Cell Biology

Concepts, terms, etc.

Cell theory

A scientific explanation of what cells are and the relationship between cells and living things.

What does the Cell Theory state?

I. All living things are made up of one or more cells
II. Cells are the smallest living unit in all organisms
III. All cells come from other pre-existing cells (through whatever means)

Unicellular

Something that is made up of one cell, a single-celled organism. Has one cell.
Example: Amobea

Multicellular

Something that is made up of more than one cell, consists of many cells. Has multiple cells.
Example: Humans

What do prokaryotes and eukaryotes have in common

Genetic material (DNA), cytoplasm, ribosomes, cell plasma membrane

What are prokaryotes?

Bacteria and Archaea

What are eukaryotes?

Animals, plants, fungi, protists

What defines prokaryotes?

No nucleus (pro rhymes with no) and no membrane-bound organelles (e.g. no mitochondria or Golgi apparatus),

What defines eukaryotes?

They do have nucleus (eu rhymes with do) and membrane-bound organelles (such as mitochondria and Golgi apparatus),

Cell membrane

Also called plasma membrane, it's a thin, flexible barrier around the cell that regulates which substances enters and exits. It's selectively permeable, meaning it selects what goes in and out. This keeps homeostasis in the cell (keeps it stable). Found in both prokaryotes and eukaryotes.

Cytoplasm

A jellylike substance inside the cell and all around the outside of the nucleus. It holds/surrounds all the organelles of the cell. Found in both prokaryotes and eukaryotes.

Cytoskeleton

A network of protein/fibers that hold the cell together and provides supports to the organelles inside. It helps the cell keep its shape and majorly aids in movement. Found in both prokaryotes and eukaryotes.

Ribosomes

Non-membrane bounded organelles responsible for protein synthesis, meaning they make proteins. They can either be floating free around in the cell or attached to other organelles. Found in both prokaryotes and eukaryotes.

Nucleus

Only in eukaryotes, it holds the genetic material (DNA and RNA). Controls the cell and its activities.

Nucleolus

Found inside the nucleus and produces ribosomes.

Endoplasmic Reticulum (ER)

Attached to the nuclear membrane as a folded maze of passageways. It does a lot of the processing of molecules (e.g. protein folding) for the cell and highly aids in transport.

Rough Endoplasmic Reticulum (RER)

The region of the ER that has ribosomes attached to it like small, rounded spikes. Aids/involved in protein processing and transport. Sends of molecules from the ER in vesicles.

Smooth Endoplasmic Reticulum (SER)

The region of the ER that has little to no ribosomes attached to it, making it smooth. It takes care of additional roles. Detoxification and creation of certain lipids are among its "jobs".

Golgi apparatus

A system of membranes and vesicles in eukaryotic cells that modifies, sorts and packages proteins to be secreted (exported) from the cell. It has enzymes that modifies the molecules it receives (often from the ER).

Mitochondria

The powerhouse of the cell. It makes ATP through a process called cellular respiration. It runs on glucose and partly oxygen. They have a double membrane, the inner one is folded and runs on its own genome. They divide independently through fission.

What are eukaryotes divided in? (It's not a one size fits all)

Animal cells and plant cells

What defines plant cells?

They have chloroplast in addition to mitochondria. Large vacuoles called center vacuoles. They have a cell wall in addition to the cell membrane.

What defines animal cells?

No chloroplast or cell wall (only membrane). They have many smaller vacuoles instead of one big.

Cholorplast

A green organelle in plant cells that makes glucose by using light energy in photosynthesis.

Vacolues

Exist in eukaryotes, both animal and plant cells. It has multiple functions, especially acting as storage for materials

Cell wall

A rigid layer that surrounds the cell membrane and provides additional support, protection and shape maintenance to the cell.

How proteins leave the cell? (Generally)

Firstly they are made by a ribosome with instructions from the DNA in the nucleus. The ribosome attached to the ER would send it off "the ER highway" where the proteins would be put in a vesicle. The vesicle with the ribosomes would travel to the Golgi apparatus where they could be tagged for secretion, put in yet another vesicle and sent to the membrane that they leave out of.

Lysosomes

Cell organelle filled with enzymes needed to break down certain materials in the cell. Mainly found in eukaryotic cells.