#1.3 Cell Theory - Membrane Structure

In this sub-unit of IB biology, we are going to explain the shortest part of unit 1, we are going to understand the concepts of: Cells can only be formed by division of pre-existing cells The first cells must have arisen from non-living material The origin of eukaryotic cells can be explained by the endosymbiotic theory

In today's podcast we are going to explore and understand the concepts of: Particles move across membranes by simple diffusion, facilitated diffusion, osmosis and active transport The fluidity of membranes allows materials to be taken into cells by endocytosis or released by exocytosis Vesicles move materials within cells

In this sub-unit we are going to explore the concepts and understanding of: Understandings: Phospholipids form bilayers in water due to the amphipathic properties of phospholipid molecules Membrane proteins are diverse in terms of structure, position in the membrane and function Cholesterol is a component of animal cell membranes

In this second part of unit 1 of the IB biology, we will explore the concepts of: Prokaryotes have a simple cell structure without compartmentalization Eukaryotes have a compartmentalized cell structure Electron microscopes have a much higher resolution than light microscopes

Welcome everyone in the first episode of this podcast we are going to understand the key concepts of the first part of IB biology which are: According to the cell theory, living organisms are composed of cells Organisms consisting of only one cell carry out all the functions of life in that cell Surface area to volume ratio is important in the limitation of cell size Multicellular organisms have properties that emerge from the interaction of their cellular components Specialized tissues can develop by cell differentiation in multicellular organisms

In the last sub-unit of unit 6 we are going to explore the content of: Insulin and glucagon are secreted by β and α cells of the pancreas respectively to control blood glucose concentration Thyroxin is secreted by the thyroid gland to regulate the metabolic rate and help control body temperature Leptin is secreted by cells in adipose tissue and act on the hypothalamus of the brain to inhibit appetite Melatonin is secreted by the pineal gland to control circadian rhythms A gene on the Y chromosome causes embryonic gonads to develop as testes and secrete testosterone

In this sub-unit of unit 6, we are ging to synthesize and explain the contents such as: Neurons transmit electrical impulses The myelination of nerve fibers allows for saltatory conduction Neurons pump sodium and potassium ions across their membranes to generate a resting potential An action potential consists of depolarization and repolarization of the neuron Nerve impulses are action potentials propagated along the axons of neurons

In this sub-unit we are going to explore the contents of: Understandings: Ventilation maintains concentration gradients of oxygen and carbon dioxide between air in alveoli and blood flowing in adjacent capillaries Air is carried to the lungs in the trachea and bronchi and then to the alveoli in bronchioles Type I pneumocytes are extremely thin alveolar cells that are adapted to carry out gas exchange Type II pneumocytes secrete a solution containing surfactant that creates a moist surface inside the alveoli to prevent the sides of the alveolus adhering to each other by reducing surface tension

In this sub-unit we are going to explore contents of: The skin and mucous membranes form a primary defence against pathogens that cause infectious disease Cuts in the skin are sealed by blood clotting Clotting factors are released from platelets The cascade results in the rapid conversion of fibrinogen to fibrin by thrombin

In this sub-unit of human physiology we will explore contents of: Arteries convey blood at high pressure from the ventricles to the tissues of the body Arteries have muscle cells and elastic fibres in their walls The muscle and elastic fibres assist in maintaining blood pressure between pump cycles Blood flows through tissues in capillaries Capillaries have permeable walls that allow exchange of material between cells in the tissue and the blood in the capillary Veins collect blood at low pressure from the tissues of the body and return it to the atria of the heart Valves in veins and the heart ensure circulation of blood by preventing backflow