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Chapter 7. Cell Structure and Function
Biology
7.1 Life is CellularThe Discovery of the Cell
1665, Robert Hooke used a microscope to look at a thin slice of cork.
Look like tiny, empty chambers.
Hooke named the chambers “cells”
Anton van Leeuwenhoek observed pond water, revealed tiny living organisms.
7.1 Life is CellularThe Cell Theory
Cells are the basic unit of life.
1838, Matthias Schleiden concluded all plants are made up of cells.
1839, Theodor Schwann stated that all animals were made up of cells
1855, Rudolf Virchow concluded that new cells could be produced only from the division of existing cells.
7.1 Life is CellularThe Cell Theory
These discoveries are summarized in the cell theory:
1. All living things are composed of cells.
2. Cells are the basic unit of structure and function in living things.
3. New cells are produced from existing cells.
7.1 Life is CellularExploring the Cell
Fluorescent labels and light microscopy
Confocal light microscopy High-resolution video
technology Scanning Electron
Microscope Transmission Electron
Microscope Scanning Probe
Microscopes
Let’s look at page 170…
7.1 Life is CellularProkaryotes and Eukaryotes
Cells are very diverse Size ranges from 5 to 50
micrometers in diameter Tiniest – mycoplasm, 0.2
micrometers Larger – Chaos chaos
(Giant Amoeba), 1000 micrometers
All are surrounded by a barrier called a cell membrane and contain DNA.
7.1 Life is CellularProkaryotes and Eukaryotes
Two categories depending on the presence of a nucleus
Nucleus – a large membrane-enclosed structure that contains the cell’s genetic material in the form of DNA
Eukaryotes – cells that contain nuclei.
Prokaryotes – cells that do not contain nuclei.
Prokaryotic Cell
Cell membrane
Cell membrane
Cytoplasm
Cytoplasm
Nucleus
Organelles
Eukaryotic Cell
7.1 Life is CellularProkaryotes
Smaller and simpler than eukaryotic cells.
Genetic material is not contained in the nucleus.
Carry out every activity associated with living things.
Ex. Bacteria
Can you name this bacteria?
7.1 Life is CellularEukaryotes
Larger and more complex than prokaryotic cells.
Contain dozens of structures and internal membranes.
Contain a nucleus in which their genetic information is separated from the rest of the cell.
Can be single celled, or multicellular.
Ex. Plants, animals, fungi, and protists.
Venn Diagram
http://live.bcps.org/web_flash/arcade/2011/prokaryotes_vs_eukaryotes.swf
SECTION 2- ORGANELLES
7.2 Eukaryotic Cell StructureComparing the Cell to a Factory
Eukaryotic cells have structures that can be compared to specialized organs called organelles, “little organs.”
Two major parts: the nucleus and the cytoplasm.
Cytoplasm – portion of the cell outside the nucleus.
7.2 Eukaryotic Cell StructureNucleus
Nuclear envelope – surrounds the nucleus, contains thousands of nuclear pores.
Chromatin – DNA bound to protein (condenses when a cell divides to form chromosomes).
Chromosomes – contain genetic information that is passed from one generation of cells to the next.
Nucleolus – small, dense region where the assembly of ribosomes begin.
The nucleus contains nearly all the cell’sDNA and with it the coded instructionsfor making protein and other importantmolecules.
7.2 Eukaryotic Cell StructureRibosomes
Proteins are assembled on ribosomes.
Produce proteins by following coded instruction that come from the nucleus.
Cell that are active in protein synthesis are often packed with ribosomes.
Can be free or fixed
7.2 Eukaryotic Cell StructureEndoplasmic Reticulum
Endoplasmic reticulum – the site where lipid components of the cell membrane are assembled, along with proteins and other materials that are exported from the cell.
Rough Endoplasmic Reticulum (RER) – synthesis of proteins where they can be modified
Smooth Endoplasmic Reticulum (SER) – synthesis of membrane lipids and the detoxification of drugs
7.2 Eukaryotic Cell StructureGolgi Apparatus
The function of the Golgi Apparatus is to modify, sort, and package proteins and other materials from the endoplasmic reticulum for the storage in the cell or secretion outside the cell.
Comparison – put on the finishing touches and then “shipped.” **Jeopardy Fact: Discovered by Camillo Golgi
7.2 Eukaryotic Cell StructureLysosomes
“Clean up crew” Small organelles filled
with enzymes that digest lipids, carbohydrates, and proteins that can be used by the rest of the cell.
Also, remove “old” organelles
7.2 Eukaryotic Cell StructureVacuoles
Vacuoles – saclike structure that store “things.”
Store water, salts, proteins, and carbohydrates
Ex. Central vacuole (plant) and contractile vacuole (paramecium)
7.2 Eukaryotic Cell StructureMitochondria
All living things need a source of energy.
Mitochondria are organelles that convert chemical energy stored in food into compounds that are more convenient for the cell to use.
“power house of the cell” Mitochondria have two
membranes Inherited from the female
7.2 Eukaryotic Cell StructureChloroplasts
Chloroplasts – organelles that capture the energy from sunlight and convert it into chemical energy in a process called photosynthesis.
“Solar power plants” Also contain a double
membrane. Green pigment -
chlorophyll
7.2 Eukaryotic Cell StructureOrganelle DNA
Mitochondria and chloroplast have their own DNA
Theory – descendants of ancient prokaryotes (developed a symbiotic relationship)
Predation, Competition, Symbiosis, Mutalism, Commensalism, Parasitism
7.2 Eukaryotic Cell StructureCytoskeleton
Cytoskeleton – network of protein filaments that helps the cell to maintain its shape. The cytoskeleton is involved in movement.
Microfilaments – threadlike, made up of actin, helps cell move
Microtubules – hollow, made up of tubulin, maintain cell shape, separate chromosomes during cell division (centrioles), help build flagella and cilia
Cell membrane
Endoplasmicreticulum
Microtubule
Microfilament
Ribosomes Mitochondrion
7.2 Eukaryotic Cell StructureAnimal Cell
Centrioles
NucleolusNucleus
Nuclearenvelope
Rough endoplasmic reticulum
Golgi apparatus
Smooth endoplasmicreticulum
Mitochondrian
CellMembrane
Ribosome(free)
Ribosome(attached)
7.2 Eukaryotic Cell StructurePlant Cell
Nuclearenvelope
Ribosome(attached)
Ribosome(free)
Smooth endoplasmicreticulum
Nucleus
Rough endoplasmic reticulum
Nucleolus
Golgi apparatus
Mitochondrian
Cell wall
CellMembrane
Chloroplast
Vacuole
7.3 Cell BoundariesCell Membrane
The cell membrane regulates what enters and leaves the cell and also provides protection and support
Called a “phospholipid bilayer.”
Also contains proteins (channels and pumps) and carbohydrates (identification), referred to as a mosaic
7.3 Cell BoundariesCell Membrane
Cellmembrane
Proteins
Proteinchannel Lipid bilayer
Carbohydratechains
7.3 Cell BoundariesCell Wall
Present in many organisms, including plants, algae, and many prokaryotes
Allows water, oxygen, and carbon dioxide to pass through
Main Function: provide support and protection
Composed of mostly cellulose.
7.3 Cell BoundariesDiffusion Through Cell Boundries
One of the most important functions of the cell membrane is to regulate movement of dissolved molecules from the liquid side of the membrane to the liquid on the other side
Measuring Concentration Concentration – the mass of
solute in a given volume of solution, or mass/volume
7.3 Cell BoundariesDiffusion
Diffusion – movement from an area of more concentration to an area of less concentration
Equilibrium – when the concentration of the solute is the same throughout the system
Why do we care? This occurs on both sides of
the cell membrane. Does NOT require energy Particles are constantly
moving
http://www.indiana.edu/~phys215/lecture/lecnotes/lecgraphics/diffusion2.gif
7.3 Cell BoundariesOsmosis
Some substances cannot pass through the cell membrane – impermeable
Most biological membranes are selectively permeable.
Water is permeable to most membranes.
Osmosis – the diffusion of water through a selectively permeable membrane.
7.3 Cell BoundariesOsmosis
Higher Concentrationof Water
Lower Concentrationof Water
Cellmembrane
Water molecules
Sugar molecules
7.3 Cell BoundariesHow Osmosis works
Movement of water from an area of high concentration to the area of low concentration – until equilibrium is met
Isotonic – “same strength”
Hypertonic – “above strength”
Hypotonic – “below strength”
7.3 Cell BoundariesOsmotic Pressure
Osmotic pressure can cause serious problems for a cell.
Cells are bathed in fluids, such as blood that are isotonic, to prevent this
Plant and bacteria cells are surrounded by tough cell walls, to prevent expansion
7.3 Cell BoundariesFacilitated Diffusion
Cell membranes have protein channels that make it easy for certain molecules to cross the membrane
The cell protein is said to facilitate, or help, the molecule. This is called facilitated diffusion.
Fast and specific Will only in occur with a
concentration gradient Does NOT need energy
HighConcentration
CellMembrane
LowConcentration
Proteinchannel
Glucosemolecules
7.3 Cell BoundariesActive Transport
Sometimes, molecules need to be moved against the concentration gradient
This is called active transport, because it requires energy.
Carried out by protein channels or “pumps.”
LowConcentration
CellMembrane
HighConcentration
Moleculebeing carried
LowConcentration
CellMembrane
HighConcentration
7.3 Cell BoundariesMolecular Transport
Many cells use proteins to move calcium, potassium, and sodium ions across cell membranes
A considerable amount of energy is used by cells to keep active transport working
7.3 Cell BoundariesEndocytosis and Exocytosis
Endocytosis – the process of taking material into the cell by means of enfolding's, or pockets, of the cell membrane– Pinocytosis – process by which
a cell takes in liquid from the surrounding environment
– Phagocytosis – process by which extensions of cytoplasm surround and engulf large particles and take them into the cell
Exocytosis – the membrane of the vacuole surrounding the material fuses with the cell membrane, forcing the contents out of the cell
7.4The Diversity of Cellular LifeUnicellular Organisms
A single celled organism is also called a unicellular organism
They grow, respond to the environment, transform energy, and reproduce
They dominate this Earth!
Leptospira interrogans
7.4The Diversity of Cellular LifeMulticellular Organisms
Organisms that are made up of many cells are called multicellular.
Cells throughout an organism can develop in different ways to perform different tasks, this is called cell specialization.
7.4The Diversity of Cellular LifeSpecialized Animal Cells
Ex. Red blood cells carry oxygen, pancreatic cells produce proteins for digestion, muscle cells to help us move
Can you identify these specializedAnimal cells???
7.4The Diversity of Cellular LifeSpecialized Plant Cells
Ex. Guard cells monitor the plants internal conditions, communicates with the stomata
What’s going on here???
7.4The Diversity of Cellular LifeLevels of Organization
The levels of organization in a multicellular organism are individual cells, tissues, organs, and organ systems.
Muscle cell Smooth muscle tissue Stomach Digestive system
7.4The Diversity of Cellular LifeTissues
Tissue – group of similar cells that perform a particular funtion.
Ex. Pancreatic tissues that make enzymes
Animal tissue: muscle, epithelial, nervous, and connective
Do you know what type of tissue this is?
7.4The Diversity of Cellular LifeOrgans
Organ – many tissues working together
Ex. Within a muscle there is more than one type of tissue…nerve, connective, etc.
Jeopardy question…What is OURLargest organ???
7.4The Diversity of Cellular LifeOrgan Systems
Organ system – a group of organs that work together to perform a specific function.
We rely on Interdependence