in plant cells, fungi, algae, and some prokaryotes. Composed primarily of cellulose in plants, chitin in fungi, and peptidoglycan in bacteria. Provides structural support, protection, and helps maintain cell shape. It is permeable.

Plasma Membrane

A selectively permeable barrier surrounding every cell, composed primarily of a phospholipid bilayer with embedded proteins. Controls the movement of substances into and out of the cell, facilitating transport, cell signaling, and maintaining cellular homeostasis. Follows the fluid mosaic model.

Smooth Endoplasmic Reticulum (Smooth ER)

A network of interconnected membrane tubules and sacs lacking ribosomes. Functions include synthesis of lipids (including phospholipids and steroids), detoxification of drugs and poisons, metabolism of carbohydrates, and storage of calcium ions (especially in muscle cells).

Rough Endoplasmic Reticulum (Rough ER)

A network of interconnected membrane tubules and flattened sacs (cisternae) studded with ribosomes on its outer surface. Primary site of synthesis for proteins destined for secretion, insertion into membranes, or residence within certain organelles (e.g., lysosomes). Involved in protein folding and glycosylation.

Golgi Apparatus

An organelle composed of flattened membrane-bound sacs called cisternae, arranged in stacks. Modifies, sorts, and packages proteins and lipids synthesized in the ER for secretion or delivery to other organelles. Has a cis face (receiving) and a trans face (shipping).

Mitochondrion

A double-membraned organelle responsible for cellular respiration, the process of converting glucose and oxygen into ATP (adenosine triphosphate), the cell's primary energy currency. Contains its own DNA and ribosomes, suggesting an endosymbiotic origin. The inner membrane is folded into cristae, increasing surface area for ATP production.

Lysosome

A membrane-bound organelle containing hydrolytic enzymes (acid hydrolases) that function best in an acidic environment. Involved in intracellular digestion, breaking down ingested substances, cellular waste products, and damaged organelles (autophagy). Plays a role in programmed cell death (apoptosis).

Nucleus

A large, double-membraned organelle that contains the cell's genetic material in the form of DNA organized into chromosomes. Controls the cell's activities by regulating gene expression. Contains the nucleolus, where ribosomes are assembled. The nuclear envelope has pores that regulate transport in and out.

Peroxisome

A small, membrane-bound organelle containing enzymes that catalyze various metabolic reactions, including the breakdown of fatty acids (beta-oxidation) and the detoxification of harmful compounds like hydrogen peroxide (H₂O₂), which is converted to water and oxygen by the enzyme catalase.

Chloroplast

A double-membraned organelle found in plant cells and algae that is the site of photosynthesis. Contains chlorophyll, a pigment that captures light energy. Light energy is used to convert carbon dioxide and water into glucose and oxygen. Also contains its own DNA and ribosomes, supporting endosymbiotic theory.

Cytoskeleton

A network of protein fibers extending throughout the cytoplasm, providing structural support, maintaining cell shape, anchoring organelles, and facilitating cell motility and intracellular transport. Composed of three main types of fibers: microtubules, microfilaments (actin filaments), and intermediate filaments.

Vacuole

A large, membrane-bound sac within the cytoplasm of plant cells (central vacuole) and smaller ones in animal and other eukaryotic cells. In plants, the central vacuole stores water, ions, nutrients, pigments, and waste products; it also helps maintain turgor pressure. In animals, vacuoles may be involved in storage or transport.

Centriole

A cylindrical structure composed of microtubules arranged in a 9+0 pattern (nine triplets of microtubules). Found in the centrosome of animal cells and some protists. Involved in the organization of microtubules during cell division (forming the mitotic spindle) and in the formation of cilia and flagella. Plant cells lack centrioles; their spindle fibers form through other mechanisms.