Bulk Transport cell eating cell drinking Active Transport Highly specific! Bulk transport is the active intracellular membrane transport of large numbers of solute particles or a large volume of solution forming a vacuole or vesicle. It is a form of active transport because it requires ATP (not shown). Endocytosis ( inside cell ) generally refers to intracellular bulk transport. Phagocytosis ( cell eating ) is bulk transport involving pseudopodia surrounding and engulfing large extracellular particles (food) forming a phagocytic vacuole. Pinocytosis ( cell drinking ) is bulk transport involving the engulfment of extracellular solution by infolding the plasma membrane forming a vesicle. Receptor-mediated endocytosis is bulk transport involving infolding of the plasma membrane lined with extracellular solute specific receptors and intracellular coat proteins forming a coated vesicle. The contents of a phagocytic vacuole will be Digested and diffuse into the cytosol. The contents of a pinocytotic vesicle will diffuse into the cytosol. The contents of a coated vesicle will be delivered to an intracellular location specified by the coat proteins (like an address). Plasma membrane actively engulfs large quantities! 22
Bulk Transport Active Transport Exocytosis ( outside cell ) is active extracellular bulk transport involving the fusion of transport vesicles with the plasma membrane, emptying their contents outside the cell. When the cell is specialized to manufacture and release compounds through exocytosis, it is known as secretion. For example the secretion of hormones from endocrine glands. The ER might produce proteins for exocytosis? In this process, the golgi receives the contents of the transport vesicle and repackages it in a secretory vesicle. This series of organelles are part of the endomembrane system? The secretory vesicle membrane adds to and becomes part of the plasma membrane. Plasma membrane actively secretes large quantities! 23
Unicellular Organisms The Diversity of Cellular Life The organism in the TEM is a spirilli Eubacteria, indicated by its small size. Is it microscopic, again indicated by its small size and use of a TEM. It is unicellular, as all bacteria are, indicated by not seeing multiple cells. Because they are microscopic, unicellular organisms collectively known as microorganisms (microbes). The Kingdoms that include unicellular organisms are: Archaebacteria, Eubacteria, most Protista, & some Fungi. Microorganisms dominate life on Earth, especially prokaryotes (bacteria)! 10µm Colorized TEM We live within the system setup and run by microbes! 24
Multicellular Organisms The Kingdoms that include multicellular organisms are some Protista, most Fungi, Plantae, and Animalia. The Diversity of Cellular Life This is a photo of a fertilized egg (zygote) completing its first cleavage (division) to become an embryo. A short time before this photo was taken, there would have been only one cell (zygote). This is how all multicellular organisms start out! These cells will continue to divide and develop from an embryo to a fetus, as cells differentiate and become specialized to function within the tissues, organs and organ systems of the organism. All multicellular organisms have common ancestry with (arose from) unicellular organisms of the Kingdom Protista! We all developed from one cell that divided and differentiated! 25
Differentiation & Specialization Multicellular Organisms Red Bood Cells Muscle Cells Pancreatic Cell Cell differentiation is the process during multicellular development by which cells become different from other cells, eventually expressing only a specific 30% of their genes. Cell specialization is the result of cell differentiation where different cell types have unique structure to perform specialized functions in specialized tissues, organs and organ systems. Red blood cells are specialized to be packed full of hemoglobin (no nucleus) so they can carry as much oxygen as possible. Muscle cells are packed full of contractile proteins (visible striations) so they can contract (shorten). Pancreatic cells are glandular, specialized to secrete specific protein enzymes and hormones (blue secritory vesicles). We are made up of over 200 specialized cell types! 26
Differentiation & Specialization Multicellular Organisms This micrograph shows the epithelium (outer covering) of a leaf. The small openings are stomata (singular, stomate). The two cells on either side of each opening are called guard cells. Guard cells are specialized to regulate the opening and closing of the stomate. Stomate This regulates gas exchange in the plant (CO 2 in, O 2 out) and the rate of transpiration (H 2 O out, drawing everything up from the roots). Guard cells All multicellular organisms have specialized cells! 27
7-4 The Diversity of Cellular Life Levels Of Multicellular Organization (Hierarchy of Biological Organization) Muscle cell Smooth muscle tissue Stomach Digestive system Level & Definition Level & Definition Level & Definition Cellular Level - A cell Tissue Level - A Organ Level - A is the basic unit of group of specialized collection of life, structure & cells functioning specialized tissues function. A plasma together to perform a functioning together membrane enclosing specialized function to perform a cytoplasm including as part of an organ. specialized function DNA and specialized as part of an organ organelles. system. Level & Definition Organ System Level - A collection of specialized organs functioning together to perform a specialized life function as part of an organism. 1. Cardiac Cell (Heart) 1. Cardiac Muscle 1. Heart 1. Circulatory 2. Skin Cell 2. Epithelial Tissue 2. Skin 2. Integumentary 3. Tubule Cell 3. Proximal Tubule 3. Kidney 3. Excretory 4. Primary Oocyte 4. Follicular Tissue 4. Ovary 4. Reproductive 28