Basic Structure of a Cell
Prokaryotic Cells No nucleus Archaea & Eubacteria One circular chromosome Extremely small Eukaryotic Cells Has a nucleus!!! Membrane-bound organelles Plants, Animals, Fungi, & Protists
Prokaryotes The first Cells Cells that lack a nucleus or membrane-bound organelles Includes bacteria Simplest type of cell Single, circular chromosome
Nucleoid region (center) contains the DNA Surrounded by cell membrane & cell wall (peptidoglycan) Contain ribosomes (no membrane) in their cytoplasm to make proteins Prokaryotes
Prokaryotes Bacterial cells may have plasmids, small accessory rings of DNA. Some bacteria have a capsule or a slime layer. Most bacteria have flagella. Some also have fimbriae that help cells attach to surfaces. Bacteria have a great metabolic diversity.
Comparison of Eukaryotic and Prokaryotic Cells
Eu-, true, karyon, nucleus Genetic material contained in a nucleus Membrane-bound organelles Evolved from prokaryotic cells Includes protists, fungi, plants, and animals Eukaryotes
Eukaryotic No cell wall Heterotrophic Often highly specialized in multi-cellular organisms May be motile
DNA Nucleolus Nuclear envelope Centrosome Golgi complex Mitochondrion Lysosome Plasma membrane CELL WALL Wall of adjacent cell Rough ER Smooth ER Ribosomes CENTRAL VACUOLE Microfilaments Intermediate filaments Microtubules CHLOROPLAST Cell wall Outer layer that maintains cell s shape & rigidity and protects cell from mechanical damage Made primarily of cellulose Central vacuole Stores nutrients & breaks down waste products Contributes significantly to plant growth Chloroplast Contains chlorophyll, which is the primary pigment responsible for photosynthesis
Organelles Very small (Microscopic) Perform various functions for a cell Found in the cytoplasm May or may not be membrane-bound
Cell Wall Cell wall Nonliving layer that supports and protects the cell Found in plants, fungi, & bacteria Made of cellulose in plants Made of peptidoglycan in bacteria Made of chitin in Fungi
Cell Membrane in Plants Lies immediately against the cell wall in plant cells Cell membrane Pushes out against the cell wall to maintain cell shape
Cytoplasm of a Cell cytoplasm Jelly-like substance enclosed by cell membrane Provides a medium for chemical reactions to take place
More on Cytoplasm cytoplasm Contains organelles to carry out specific jobs Found in ALL cells
The Control Organelle - Nucleus Controls the normal activities of the cell Contains the DNA in chromosomes Bounded by a nuclear envelope (membrane) with pores Usually the largest organelle
More on the Nucleus Nucleus Chromosomes: Tightly coiled DNA & Protein Contain hereditary material (genes) Chromosomes not dividing called chromatin Each type of organism has a certain # of them Humans = 46 (23 pairs) Fruit fly = 8 (4 pairs)
Inside the Nucleus - The genetic material (DNA) is found DNA is spread out And appears as CHROMATIN in non-dividing cells DNA is condensed & wrapped around proteins forming as CHROMOSOMES in dividing cells
What Does DNA do? DNA is the hereditary material of the cell Genes that make up the DNA molecule code for different proteins
Nuclear Envelope Double membrane surrounding nucleus Also called nuclear membrane Contains nuclear pores for materials to enter & leave nucleus Connected to the rough ER Nuclear pores
Nucleolus Inside nucleus Cell may have 1 to 3 nucleoli Disappears when cell divides Makes ribosomes that make proteins
Endomembrane System System of transport throughout the cell Nuclear envelope Endoplasmic reticulum Golgi apparatus Lysosomes Vacuoles
Endomembrane System Includes nuclear membrane connected to ER connected to cell membrane (transport)
Endoplasmic Reticulum - ER Network of hollow membrane tubules throughout the cytoplasm Connects to nuclear envelope & cell membrane Functions: Transports materials through the cell Contains enzymes that allow chemical reactions Wastes & other toxic chemicals are made harmless Two types: Smooth ER Rough ER
The endoplasmic reticulum Rough ER: Studded with ribosomes Makes membrane proteins and proteins for export out of the cell Smooth ER: Lacks ribosomes on its surface Is attached to the ends of rough ER Makes cell products that are used inside the cell Site of synthesis of lipids (including phospholipids and steroids) Destroys toxic substances
Ribosomes Made of PROTEINS and rrna Made in the nucleolus Found mostly on ER but also floating in cytoplasm Found in all types of cells Protein factories for cell Join amino acids to make proteins (process called protein synthesis)
Golgi Complex (or Apparatus) Flattened membrane sacs Present in almost all cells Receives protein and lipid-filled vesicles from ER Modifies, sorts, and packages molecules from ER for storage or transport out of the cell
Vacuoles and Lysosomes Vacuoles (large) and vesicles (small) are membranous sacs in the cell that store substances. Lysosomes are vesicles produced by the Golgi apparatus. Lysosomes contain hydrolytic enzymes and are involved in intracellular digestion.
Vacuoles Fluid filled sacks for storage Small or absent in animal cells Plant cells have a large Central Vacuole In plants, they store Cell Sap Includes storage of sugars, proteins, minerals, lipids, wastes, salts, water, and enzymes No vacuoles in bacterial cells Many protists have contractile vacuoles
Contractile Vacuole Found in unicellular protists like paramecia Regulate water intake by pumping out excess (homeostasis) Keeps the cell from lysing (bursting)
Lysosomes Contain digestive enzymes Break down food, bacteria, and worn out cell parts for cells Some cells (i.e. certain types of protists) take in food by phagocytosis Lysosomes digest the food and get rid of wastes
Energy-Related Organelles The two energyrelated organelles of eukaryotes are mitochondria and chloroplasts. Both organelles house energy in the form of ATP.
Mitochondrion (plural = mitochondria) Found in all eukaryotic cells Powerhouse of the cell Site of Cellular Respiration: generate cellular energy (ATP) by burning glucose More active cells like muscle cells have MORE mitochondria
Structure: Mitochondrion (plural = mitochondria) Surrounded by a DOUBLE membrane Folded inner membrane called cristae (increases surface area for more chemical reactions) Interior called matrix Has its own DNA
Interesting Fact --- Mitochondria Come from cytoplasm in the EGG cell during fertilization Therefore You inherit your mitochondria from your mother!
Chloroplasts Organelle found only in producers Never in animal, fungal, or bacterial cells Contains enzymes & pigments for Photosynthesis Photosynthesis: Use energy from sunlight to make food (glucose) Energy from sun stored in the Chemical Bonds of Sugars Contains its own DNA
Chloroplasts Structure: Surrounded by DOUBLE membrane Outer membrane smooth Inner membrane modified into sacs called Thylakoids Thylakoids contain Chlorophyll a green pigment which absorbs energy from the sun Thylakoids are organized into stacks called Grana and are interconnected Stroma gel like material surrounding thylakoids
Process that uses solar energy to convert carbon dioxide and water into glucose and oxygen Structure of Chloroplast: Surrounded by double membrane Outer membrane is smooth Inner membrane is modified into sacs called Thylakoid Discs Thylakoid membranes contain Chlorophyll Thylakoids are organized into stacks called Grana and are interconnected Stroma gel like material surrounding thylakoids Outer membrane Inner membrane Stroma Granum Thylakoid discs
Cytoskeleton Network of filaments and tubules that extends from the nucleus to the plasma membrane Made of proteins Helps cell maintain cell shape Also help move organelles around Types: Microfilaments threadlike and made of Actin Microtubules tubelike and made of Tubulin Intermediate filaments MICROTUBULES MICROFILAMENTS
Centrioles Found only in animal cells Paired structures near nucleus Made of bundle of microtubules Appear during cell division forming mitotic spindle Help to pull chromosome pairs apart to opposite ends of the cell
Made of protein tubes called microtubules Cilia & Flagella Microtubules arranged (9 + 2 arrangement) Function in moving cells, in moving fluids, or in small particles across the cell surface
Cilia are shorter and more numerous on cells Cilia & Flagella Flagella are longer and fewer (usually 1-3) on cells
Cell Movement with Cilia & Flagella