Biology Chapter 4

The thin layer of lipids and proteins that sets a cell off from its surroundings and acts as a selective barrier to the passage of ions and molecules into and out of the cell; consists of phospholipid bi layer in which are embedded molecules of protein and cholesterol.

A cell organelle consisting of RNA and protein organized into two subunits and functioning as the site of protein synthesis in the cytoplasm. the ribosomal subunits are constructed in the nucleolus.

The combination of DNA and proteins that constitutes chromosomes; often used to refer to the diffuse, very extended form taken by the chromosomes when a eukaryotic cell is not dividing.

A network of interconnected membranous sacs in a eukaryotic cell's cytoplasm. Rough ER membranes are studded with ribosomes that make membrane proteins and secretory proteins. Rough ER constructs membrane from phospholipids and proteins.

A network of interconnected membranous tubules in a eukaryotic cell's cytoplasm. Smooth ER lacks ribosomes. Enzymes embedded in the smooth ER membrane function in the synthesis of certain kinds of molecules, such as lipids.

An extensive membranous network in a eukaryotic cell, continuous with the outer nuclear membrane and composed of ribosome-studded (rough) and ribosome-free (smooth) regions.

Membrane-bound vesicle in the cell cytoplasm containing powerful enzymes that detoxify harmful or toxic substances.

A meshwork of fine fibers in the cytoplasm of a eukaryotic cell, includes microfilaments, intermediate filaments, and microtubules.

A contractile protein of muscle. Forms the thin filaments in the myofibrils.

One of the principal contractile proteins found in muscle. Myosin is composed of thick filaments with cross-bridges.

A short appendage that propels some protists through the water and moves fluids across the surface of many tissue cells in animals. In common with eukaryotic flagella, cilia have a 9 + 2 arrangement of microtubules covered by the cell's plasma membrane.

A eukaryotic cell organelle consisting of a 9 + 0 arrangement of microtubule triplets; may organize the micro-tubule assembly of a cilium or flagellum; structurally identical to a centriole.

A membrane-enclosed sac, part of the endomembrane system of a eukaryotic cell, having diverse functions.

The genetic control center of a eukaryotic cell.

A double membrane, perforated with pores, that encloses the nucleus and separates it from the rest of the eukaryotic cell.

A threadlike, gene-carrying structure found in the nucleus of a eukaryotic cell and most visible during mitosis and meiosis; also, the main gene-carrying structure of the prokaryotic cell. Chromosomes consist of chromatin.

A small membrane-bound , fluid-filled sac that encloses and contains certain substances within a cell.

An organelle in eukaryotic cells where cellular respiration occurs. Enclosed by two concentric membranes, it is where most of the cell's ATP is made.

The thickest of the three main kinds of fibers making up the cytoskeleton of a eukaryotic cell; a straight, hollow tube made of globular proteins called tubulins. Microtubules form the basis of the structure and movement of cilia and flagella.

A temporary extension of an amoeboid cell. Pseudopodia function in moving cells and engulfing food.

Adensosine triphosphate, the main energy source for cells.

A protective layer external to the plasma membrane in plant cells, bacteria, fungi, and some protists; protects the cell and helps maintain its shape.

A junction that binds tissue cells together in a leak proof sheet.

Everything inside a cell between the plasma membrane and the nucleus; consists of a semifluid medium and organelles.

A structure within the nucleus of a eukaryotic cell where ribosomal RNA is made and assembled with proteins to make ribosomal subunits; consists of parts of the chromatin DNA, RNA transcribed from the DNA, and proteins imported from the cytoplasm.

An organelle in eukaryotic cells consisting of stacks of membranous sacs that modify, store, and ship products of the endoplasmic reticulum.

A digestive organelle in eukaryotic cells; contains hydrolytic enzymes that digest the cell's food and wastes.

An organelle found in plants and photosynthetic protists. Enclosed by two concentric membranes, a chloroplast absorbs sunlight and uses it to power the synthesis of organic food molecules (sugars).

The thinnest of the three main kinds of protein fibers making up the cytoskeleton of a eukaryotic cell; a solid, helical rod composed of globular protein actin.

A long appendage that propels protists through the water and moves fluids across the surface of many tissue cells in animals. A cell may have one or more flagella. Like cilia, flagella have a 9 + 2 arrangement of microtubules covered by the cell's plasma membrane.

A channel between adjacent tissue cells through which water and other small molecules pass freely.

A structure in an animal cell composed of microtubule triplets arranged in a 9 + 0 pattern. An animal cell usually has a pair of centrioles within each of it centrosomes.

An open channel in a plant cell wall, through which strands of cytoplasm connect from adjacent walls.