Cell Theory & Parts

cell membrane

The boundary of a cell made of a phospholipid bilayer with proteins embedded within it. In all cells.

cell wall

A rigid structure that surrounds the cell membrane and provides support to the cell. Not in animal cells and some protists. In bacteria, plant, and fungal cells. Some protists have a cell wall. In plants the cell wall is made of cellulose.

cytosol

Fluid portion of cytoplasm. Contains water and ions (Ca, Na, Cl). Where chemical reactions happen. In all cells.

cytoplasm

the portion of the cell (outside the nucleus if eukaryotic) within the cell membrane. In all cells.

phospholipid

the type of lipid used to make cell and organelle membranes; contains a hydrophilic head and 2 hydrophobic tails

smooth endoplasmic reticulum

An organelle near the nucleus (with no ribosome attached) that contains enzymes for synthesizing lipids and detoxifying drugs. In eukaryotes only.

rough endoplasmic reticulum

An organelle near the nucleus that is studded with ribosomes and makes complex proteins for transport around the cell and secretion outside the cell. In eukaryotes only.

golgi apparatus

An organelle made of a system of membranes that modifies and packages proteins for export from the cell. In eukaryotes only.

central vacuole

A large vacuole organelle that is filled with a solution that contains a high concentration of solutes and water. In eukaryotic plant cells only.

contractile vacuole

The organelle that collects extra water from the cytoplasm and then expels it from the cell to maintain homeostasis. In eukaryotic protists called paramecium.

vesicle

Small membrane-bound sac that functions in moving products into, out of, and within a cell and between organelles within the cell. In eukaryotes only.

lysosome

A small, round organelle containing chemicals that break down large food particles into smaller ones. In eukaryotic animal cells only. (Other eukaryotes have "lytic vacuoles" that are similar.)

cytoskeleton

A network of structural proteins called microtubules & microfilaments that hold the cell together, helps the cell to keep its shape, and aids in movement. In all cells!

chloroplasts

Organelles that capture the energy from sunlight and convert it into chemical energy in a process called photosynthesis. In all plants cells and some protists. In eukaryotes only- all plant cells and some protists (algae).

mitochondria

Powerhouse of the cell, organelle that is the site of energy production (ATP). In eukaryotes only.

chromatin

Filaments of DNA bound to proteins.

nucleus

A part of the cell containing DNA. In eukaryotes only.

nucleolus

Found inside the nucleus and produces ribosomes. In eukaryotes only.

centrioles

Organelle that aids in cell division. In eukaryote animal cells only.

enosymbiotic theory

A theory that states that certain kinds of prokaryotes were eaten (but not digested) and began living inside of larger cells. They evolved into the organelles of modern-day eukaryotes.

cell theory

A theory that all living things are composed of cells, cells are the basic units of structure and function in living things, and new cells are produced from existing cells.