SBI3U7 Cell Structure & Organelles 2.2 Prokaryotic Cells 2.3 Eukaryotic Cells
No nucleus Prokaryotic Cells No membrane bound organelles Has a nucleus Eukaryotic Cells Membrane bound organelles Unicellular Unicellular or multicellular Naked circular DNA, no chromosomes DNA associated with proteins, wound into chromosomes No mitochondria Mitochondria for respiration 70s ribosomes 80s ribosomes ie Bacteria like E. coli ie cells found in animal, plant and fungi 2
Prokaryotic Cell
Cilia and Flagella Both are made of fine protein fibres Both can be used for locomotion Cilia: short, may be numerous on cell surface Flagella: long, usually few in number on cell surface Pili: used for attachment to other bacteria (used in sexual reproduction)
Prokaryotic Cells divide by binary fission
Structure and Function of Organelles The Structure and Function of the following organelles will be discussed: Cell Membrane Nucleus Cell Wall Cytoplasm Cytoskeleton Ribosomes Endoplasmic Reticulum Golgi Apparatus Mitochondria Lysosomes Cilia and Flagella Centrioles Vacuoles Plastids
Plant Cell Electron micrograph of a typical plant cell Note: mitochondria in red, nucleus in green, plastids in yellow
Animal Cell Electron micrograph of a typical animal cell Note: mitochondria in red, nucleus in peach, endoplasmic reticulum in blue
Animal vs. Plant Cell 9
Nucleus Directs all activities of the cell Electron micrograph of a nucleus Note: nucleolus in center of nucleus, endoplasmic reticulum and ribosomes just outside of nucleus
Components of the Nucleus Nucleolus: a dense area within the nucleus; the location for production of ribosomes Chromatin: stringy material made of proteins and DNA that takes up the majority of the nucleus Nuclear Envelope: double-layered membrane surrounding the nucleus. Contains nuclear pores to allow material to pass in and out. Chromosomes: condensed chromatin; just before the cell begins to divide the chromatin condenses into chromosomes
Endoplasmic Reticulum The ER is a twisting network of canals and sacs extending through the cytoplasm and connecting the cell membrane to the nuclear membrane The ER may have ribosomes attached to it (rough ER) The ER serves to transport products (e.g. proteins) within the cell
Rough vs. Smooth ER rer ser Contain many ribosomes Contains many enzymes Protein synthesis Multiple functions (in liver cells, breaks down toxins) Also produces phospholipids (used in construction of membranes) 13
Golgi Apparatus The Golgi apparatus are sacs of membranous plate-like bags which produce vesicles (sacs) They function to produce and store cellular secretions Many proteins and lipids undergo final processing in the Golgi apparatus
Mitochondria Mitochondria are the site of aerobic cellular respiration Cellular respiration is the process that converts sugar energy into adenosine triphosphate (ATP) for storage (overall reaction: sugar + O 2 CO 2 + H 2 O + ATP energy) ATP is used by other organelles & cell processes for energy Cells that respire rapidly (like muscle cells) have numerous mitochondria
Mitochondrial structures Cristae: site of chemical reactions using embedded proteins (greatly increase the surface area) Matrix: mitochondrion cytosol Mitochondrial DNA: self replicating organelle, produces its own unique proteins
Lysosomes Membrane bound sacs that are used for digestion of various structures within the cell An acidic environment along with hydrolytic enzymes within lysosomes help to digest particles Usually not in plant cells
Exam Question (a) Identify the structures labelled I and II. (2) (b) State one function of the structure labelled II. (1) (c)deduce, with a reason, whether this cell is eukaryotic or prokaryotic. (1) (Total 4 marks)
Mitochondrion Exam Question Example #7 Markscheme I: membrane / (nuclear) envelope II: mitochondrion / mitochondria Function of mitochondrion (II): aerobic respiration; correct specific reaction / pathway occurring in mitochondria / ATP production; Do not accept energy production alone. Eukaryotic: internal membranes / membrane bound organelles / presence of mitochondria / double nuclear membrane;
Ribosomes Ribosomes are microscopic spheres attached to the ER or freefloating in the cytoplasm Ribosomes are protein factories Larger subunit Ribosomes are made of several components: Two protein subunits & rrna Small subunit
Ribosomes Bound ribosomes: attached to the ER generally proteins synthesized by bound ribosomes are secreted by the cell Free ribosomes: suspended in cytosol generally proteins synthesized by free ribosomes remain in the cell
Cell Membrane Functions of cell membrane: protects cell from outside environment; keeps cell contents together; and selectively allows materials to cross into & out of cell.
Cell Membrane
Cell Membrane Phospholipid: composed of a phosphate head and fatty acid tails. Hydrophilic Head is water loving or soluble in water. Hydrophobic Tails are water hating or insoluble in water. Proteins: float around within the membrane or on its surface; functions include: structural support, surface binding sites for molecules like hormones, recognition sites for cell to cell communication & interaction, transport molecules across the membrane, transport electrons & protons within the membrane Glycocalyx: carbohydrate chains attached to proteins (glycoproteins), involved in recognition & communication proteins, points for cell to cell attachment Cholesterol: keeps the phospholipids stable and helps retain the membrane s shape
Chloroplasts Chloroplasts are found only in green plants They convert sunlight to chemical energy via photosynthesis: sunlight + CO 2 + H 2 O -> sugar + O 2 )
Chloroplast structures Stroma: chloroplast cytosol Lamella: membrane that attaches inner chloroplast structures Thylakoid disk: have a specialized membrane for photosynthesis Grana: stack of thylakoid discs Chloroplast DNA: self-replicating organelle
Vacuoles Vacuoles contain water and salts It exerts pressure from within, making the cell turgid and firm 27
Extracellular Components Outside of the cell is called Extracellular Matrix (ECM) Animal cells secrete glycoproteins to form the ECM Helps in support, adhesion and movement 28
Identify the following parts I Identify part I & II What type of cell is shown? How do you know? II I is Chloroplast II is nucleus Plant cell since they contain chloroplasts 29
Identify the following parts II III I Identify part I, II & III Is this cell eukaryotic or prokaryotic? I is Golgi apparatus II is Nuclear pore III is Nucleolus Eukaryotic 30
Identify the following parts I II Identify I & II What is the function of II? I is Rough ER II is Ribosomes Protein synthesis 31