Cell Biology and Structure

Mitochondria is known as the powerhouse of a cell. The energy required for various chemical activities needed for life is released by mitochondria in the form of ATP (Adenosine triphosphate) molecules.

A. The endoplasmic reticulum (ER) is a large network of membrane bound tubes and sheets. B. The function of the endoplasmic reticulum is to serve as channels for the transport of materials (especially proteins) between various regions of the cytoplasm or between the cytoplasm and the nucleus. C. In the liver cells of the group of animals called vertebrates, smooth endoplasmic reticulum plays a crucial role in detoxifying many poisons and drugs.

Plastids are small bodies found free in the cytoplasm of most plant cells. They are absent in bacteria, fungi, cyanobacteria.

P. Rough endoplasmic reticulum is specialised to synthesise proteins. Q. Some of the enzymes have been located in mitochondria, which helps in the synthesis of lipids like Lecithin from fatty acids and glycerol. R. Chloroplast stroma contains enzymes for conversion of carbon dioxide into carbohydrate. Lysosomes help in intracellular digestion of food particles.

The term 'mitochondria' was coined by Carl Benda in 1898. It is double membrane organelle of the cell. The functions of mitochondria are:

1. Mitochondria are described as the power house of a cell, and therefore is directed to the processes that evolve energy, mainly TCA, ETS, oxidative phosphorylation. All these three processes occur in mitochondria and result in the formation of energy compound called ATP.
2. Some of the enzymes have been located in mitochondria, which help in the synthesis of lipids like Lecithin from fatty acids and glycerol.
3. Mitochondria help in the transport of ATP. They collect at sites where energy requirement is high.
4. Due to the presence of RNA, DNA and ribosomes, proteins can be manufactured in mitochondria.
5. Mitochondria possess some of the enzymes of glyoxylate cycle. This cycle is modification of Kreb’s cycle in which fatty acids are converted into the carbohydrates. Endoplasmic reticulum was discovered and named so by Porter.

Leucoplasts are primarily organelles in which materials such as starch, oils and protein granules are stored. Lysosomes help in removing dead and worn out cellular organelles (cell debris) by digesting them.

A. Cells are enclosed by a plasma membrane composed of lipids and proteins. B. In plant cells, a cell wall composed mainly of cellulose is located outside the cell membrane. In animal cell the cell wall is mainly composed of phospholipids and proteins. C. The nucleus in eukaryotes is separated from the cytoplasm by double-layered membrane and it directs the life processes of the cell. D. Most plant cells have large membranous organelles called plastids, which are of two types- chromoplasts and leucoplasts. Chromoplasts that contain chlorophyll are called chloroplasts and they perform photosynthesis.

The functions of endoplasmic reticulum are: Detoxification: E.R helps in detoxification of many endogenous and exogenous compounds. Glycogenolysis: Synthesis of glycogen occurs in the cytoplasmic matrix but the SER is involved in glycogenolysis. Lipid synthesis: The SER is concerned with synthesis of lipid e.g. triglyceride. The membranes of SER also appear to be involved in the formation of lipoprotein complexes. The SER is also involved in the initial stages of the breaking down of fatty acids. The nucleoli present in the nucleus helps in the formation of ribosomes.

It contains digestive enzymes and it is surrounded by a membrane.

It is the ancient and simplest phenomena in which like molecules come closer to each other and results in the formation of microspheres, liposomes or coacervates.

Mitochondria are the powerhouses of the cell and the site of cellular respiration. They produce ATP through aerobic respiration using the Krebs cycle and electron transport chain. Endoplasmic reticulum handles protein synthesis, Golgi body modifies and packages proteins, and lysosomes digest waste - none of these perform cellular respiration.

The Golgi body (Golgi apparatus) produces vesicles that transport proteins and lipids to other destinations. It modifies, sorts, and packages materials into secretory vesicles. The nucleus doesn't produce vesicles. Mitochondria produce ATP through cellular respiration. Ribosomes synthesize proteins but don't produce vesicles.

Lysosomes are membrane-bound organelles containing digestive enzymes (hydrolases) that break down worn-out cell components, engulfed pathogens, and debris. This recycling process is called autophagy. Ribosomes synthesize proteins, centrioles aid in cell division, and cytosol is the fluid component of cytoplasm - none have digestive functions.

The cutting of DNA by restriction endonuclease results in the fragments of DNA. These fragments can be separated by a technique known as gel electrophoresis. DNA fragments are negatively charged molecules and can be separated by forcing them to move towards the anode under an electric field through a medium.

The cell walls are thin and made of cellulose.