Cell Biology: Ribosomes and Endocytosis

Study Notes

Endocytotic vesicles can fuse with lysosomes to break down their contents.
Ribosomes are produced in the nucleolus and are the sites of protein synthesis.
Ribosomes can be free-floating or attached to the endoplasmic reticulum (ER).
Peroxisomes are small vesicles containing enzymes for breaking down harmful substances, such as hydrogen peroxide, which can be toxic to cells.
The endoplasmic reticulum (ER) consists of a series of membranes forming sacs and tubules extending from the nuclear membrane into the cytoplasm.

The nucleus is surrounded by a double membrane called the nuclear envelope, which has an outer and inner membrane with a narrow perinuclear space.
The nuclear membrane contains nuclear pores that control the passage of materials in and out of the nucleus.
Human cell nuclei contain several pairs of chromosomes, composed of DNA and proteins, existing loosely during interphase as chromatin and becoming coiled during cell division.
The nucleus contains one or more nucleoli, which are non-membrane-bound structures involved in ribosome production.

Also known as the Golgi complex, it consists of closely packed, curved, membrane-bound sacs.
The Golgi apparatus functions in processing and packaging proteins and lipids, forming vesicles for transport.

Lysosomes are membrane-bound vesicles containing digestive enzymes that function as intracellular digestive systems.
They are formed from the fusion of vesicles containing enzymes and materials to be broken down.

Microfilaments are small protein fibrils that provide structural support to the cytoplasm and contribute to cell shape and movement, particularly in muscle cells.
Intermediate filaments are larger than microfilaments and smaller than microtubules, providing additional structural support to the cell.

Mitochondria are organelles responsible for producing ATP through aerobic metabolism, with inner and outer membranes separated by an intermembrane space.
The inner membrane contains enzymes and mitochondrial DNA (mtDNA), and cells requiring high energy have more mitochondria.