IB Biology Topic A2.2: Cell Structure Key Definitions

70S ribosomes are small ribosomes found in prokaryotic cells, as well as in the mitochondria and chloroplasts of eukaryotic cells. They are responsible for protein synthesis, translating messenger RNA (mRNA) into functional proteins.

80S ribosomes are larger ribosomes found in eukaryotic cells that synthesize proteins.

A fundamental principle of biology stating that:

• All living organisms are composed of one or more cells.
• The cell is the basic unit of structure and function in all living things.
• All cells arise from pre-existing cells.

The cell wall is a rigid, protective layer located outside the plasma membrane of certain cells, including prokaryotes, plants, fungi, and some protists. It provides structural support, protection, and shape to the cell.

An organelle found in plant and algal cells that is responsible for photosynthesis, the process of converting light energy into chemical energy

A coenocyte is a multinucleated cell-like structure formed by repeated nuclear divisions without cell division.

Convergent evolution is when distantly related organisms independently evolve similar traits or behaviors to adapt to similar environments

An advanced form of electron microscopy that studies biomolecules (especially proteins) in their natural, hydrated state.

The cytoplasm is the jelly-like substance inside a cell, excluding the nucleus, where various cellular activities occur.

A network of protein fibers, including microtubules, microfilaments, and intermediate filaments.

Differentiation is the process where pluripotent cells (unspecialized cells) develop into specialized cells with unique structures and functions.

A double-stranded molecule that stores and transmits genetic information in living organisms.

A network of membranes involved in synthesis and transport.

Endosymbiosis refers to one organism living inside another in a mutually beneficial relationship.

A eukaryote is a type of cell that contains a nucleus and membrane-bound organelles, enabling it to carry out specialized and coordinated functions. These cells are found in plants, animals, fungi, and protists.

An eyepiece graticule is a small scale etched onto the eyepiece lens of a microscope.

A specialized technique for studying the internal structure of cell membranes.

Gene expression is the process of using genetic information to produce functional products like proteins.

The genome is the complete set of genetic instructions that determines the structure, function, and traits of an organism.

A stack of flattened, membrane-bound sacs that process, package, and distribute proteins and lipids.

Organisms that obtain energy and carbon by consuming other organisms or organic matter.

Lysosomes are specialized vesicles containing digestive enzymes.

Organelles such as the nucleus, lysosomes, and vacuoles are surrounded by lipid bilayers, which act like security doors—letting the right molecules in and keeping the wrong ones out.

The sum of all chemical reactions occurring in an organism to maintain life, including reactions that break down molecules for energy (catabolism) and reactions that build molecules for growth and repair (anabolism).