Cells 1

01/29/2025

Why are cells small?

Most chemical reactions require diffusion, this cannot occur over a long distance. Distance travelled is proportional to time.

What are the two organizational patterns of cells?

Prokaryotes and Eukaryotes.

Defining characteristic of prokaryotes

• No nucleus (nucleoid region)

Defining characteristic of eukaryotes

• Compartmentalization

• Different structures have specialized functions

• Membrane bound organelles

What happens in the nucleus?

• DNA is replicated

• DNA is transcribed into mRNA and rRNA by RNA polymerase

• RNA folds directly into 3D structure

What are ribosomes made of?

4 rRNAs and 80 proteins in the nucleolus.

How many cells are in the human body?

40 trillion

What do plant cells have that animal cells do not?

Cell wall

Why is compartmentalization important? How does it work?

It allows cells to grow larger. Many internal membrane systems create specialized spaces that allow diffusion to happen quickly.

What mediates compartmentalization?

The endomembrane system (nucleus, ER, golgi, vesicles and lysosomes).

What surrounds the nucleus?

The nuclear envelope, which is made up of two membranes.

How do ribosomes pass from the nucleolus to the cytoplasm?

Through the nuclear pores.

What borders the nucleus?

The rough ER.

Where are all membrane lipids made?

In the smooth ER.

Where does detoxification occur?

The smooth ER as well.

Different cells can have different amounts of ____ according to cell function/human behaviour.

organelles. For example, drug users have more smooth ER in their liver cells.

What is the golgi apparatus?

• A stack of membranes generated by vessicles coming from the ER and fusing.

What does the golgi apparatus do?

Further modifies proteins and lipids. Sugar side chains are added and proteins are sorted.

“Amazon” of the cell.

What do pulse-chase experiments demonstrate?

The travelling of proteins through the endomembrane system.

Endocytosis

Cell absorbs materials from the environment by the membrane invaginating.

Phagocytosis

Cell engulfs materials.

What is autophagy?

Self-eating. Lysosomal membranes can surround entire organelles and chunks of cytoskeleton.