BIOL 1406 Chapter 6 Cell Structure Lecture Slides PDF

Chapter 6 A Tour of the Cell  Cells  Cells were discovered in 1665 by Robert Hooke  The Cell Theory states: 1. All organisms are composed of cells 2. Cells are the smallest living things 3. Cells arise only from pre-existing cells  Mostcells are relatively small due to re...

Chapter 6 A Tour of the Cell  Cells  Cells were discovered in 1665 by Robert Hooke  The Cell Theory states: 1. All organisms are composed of cells 2. Cells are the smallest living things 3. Cells arise only from pre-existing cells  Mostcells are relatively small due to reliance on diffusion of substances in and out of cells  An organism made of many small cells has an advantage over an organism composed of fewer, larger cells! 2 Cell size is limited  As a cell’s size increases, its volume increases much more rapidly than its surface area  The neuron overcomes this limitation by being long and skinny! 3 Comparing Prokaryotic and Eukaryotic Cells Basicfeatures of ALL cells: ◦Plasma membrane ◦Semifluid substance called cytosol ◦Chromosomes (carry genes) ◦Ribosomes (make proteins)  Prokaryoti c Cells  Simplest organisms  Lack a membrane-bound nucleus (DNA is present in the nucleoid)  Cell wall outside of plasma membrane (protect the cell, maintain its shape, and prevent excessive uptake or loss of water)  Do contain ribosomes (not membrane-bound organelles)  Two domains of prokaryotes: Archaea and Bacteria 5 Eukaryotic Cells Possess a membrane-bound nucleus More complex than prokaryotic cells Hallmark is compartmentalization ◦ Achieved through use of membrane-bound organelles and endomembrane system  6 Check for Understanding Which of the following is a major cause of the size limits for certain types of cells? A. the evolution of larger cells occurred after the evolution of smaller cells B. the difference in plasma membrane structure between prokaryotes and eukaryotes C. Small cells have sufficient surface area to allow the cell to function efficiently in transporting substances across the membrane, and large cells do not D. the observation that longer cells usually have greater cell volume 7 Animal cell © 2021 Pearson Education, Inc. 8 Plant cell Video: https://www.youtube.com/watch?v=URUJD5NEXC8 9 Nucleus - Houses genetic information (chromatin: DNA + Protein) - Nucleolus: region where rRNA synthesis takes place - Nuclear Envelope 10 Ribosomes  Cell’s protein synthesis machinery  Found in all cell types  Ribosomal RNA (rRNA)-protein complex  Ribosomes may be free in cytoplasm or associated with internal membranes 11 The Endomembrane System Series of membranes throughout the cytoplasm in eukaryotic cells Includes the nuclear membrane, endoplasmic reticulum, Golgi, lysosomes, vesicles, and cell membrane Divides cell into compartments where different cellular functions occur One of the fundamental distinctions between eukaryotes and prokaryotes! 12  Endoplasmic Reticulum (ER)  Rough endoplasmic reticulum (RER) ◦ Contains ribosomes ◦ Synthesis of proteins to be secreted, sent to lysosomes or plasma membrane  Smooth endoplasmic reticulum (SER) ◦ Does not contain ribosomes ◦ Variety of functions (lipid synthesis, store calcium, detoxification) 13  Golgi Apparatu s  Flattened stacks of interconnected membranes (Golgi bodies)  Functions in packaging and distribution of molecules synthesized at one location and used at another location within/outside the cell  Cis and trans faces  Vesicles transport molecules to destination 14  Lysosomes  Membrane-bound digestive vesicles  Arise from Golgi apparatus  Enzymes catalyze breakdown of macromolecules  Destroy cells or foreign matter that the cell has engulfed by phagocytosis 15  Vacuoles  Membrane-bound structures in plants  Variousstorage functions depending on the cell type  Thereare different types of vacuoles: ◦ Central vacuole in plant cells ◦ Contractile vacuole of some protists ◦ Storage vacuoles 16  Mitochondria  Found in all types of eukaryotic cells  Bound by membranes ◦ Outer membrane ◦ Intermembrane space ◦ Inner membrane has cristae ◦ Matrix  On the surface of the inner membrane, and also embedded within it, are proteins that carry out oxidative metabolism (produce ATP)  Have their own DNA 17  Chloroplasts Organelles present in cells of plants and some other eukaryotes Contain chlorophyll for photosynthesis Surrounded by 2 membranes Thylakoids are membranous sacs within the inner membrane Have their own DNA 18 Endosymbi osis  Eukaryotic organelles evolved by symbiosis between two cells that were each free-living  One cell, a prokaryote, was engulfed by another cell, which was the precursor of modern eukaryotes  Mitochondria and Chloroplasts 19 Check for Understanding Which organelle is NOT part of the endomembrane system for transport? A. Endoplasmic reticulum B. Golgi apparatus C. Lysosomes D. Mitochondria 20 Cytoskeleton  Network of protein fibers found in all eukaryotic cells ◦ Supports the shape of the cell ◦ Keeps organelles in fixed locations  Dynamicsystem – constantly forming and disassembling 3 types of fibers: microtubules (thickest), microfilaments (thinnest; also called actin filaments), and intermediate filaments 21  Vesicle ATP  The Receptor for motor protein cytoskeleton interacts with Motor protein Microtubule motor proteins (ATP powered) of cytoskeleton to produce (a) motility Microtubule Vesicles  Insidethe cell, vesicles can travel along “monorails” provided by the cytoskeleton (b)  10 µm Column of tubulin dimers 25 nm   Tubulin dimer  Microtubules Comprise the Centrosomes Centrosome  Region surrounding centrioles in Microtubule almost all animal cells Centrioles  0.25 µm Microtubule- organizing center ◦ Can nucleate the assembly of microtubules  Animal cells and most protists have centrioles  Plants and fungi Longitudinal section of Microtubules Cross section one centriole of the other centriole lack centrioles  Cell Movement: Microtubules comprise flagella and cilia  Essentiallyall cell motion is tied to the movement of actin filaments, microtubules, or both  Flagella and cilia have 9 + 2 arrangement of microtubules  10 µm Actin subunit 7 nm  Microfilaments and Muscle Cells  Microfilaments that function in cellular motility contain the Muscle cell protein myosin in addition to Actin filament actin  In muscle cells, thousands of Myosin filament actin filaments Myosin arm are arranged parallel to one another (a) Myosin motors in muscle cell contraction  Thicker filaments composed of  Intermediate Filaments are comprised of Keratin proteins 5 µm Keratin proteins Fibrous subunit (keratins coiled together) 8–12 nm Check for Understanding This cellular component is not only responsible for the cell's shape and movement, but it also provides a scaffolding at certain locations of the cytoplasm for some enzymes and macromolecules: A. plasma membrane B. cytoskeleton C. nucleus D. muscle 29 Extracellular Components Most cells synthesize and secrete materials that are external to the plasma membrane These extracellular structures include: ◦ Cell walls of plants ◦ The Extracellular Matrix (ECM) of animal cells ◦ Intercellular junctions  Cell Walls of Plants  The cell wall is an extracellular structure Secondary cell wall that distinguishes plant Primary cells from animal cells cell wall  Prokaryotes, fungi, and Middle some protists also have lamella cell walls  The cell wall protects the plant cell, 1 µm maintains its shape, Central vacuole and prevents excessive Cytosol uptake of water Plasma membrane  Plant cell walls are Plant cell walls made of cellulose fibers embedded in other polysaccharides and protein Plasmodesmata  Polysaccharide Extracellular molecule Carbohydrates Matrix (ECM) Core protein  Animal cells lack cell walls  Secrete an elaborate mixture of Proteoglycan molecule glycoproteins into the space Proteoglycan complex around them  Collagen may be abundant  Form a protective layer over the cell surface  Integrins link ECM to cell’s cytoskeleton 32  Intercellular Junctions Tight junction  Neighboring Tight junctions prevent fluid from moving across a layer of cells cells often adhere, 0.5 µm interact, and communicate through Tight junction Intermediate direct filaments Desmosome physical Desmosome contact Gap junctions 1 µm  Intercellula Extracellular r junctions Space between matrix Gap cells junction facilitate this Plasma membranes contact 0.1 µm of adjacent cells