* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download 03 Eukaryotic cell structure
Survey
Document related concepts
Tissue engineering wikipedia , lookup
Cytoplasmic streaming wikipedia , lookup
Cell encapsulation wikipedia , lookup
Extracellular matrix wikipedia , lookup
Cellular differentiation wikipedia , lookup
Programmed cell death wikipedia , lookup
Cell growth wikipedia , lookup
Cell culture wikipedia , lookup
Signal transduction wikipedia , lookup
Cell membrane wikipedia , lookup
Organ-on-a-chip wikipedia , lookup
Cytokinesis wikipedia , lookup
Cell nucleus wikipedia , lookup
Transcript
Cell is the base of life 5/24/2017 How can one define life? The simplest definition is that any living thing must have three general properties: • metabolism • growth • reproduction 5/24/2017 Life's Hierarchy Life on Earth is incredibly extensive and, to make it easier to study, biologists have broken living systems up into generalized hierarchical levels: molecules; organells; cells; tissues; organs; organisms; populations 5/24/2017 Life's Hierarchy The focus of this course is on the fundamentals of life; that is, the properties that are held in common among all living things. We will concentrate almost exclusively on the molecular through the cellular level. 5/24/2017 The cell theory 1. Cells are the fundamental units of life, because a cell is the simplest unit capable of independent existence. 2. All living things are made of cells. Mattias Schleiden and Theodor Schwann (1839) called cells “units of life” – cell theory. This theory still holds true, with the minor caveat that viruses are only alive while infecting a cell. 5/24/2017 Cell elemental composition Cells are 90% water. The remaining molecules, the dry weight is approximately: • 50% protein • • 15% carbohydrate • 15% nucleic acid • 10% lipid • 10% miscellaneous 5/24/2017 Similarities between the pro- and eukaryotic types of cells 1. They both have DNA as their genetic material. 2. They are both membrane bound. 3. They both have ribosomes. 4. They have similar metabolism. 5/24/2017 Major differences 1. Eukaryotes have a nucleus and membrane-bound organelles, while prokaryotes do not. 2. Prokaryotic DNA floats freely around the cell; eukaryotic is held within its nucleus. 3. Eukaryotic/prokaryotic size is 10/1. 4. The DNA of eukaryotes is much more complex. 5. Prokaryotes have a cell wall composed of peptidoglycan, a polymer of amino acids and sugar. Some eukaryotic cells also have cell walls, but none made of peptidoglycan. 5/24/2017 Eukaryote cells (protozoa, fungi, higher animals and plants) Each eukaryote has •a surrounding membrane - a thin layer of protein and fat that restricts the flow of substances in and out of the cell and encloses the •cytoplasm, a jellylike material containing the nucleus and other structures (organelles) such as mitochondria. •the nuclei of some cells contain a dense spherical structure called the nucleolus, which contains ribonucleic acid (RNA) for the synthesis of ribosomes. 5/24/2017 Animal cell structure 5/24/2017 Liver cell 5/24/2017 Liver cell nucleus and nucleolus 5/24/2017 Plant cell structure The plant cell is surrounded by: a plasma membrane and contains: a nucleus, ribosomes, ER, Golgi apparatus, mitochondria, peroxisomes, microfilaments and microtubules. 5/24/2017 Plant cell structure Plant cell also contains a family of membraneenclosed organelles called plastids. The most important type of plastid is the chloroplast, which carries out photosynthesis, converting sunlight to chemical energy stored in sugar and other organic molecules. 5/24/2017 Plant cell structure Another prominent organelle in many plant cells, especially older ones, is a large central vacuole. The vacuole stores chemicals, breaks down macromolecules, and, by enlarging, plays a major role in plant growth. 5/24/2017 Plant cell structure The vacuole membrane is called the tonoplast. Outside a plant cell's plasma membrane (in fungi and some protists as well) is a thick cell wall. 5/24/2017 Plant cell structure It helps to maintain the cell's shape and protects the cell from mechanical damage. The cytosol of adjacent cells connects through trans-wall channels called plasmodesmata. 5/24/2017 Nucleus structure 5/24/2017 The nuclear envelope 5/24/2017 Nucleus with Nuclear Pores 5/24/2017 Ribosomes Ribosomes are the sites of protein synthesis. They are not membrane-bound and thus occur in both prokaryotes and eukaryotes. Eukaryotic ribosomes are slightly larger than prokaryotic ones. 5/24/2017 Ribosomes Structurally the ribosome consists of a small and larger subunit. Biochemically the ribosome consists of ribosomal RNA (rRNA) and some 50 structural proteins. Often ribosomes cluster on the endoplasmic reticulum, in which case they resemble a series of factories adjoining a railroad line. 5/24/2017 Structure of the ribosome Small subunit Large subunit 5/24/2017 Ribosomes Both free and bound ribosomes are abundant in this pancreas cell (TEM). The pancreas secretes hormones, including the protein insulin, into the bloodstream, and secretes digestive enzymes into the intestine. 5/24/2017 Ribosomes Bound ribosomes, those presently attached to the endoplasmic reticulum (ER), produce secretory proteins. Free ribosomes mainly make proteins that will remain dissolved in the cytosol. Bound and free ribosomes are identical and can alternate between these two roles. 5/24/2017 Ribosomes and Polyribosomes in liver cell 5/24/2017 The Endomembrane system A membranous system of interconnected tubules and cisternae Membranes of the endomembrane system vary in structure, composition, thickness and behavior The endomembrane system includes: Nuclear envelope Endoplasmatic reticulum Golgi apparatus Lysosomes Vacuoles Plasma membrane (related to endomembrane) 5/24/2017 The Endomembrane system A membranous system of interconnected tubules and flattened sacs called cisternae, the ER is also a continuous with the nuclear envelope. The membrane of the ER encloses a compartment called the cisternal space. Rough ER, which is studded on its outer surface with ribosomes, can be distinguished from smooth ER in the electron micrograph (TEM). 5/24/2017 The Endomembrane system Endoplasmic reticulum is a mesh of interconnected membranes that serve a function involving protein synthesis and transport. Membranes in the endomembrane system are related either through: -direct physical continuity or -by the transfer of membrane segments as tiny vesicles. 5/24/2017 Endoplasmatic reticulum (ER) cisternae cisternal space rough ER ribosomes smooth ER 5/24/2017 Endoplasmatic reticulum Rough endoplasmic reticulum (Rough ER) is so-named because of its rough appearance due to the numerous ribosomes that occur along the ER. Rough ER connects to the nuclear envelope through which the messenger RNA (mRNA) that is the blueprint for proteins travels to the ribosomes. 5/24/2017 Rough ER Newly synthesized proteins fold into its native conformation Most of the secretory proteins are glycoproteins (proteins covalently bound to carbohydrates Secretory proteins are kept separate from the other proteins to be remained in cytosol Secretory proteins leave the ER in transport vesicles 5/24/2017 Rough ER Another very important function of rough ER is the “production of the membrane” Proteins and phospholipids are added to the membrane They are either transported to rough ER or synthesized in rough ER (phospholipids) 5/24/2017 Smooth ER Smooth ER lacks the ribosomes characteristic of Rough ER and is thought to be involved in transport and metabolic processes including: •synthesis of lipids (phospholipids and steroids), •metabolism of carbohydrates, and •detoxification of drugs and poisons 5/24/2017 Smooth ER Among the steroids produced by SER are: the sex hormones secreted by the adrenal glands; testes and ovaries are rich in smooth ER Role of smooth ER in carbohydrate metabolism is well presented by liver cells: liver cells store carbohydrate in the form of glycogen; phosphate molecule is removed from the glucose which can then live the cell 5/24/2017 Smooth ER Detoxification of drugs in liver cells mainly occur by adding hydroxyl groups to drugs. Hydroxylation makes drugs more soluble and more easier to flush from liver cells Unfortunately the exposure to barbiturates or alcohol forces the growth of smooth ER and subsequent increase tolerance to one of these agents 5/24/2017 Summary 5/24/2017 Summary 5/24/2017 Reading Campbell et al. Biology. Ch. 6 A tour of the cell, 110-107. 5/24/2017