Structure and Function of Cells

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Prokaryotic cell Noun

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[pro-kar-ee-ot-ik sel]

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Prokaryotic cell

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A simple cell type lacking a true nucleus, with its genetic material located in a region called the nucleoid.

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Example: This diagram shows the structure of a prokaryotic cell (a bacterium), which is a simple cell that lacks a nucleus and has its DNA floating in a nucleoid area.

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Eukaryotic cell Noun

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[yoo-kar-ee-ot-ik sel]

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Eukaryotic cell

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A complex cell type characterized by a true nucleus enclosing its DNA and the presence of many membrane-bound organelles.

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Example: This diagram shows an animal cell, an example of a eukaryotic cell, which has a true nucleus and other membrane-bound organelles like mitochondria.

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Nucleoid Noun

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[noo-klee-oid]

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Nucleoid

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The non-membrane-bound region within a prokaryotic cell that contains the cell's primary genetic material.

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Example: This diagram shows a simple cell, like a bacterium, and points to the nucleoid, which is the area inside where the cell's main genetic material is located.

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Nucleus Noun

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[noo-klee-us]

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Nucleus

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A large, membrane-bound organelle in eukaryotic cells that houses the genetic material and controls cellular activities.

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Example: This diagram shows a cutaway view of the cell's nucleus, labeling its key parts like the chromatin (genetic material) and the protective nuclear envelope.

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Organelle Noun

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[or-guh-nel]

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Organelle

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A specialized subunit within a cell that performs a specific function and is often enclosed by its own membrane.

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Example: This image shows the detailed structure of a mitochondrion, which is one type of organelle found inside a cell.

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Cell Membrane Noun

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[sel mem-brayn]

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Cell Membrane

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The selectively permeable outer boundary of a cell, composed of a phospholipid bilayer, regulating passage of substances.

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Example: This image shows the cell membrane is a flexible barrier made of a phospholipid bilayer with different types of proteins embedded within it.

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Phospholipid bilayer Noun

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[fos-fo-lip-id by-lay-er]

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Phospholipid bilayer

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The two-layered molecular sheet forming the core of all cell membranes, with hydrophilic heads and hydrophobic tails.

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Example: This diagram shows the phospholipid bilayer, a double layer of molecules that forms cell membranes, with water-loving heads facing out and water-fearing tails facing in.

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Selectively permeable Adjective

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[suh-lek-tiv-lee per-mee-uh-bul]

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Selectively permeable

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A property of biological membranes that allows only certain molecules or ions to pass through it by means of diffusion.

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Example: A selectively permeable membrane acts like a filter, allowing small particles to pass through its pores but blocking larger particles from crossing.

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Ribosomes Noun

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[ry-bo-sohmz]

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Ribosomes

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Small cellular particles made of RNA and protein that are responsible for synthesizing proteins from amino acid chains.

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Example: This diagram shows a ribosome, made of two subunits, reading instructions from an mRNA molecule to build a protein, called a peptide chain.

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Endoplasmic Reticulum (ER) Noun

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[en-do-plaz-mik reh-tik-yoo-lum]

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Endoplasmic Reticulum (ER)

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A network of membranous tubules within a eukaryotic cell's cytoplasm, involved in protein and lipid synthesis and modification.

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Example: This diagram shows the location of the endoplasmic reticulum (both rough and smooth) inside an animal cell, near the nucleus.