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  2. • The nuclear envelope, like the cell membrane, is too thin to be appreciated under the optical microscope, but it is visible in EM. • It consists of two unit membranes; • *Outer nuclear membranes • *Inner nuclear membranes • 7 to 8nm thick each, that are separated from each other by a 10 to 30nm fluid-filled space (perinuclear space; perinuclear cisterna; intermembranous space).
  3. The nuclear envelope is perforated by circular openings (nuclear pores) that are 70 to 75nm in diameter. • Each nuclear pore is ringed by a nuclear pore complex that is made up of electron-dense protein molecules. Some of the proteins in the nuclear pore complex form a thin film, called pore diaphragm, which covers the nuclear pore.
  4. Chromatin (Chromatin material; chromatin threads) • Chromatin – refers to the chromosomes at interphase. • The nucleus of all nucleated human cells contain 46 chromosomes (22 pairs of somatic and pair of sex chromosomes). Cells with 46 chromosomes are referred to as diploid while those with only 23 are referred to as haploid.
  5. • Each chromosome consists of one very long DEOXYRIBONUCLEIC ACID (DNA) MOLECULE and a variety of associated proteins (nucleoproteins). The nucleoproteins are of two major types, histones and nonhistones.
  6. HUMAN GENOME -Refers to the total amount of DNA that is present in a human cell. - It consists of of a large chromosomal genome, which refers to the DNA in chromosomes and much smaller mitochondrial genome which refer, to the DNA in the mitochondria. ( The only cellular structures aside from the nucleus that contain DNA).
  7. NUCLEAR MATRIX ( Nuclear sap; Nucleoplasm) • Nuclear matrix is composed of water, proteins, metabolites, and ions. The proteins that are present in the nuclear matrix are mostly associated with DNA molecules.
  8. NUCLEOLUS • The nucleolus is a spherical, highly basophilic structure that is usually eccentrically located in the nucleus. It is not enveloped by unit membrane and is present only in the cells that are at interphase.
  10. PROTEIN SYNTHESIS WITHIN THE CELL One of the most important activities of a cell is the production or synthesis of proteins. Proteins comprise many essentials parts of cells and tissues. They likewise make up the enzymes that catalyze biochemical reactions, and hormones and hormone- like substances that regulate the activity of cells.
  11. MOVEMENT OF MATERIALS ACROSS THE CELL MEMBRANE • The cell membrane is a semi-permeable barrier, which means that it allows certain materials to enter and leave the cell while it constrains others. • Simple molecules cross the cell membrane by a variety of means : diffusion ; passage through ion channels : carrier transport: and active transport with the aid of pumps. These methods of transport are described in physiology textbooks. Bigger substances such as bacteria and secretory products, on the products, are carried across the cell membrane via two mechanisms ;
  12. • Endocytosis – refers to transport of substances from the extracellular space into the cell. If the substance being transported is solid such as a bacterium or dust particle, the process is called phagocytosis, but if it is liquid, the process is called pinocytosis. • It simply involves invagination of the cell membrane to enclose the fluid that needs to be ingested and then pinching off of the membrane-bound pinocytic vesicle from the inner surface of the cell membrane. • Pinocytosis that involves intake of large amounts of liquids is called macropinocytosis while pinocytic intake of minute amounts of liquid is referred to as micropinocytosis.
  13. • EXOCYTOSIS • - Exocytosis refers to the process of transporting substances that are inside the cell, mostly secretory products (secretions) which are in form of secretory vesicles from the Golgi complex, across the cell membrane and out of the cell. It involves fusion of the vesicular membrane with the cell membrane followed by the release of vesicular contents to the exterior of the cell. • Exocytotic release of secretory products by cells occurs in either one of two ways; regulated secretion or constitutive secretion.