Cell Biology and Structure

They are of three types. Actin filaments, microtubules,and intermediate filaments,  they provide structure and organization to the cytoplasm and shape to the cell. They are of three types - Actin filaments, microtubules,and intermediate filaments. They provide structure and organization to the cytoplasm,  and shape to the cell.

Stem cells are undifferentiated biological cells that can differentiate into specialized cells and can divide (through mitosis) to produce more stem cells.

In placental mammals, the umbilical cord is a conduit between the developing embryo or fetus and the placenta.

Oxidative phosphorylation is the process in which ATP is formed. This process, which takes place in mitochondria, is the major source of ATP in aerobic organisms.

Mammalian erythrocytes have short life span due to absence of nucleus.

 Sieve tubes are living and non–nucleated at maturity.The main function of the sieve tube is transport of carbohydrates, primarily sucrose, in the plant (e.g., from the leaves to the fruits and roots).

 Vessels do not have end walls.The cells are arranged in longitudinal series in which the partitioned walls (transverse walls) are perforated, so the entire structure looks-like a water pipe. Their main function is transport of water and minerals. It also provides mechanical strength.

Each tissue consists of cells, which are similar in origin and form, and perform the same function. 

 A tissue is a group of cells having similar structure and function.Organs are then formed by the functional grouping together of multiple tissues.

The variety of tissue using the greatest amount of energy in a living system is muscular tissue. Muscles store energy for their own use in the form of glycogen, which represents about 1% of their mass. Glycogen can be rapidly converted to glucose when more energy is necessary.

 Blood is a type of connective tissue for two basic reasons: (1) embryologically, it has the same origin (mesodermal) as do the other connective tissue types and (2) blood connects the body systems together bringing the needed oxygen, nutrients, hormones and other signaling molecules, and removing the wastes.

Tracheids are elongated cells in the xylem of vascular plants that serve in the transport of water and mineral salts. Tracheids are one of two types of tracheary elements, vessel elements being the other.

Neuron is the longest cell of an animal's body. A neuron is an electrically excitable cell that processes and transmits information through electrical and chemical signals.

Krebs' cycle occurs in the mitochondria.

Astrocytes have many cytoplasmic processes terminating on blood vessels. These cells are engaged in all essential CNS functions including blood flow regulation, maintaining the blood brain barrier, energy metabolism, ion and water homeostasis, immune defence of the body, etc.