abida Archive


Lyso ome is a membrane-enclosed bag of hydrolytic enzymes that the cell uses to digest macromolecules. The lysosomal enzymes can hydrolyze prote ns. polysaccharides, fats, and nucleic acid. These enzymes work best in acidi environment at about pH 5. The lysosomal membrane maintains this


The Golgi apparatus consists of flattened membranous sacs. They look like a stack of pita bread. A cell may have several interconnected stacks. Each cisterns in a stack consists of a membrane. This membrane separates its internal space from the cytosol. Vesicles concentrated near


The word endoplasmic means “within” the cytoplasm. The word reticulum means “network.” The ER consists of a network of membranous tubules and sacs called cisternae. The ER are extensive in the cell. They are composed of more than half of the total membrane in


Ribosomes are non-membranous bounded strOctures. Ribosomes are the sites where the cell synthesizes proteins according to genetic instructions. A bacterial cell may have a few thousand ribosomes.But a human liver cell has a few million ribosomes. Cells hat have high protein synthesis have a


CYTOPLASM The cytoplasm of a cell has two distinct parts: The Cytomembrane system: It consists of well-defined structures, such as endoplasmic reticulum, Golgi apparatus. vacuoles, and vesicles. The fluid cytosol: It suspends the structures of the cytomembrane system. Italso contains various dissolved molecules.

Movement of membrane across plasma membrane

      greater than it inside. Filtration Hydrostatic       pressure     forces     small molecules            across            selectively permeable membranes from areas of higher    pressure     to   areas    of    lower pressure. A frog’s blood         pressure forces           water          and dissolved wastes into the kidney        tubules      during urine formation. Active


Molecules can cross membranes in a-number of ways. They may use their own energy. Or they rely on an outside energy source. There are following types of cell movements. SIMPLE DIFFUSION Th movement of molecules from the area of higher concentration to the ar


The plasma membrane surrounds the cell. Chemically plasma membrane is composed of: Protein: 60 to 80% Phospholipids: 20 to 40 % Cholesterol in small amount Carbohydrates in small amount Fig: Fluid mosaic model of plasma membrane STRUCTURE OF CELL MEMBRANE S. onathan Singer and


Multiple Choice Questions MCQs Four options are given at the end of each statement. You should encircle one option from them. The number of electrons present in nature are: (a) 57               (b) 87                           (c) 92                           (d) 97 Carbon, hydrogen, oxygen, and nitrogen forms: (a)