Notes

A cell is composed of a lot of parts but if we are forced to divide it into 3 parts, I'd pick the cell membrane, the nucleus, and cytoplasm. The cell (plasma) membrane separates each cell from the environment, permits the flow of molecules across the membrane, and contains receptors that can affect the cell’s activities. It provides overall rigidity and shape to the cell. It also protects the cell from external harmful agents like bacteria, viruses, etc. The nucleus, A DNA-containing region that occupies a portion of the interior. It determines how the cell will function, as well as the basic structure of that cell. The cytoplasm is the gel-like fluid inside the cell containing some important parts like mitochondria, Golgi bodies, robustness, etc. Thus most of the chemical reactions of a cell take place here. 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.
Plant and animal cells have many of the same organelles. But in some cases, the organelles in cells are different. For example, in plant cells, more types of organelles are found in animal cells. Below are some of the commonly found subcellular organelles in cells.
Channels/pores- A channel in the cell's plasma membrane. This channel is made up of certain proteins that control the movement of molecules, including food and water, into the cell.
Endoplasmic reticulum (ER)- It is a network of membranes throughout the cytoplasm of the cell. There are two types of ER. When ribosomes are attached it is called rough ER and smooth ER when there are no ribosomes attached. The rough endoplasmic reticulum is where most protein synthesis occurs in the cell. The function of the smooth endoplasmic reticulum is to synthesize lipids in the cell. The smooth ER also helps in the detoxification of harmful substances in the cell.
Ribosomes- Organelles that help in the synthesis of proteins. Ribosomes are made up of two parts, called subunits. Ribosomes are made of one large and one small subunit. They get their names from their size. One unit is larger than the other so they are called large and small subunits.
Both these subunits are necessary for protein synthesis in the cell. When the two units are docked together with a special information unit called messenger RNA, they make proteins. Some ribosomes are found in the cytoplasm, but most are attached to the endoplasmic reticulum. While attached to the ER, ribosomes make proteins that the cell needs and also ones to be exported from the cell for work elsewhere in the body.
Golgi complex- It is the organelle in the cell that is responsible for sorting and correctly shipping the proteins produced in the ER. Just like our postal packages, which should have a correct shipping address, the proteins produced in the ER should be correctly sent to their respective address. It is a very important step in protein synthesis. If the Golgi complex makes a mistake in shipping the proteins to the right address, certain functions in the cell may stop.
Mitochondrion- This is the cell’s powerhouse. This organelle packages the energy from the food you eat into ATP molecules. Every type of cell has a different amount of mitochondria (plural). There are more mitochondria in cells that have to perform lots of work, for example- your leg muscle cells, heart muscle cells etc. Other cells need less energy to do their work and have fewer mitochondria.
Chloroplast- This is the organelle in which takes photosynthesis place. In this organelle, the light energy of the sun is converted into chemical energy. Chloroplasts are found only in plant cells, not animal cells. The chemical energy that is produced by chloroplasts is finally used to make carbohydrates like starch that get stored in the plant. Chloroplasts contain tiny pigments called chlorophylls. Chlorophylls are responsible for trapping the light energy from the sun.
Vesicles- This term literally means "small vessel". This organelle helps store and transport products produced by the cell. The vesicles are the transport and delivery vehicles like our mail and Federal Express trucks. Some vesicles deliver materials to parts of the cell and others transport materials outside the cell in a process called exocytosis.
Vacuole- Plant cells have what looks like a very large space in the middle. This space is called the vacuole.
Cell wall and Plasmodesmata- In addition to cell membranes, plants have cell walls. Cell walls provide protection and support for plants. Inland plants, the cell wall is mostly made of cellulose. Unlike cell membranes, materials cannot get through cell walls. This would be a problem for plant cells if not for special openings called plasmodesmata. These openings are used to communicate and transport materials between plant cells because the cell membranes can touch and therefore exchange needed materials.
Peroxisomes- These collect and safely break down chemicals that are toxic to the cell.
Centrioles- These are found only in animal cells and come into action when the cells divide, helping with the organization of chromosomes.
Lysosomes- Created by the Golgi apparatus, this help break down large molecules into smaller pieces that the cell can use.
Cytoskeleton- Made up of filaments and tubules, it helps shape and supports the cell. It also helps move things move around in the cell. For artistic purposes, the cytoskeleton is shown in just one place when in reality it is found throughout the entire cell.