explain all parts of cytoplasmic organelles
Answers
Cell membrane
Every cell in the body is enclosed by a cell (Plasma) membrane. The cell membrane separates the material outside the cell, extracellular, from the material inside the cell, intracellular. It maintains the integrity of a cell and controls passage of materials into and out of the cell. All materials within a cell must have access to the cell membrane (the cell's boundary) for the needed exchange
Nucleus and Nucleolus
The nucleus, formed by a nuclear membrane around a fluid nucleoplasm, is the control center of the cell. Threads of chromatin in the nucleus contain deoxyribonucleic acid (DNA), the genetic material of the cell. The nucleolus is a dense region of ribonucleic acid (RNA) in the nucleus and is the site of ribosome formation. The nucleus determines how the cell will function, as well as the basic structure of that cell.
Cytoplasm
The cytoplasm is the gel-like fluid inside the cell. It is the medium for chemical reaction. It provides a platform upon which other organelles can operate within the cell. All of the functions for cell expansion, growth and replication are carried out in the cytoplasm of a cell. Within the cytoplasm, materials move by diffusion, a physical process that can work only for short distances.
Mitochondria
An eukaryotic cell contains many mitochondria, occupying up to a quarter of the cytoplasmic volume. The size of a mitochondrion is about 1.5-2 μm in length, 0.5-1 μm in diameter, approximately the same as E. coli. It has two membranes: outer membrane and inner membrane. Mitochondria also have their own DNA (represented as mtDNA), which encodes some of the proteins and RNAs in mitochondria. However, most proteins operating in mitochondria still originate from nuclear DNA.
Chloroplasts
Like mitochondria, a chloroplast also contains both outer and inner membranes on its surface. Inside the chloroplast, there are many thylakoids, each is enclosed by a membrane. Chlorophylls are located on the thylakoid membrane to absorb light for photosynthesis.
Endoplasmic reticulum
Endoplasmic reticulum (ER) can be divided into rough ER and smooth ER. The major role of rough ER is to process the newly synthesized peptides from ribosomes. Therefore, the surface of rough ER is usually associated with ribosomes and thus appears "rough". Smooth ER is involved in the synthesis and metabolism of lipids. Hepatocytes are abundant in smooth ER.
Golgi apparatus
Golgi apparatus is a major site for sorting and modifications of proteins and lipids. After proteins are sorted at rough ER, they are enclosed in transport vesicles and carried to the Golgi apparatus. Some proteins could be modified into glycoproteins and then transported to other destinations.
Lysosomes
The major function of lysosomes is to degrade various macromolecules in the cell. They contain nuclease for degrading DNA and RNA, protease for degrading proteins and other enzymes for degrading polysacchrides and lipids. Lysosomes exist only in animal cells. Although plant cells do not have lysosomes, their vacuoles are also capable of degrading macromolecules.
Vacuoles
Vacuoles store small molecules such as water, ions, sucrose and amino acids. They can also hold waste products which will be slowly degraded. They typically occupy more than 30% of the cell volume, but may expand up to 90%.