Passive Transport

Passive Transport

Passive Transport Plasma membranes must allow certain substances to enter and leave a cell, and prevent some harmful materials from entering and some essential materials from leaving. In other words, plasma membranes are selectively permeable—they allow some substances to pass through, but not others. If they were to lose this selectivity, the cell would no longer … Read more Passive Transport

Membrane Proteins

Membrane Proteins

Membrane Proteins Biological membranes consist of a continuous double layer of lipid molecules in which membrane proteins are embedded. Although the lipid bilayer provides the basic structure of biological membranes, the membrane proteins perform most of the membrane’s specific tasks and therefore give each type of cell membrane its characteristic functional properties. The amounts and … Read more Membrane Proteins

Membrane Lipids

Membrane Lipids

Membrane Lipids Biological membranes consist of a lipid bilayer to which proteins and carbohydrates may be associated or covalently linked. Membrane lipids are lipids involved in forming the structure of biological membranes – both the cell membrane and intracellular membranes – and in membrane function, namely compartmentalization of biological processes. Membrane lipids consist primarily of … Read more Membrane Lipids

Carbohydrates

Carbohydrates

Carbohydrates are molecules that contain carbon, hydrogen, and oxygen. There are twice as many hydrogen atoms as carbon or oxygen atoms. The general formula for a carbohydrate can be written as Cx(H2O)y. They act as the source of energy (e.g. glucose), as a store of energy (e.g. starch and glycogen) and as structural units (e.g. … Read more Carbohydrates

Active Transport- Types and Significance

Types of Active Transport

Active Transport- Types and Significance To sustain life, many substances need to be transported into, out of, and between cells. In some cases, this can be accomplished through passive transport, which uses no energy. In many cases, however, the cell needs to transport something against its concentration gradient. In these cases, active transport is required. Active transport mechanisms require … Read more Active Transport- Types and Significance

Digestion and Absorption of Carbohydrates, Proteins and Fats

Digestion and Absorption of Carbohydrates, Proteins and Fats

Digestion and Absorption of Carbohydrates, Proteins and Fats Carbohydrates, fats, and proteins are the major nutrients the body needs for growth, repair, movement and maintaining tissue and organ function. These macromolecules are broken down and absorbed into the body at different rates and into specific forms as they travel through the organs in the digestive … Read more Digestion and Absorption of Carbohydrates, Proteins and Fats

Heme Synthesis

Heme Synthesis Pathway

Heme Synthesis Hemes are cyclic tetrapyrroles that contain iron and are commonly found as the prosthetic group of hemoglobin, myoglobin and the cytochromes. Location of Heme Synthesis Heme synthesis takes place in the cytosol and mitochondria of cells of the liver and bone marrow. Substrates: Succinyl A CoA; glycine; Fe2+ Product: Heme. Overview of the … Read more Heme Synthesis

Heme Degradation

Heme Degradation

Heme Degradation Hemes are cyclic tetrapyrroles that contain iron and are commonly found as the prosthetic group of hemoglobin, myoglobin and the cytochromes. This small-molecule component of globins, critical for oxygen transport among other functions undergo a complex process of metabolism and degradation. Roughly 80% of heme destined for degradation and excretion comes from senescent … Read more Heme Degradation

Membrane Carbohydrate

Membrane Carbohydrate Structure

Membrane Carbohydrate Cell membranes are selective barriers that separate individual cells and cellular compartments. Membranes are assemblies of carbohydrates, proteins, and lipids held together by binding forces. Carbohydrates are covalently linked to proteins (glycoproteins) or lipids (glycolipids) and also an important part of cell membranes, and function as adhesion and address loci for cells. The Fluid Mosaic Model describes membranes as a … Read more Membrane Carbohydrate

Phosphoketolase (Heterolactic) Pathway

Phosphoketolase (Heterolactic) Pathway

Phosphoketolase (Heterolactic) Pathway The phosphoketolase pathway is distinguished by the key cleavage enzyme, phosphoketolase. Phosphoketolase in the pathway cleaves pentose phosphate into glyceraldehyde-3-phosphate and acetyl phosphate which is the prime reaction of the pathway. As a fermentation pathway, it is employed mainly by the heterolactic acid bacteria which carry out heterolactic fermentation. Heterolactic fermentation is a type of lactic acid fermentation in which … Read more Phosphoketolase (Heterolactic) Pathway