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Basic Structure of a Cell
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Introduction to CellsIntroduction to CellsCells are the basic units of organismsCells can only be observed under microscope (history given in text)
Basic types of cells:
Animal Cell Plant Cell Bacterial Cell
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Cell TheoryCell Theory• All living things composed of 1 or more cells
• Cells basic unit of structure & function in an organism
• Cells come from other living cells
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Number of CellsOrganisms may be:• Unicellular –composed of one cell• Multicellular-composed of many cells that may organize
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Prokaryotes include bacteria & lack a nucleus or membrane-bound structures called organelles
Eukaryotes include most other cells & have a nucleus and membrane-bound organelles (plants, fungi, & animals)
Cells May be Prokaryotic or Eukaryotic
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ProkaryotesNucleoid region contains the DNA
•Cell membrane & cell wall
• Contain ribosomes(no membrane) to make proteins in their cytoplasm
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Eukaryotic CellContain 3 basic cell structures:
• Nucleus• Cell Membrane• Cytoplasm with organelles
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Two Main Types of Eukaryotic Cells
Plant Cell Animal Cell
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Cell Size & ShapeBasic cell size is limited by:
• Outer surface area• VolumeDetermined by a ratio
between them
Lab E1
Cell shape enables its to perform its function
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OrganellesOrganelles
Very small size
Can only be observed under a microscope
Have specific functions
Found throughout cytoplasm
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Organelles Found in CellsExamples of Organelles include:
Endoplasmic reticulum (rough & smooth) –canals for movement
Golgi Bodies – wrap & export proteins
Nucleolus – makes ribosomes
Lysosomes – digests & gets rid of wastes
Ribosomes – makes proteins
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Golgi Bodies•• Stacks of Stacks of flattened flattened
sacssacs•• Have a shipping side & Have a shipping side &
a receiving sidea receiving side•• Receive & Receive & modify modify
proteinsproteins made by ERmade by ER•• Transport vesiclesTransport vesicles
with modified proteins with modified proteins pinch off the endspinch off the ends Transport
vesicle
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Lysosome•• Contain digestive Contain digestive
enzymesenzymes•• Break down food and Break down food and
worn out cell parts for worn out cell parts for cells cells
•• Programmed for cell Programmed for cell death (death (lyselyse & release & release enzymes to break down enzymes to break down & recycle cell parts)& recycle cell parts)
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Nucleolus•• Cell may have Cell may have 1 to 31 to 3
nucleolinucleoli•• Inside nucleusInside nucleus•• DisappearsDisappears when cell when cell
dividesdivides•• Makes Makes ribosomesribosomes that that
make proteinsmake proteins
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Smooth & Rough Endoplasmic Reticulum
Smooth ER lacks ribosomes & makes proteins USED In the cell
Rough ER has ribosomes on its surface & makes proteins to EXPORT
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Rod shapeSite of Cellular respiration
Cell PowerhouseCell Powerhouse
Mitochondrion( mitochondria )
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Active cells like muscles have more mitochondriaBurn sugars to produce energy ATP
In Animal Cells:In Animal Cells:
Mitochondria
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Lies immediately against the cell wall in plant cells
Made of protein and phospholipids
Selectively permeable
Cell membrane
Surrounding the CellSurrounding the Cell
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Living layerControls the movement of materials into and out of the cell
Selectively permeable
Cell membrane
Cell or Plasma MembraneCell or Plasma Membrane
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Jelly-like substance enclosed by cell membrane
Provides a medium for chemical reactions to take place
Cytoplasm
Cytoplasm of a Cell Cytoplasm of a Cell
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Contains organelles to carry out specific jobs
Examples:chloroplast & mitochondrion
Cytoplasm
More on CytoplasmMore on Cytoplasm
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Controls the normal activities of the cell
Bounded by a nuclear membrane
Contains chromosomes
Control Organelle
Nucleus
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Each cell has fixed number of chromosomes that carry genes
Genes control cell characteristics
Nucleus
More on the NucleusMore on the Nucleus
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Contain the green pigment chlorophyll
Traps sunlight to make to make sugars (food)
Process called photosynthesis
Plant Cell OrganellesPlant Cell Organelles
Chloroplast
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Dead layerLarge empty spaces present between cellulose fibers
Freely permeable
Cell wall
Plant CellPlant Cell
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Plant CellPlant Cell
Made of cellulose which forms very thin fibers
Strong and rigidFound in plant cells
Cell wall
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Protect and support the enclosed substances (protoplasm)
Resist entry of excess water into the cell
Give shape to the cell
Cell wall
Plant CellPlant Cell
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Have a large central vacuole
Surrounded by tonoplastContains cell sapSugars, proteins,
minerals, wastes, & pigments
Plant Cell OrganellesPlant Cell OrganellesVacuole
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Different kinds of plant Different kinds of plant cellscells
Onion Epidermal Cells
Root Hair Cell
root hair
Guard Cells
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mitochondrion
nucleus
glycogen granule
cell membrane
cytoplasm Animal cellAnimal cell
No cell wall or chloroplastStores glycogen in the cytoplasm for food energy
vacuole
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Animal Cell OrganellesAnimal Cell Organelles
• Near the nucleus• Paired structures• Help cell divide
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Different kinds of animal Different kinds of animal cellscells
white blood cell
red blood cell
cheek cellssperm
nerve cell
muscle cell
Amoeba
Paramecium
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Similarities between plant Similarities between plant cells and animal cellscells and animal cells
Both have a cell membrane surrounding the cytoplasm
Both have a nucleus
Both contain mitochondria
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Differences between plant Differences between plant cells and animal cellscells and animal cells
Animal cells Plant cells
Relatively smaller in sizeIrregular shape
No cell wall
Relatively larger in sizeRegular shape
Cell wall present
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Animal cells Plant cells
Vacuole small or absent
Glycogen as food storage
Nucleus at the center
Large central vacuole
Starch as food storage
Nucleus near cell wall
Differences between Plant Differences between Plant Cells and Animal CellsCells and Animal Cells
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Compound MicroscopeCompound Microscope
• Instrument for observing small objects
• Magnify images up to 2000X their size
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Different parts of Different parts of a microscopea microscope
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Eyepiece
Fine adjustment
Arm
Stage
Condenser control knob
Base
Body tubeCoarse adjustment
Iris diaphragm
Revolving nosepiece
Objective
Clip
Condenser
Mirror
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The cell is the Basic Unit The cell is the Basic Unit of Lifeof Life
• Cell is the smallest unit of living organisms• Unicellular organisms are made of one cell
only• The cells of multicellular organisms are
specialized to perform different functions– e.g. mesophyll cells for photosynthesis and root hair cells for water absorption
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Levels of organizationLevels of organization• Cells are grouped together and work as a whole to perform special functions
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TissueTissue• A group of similar cells to perform a particular function– Animals : epithelial tissue, muscular tissue
– Plants : vascular tissue, mesophyll
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OrganOrgan• Different tissues group together to carry out specialized functions– Heart : consists of muscles, nervous tissue and blood vessels
– Leaf : consists of epidermis, mesophyll and vascular tissue
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Stoma
Air Space
Spongy Mesophyll Cell
Chloroplast
The Structures of a Leaf (Plant Organ)
Palisade Mesophyll Cell
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The Structures of a Heart (Animal Organ)
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SystemSystem• Several organs and tissues work together
to carry out a particular set of functions in a co-ordinated way– Human : digestive, respiratory, excretory, circulatory and reproductive systems
– Plant : root and shoot systems
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Human Body SystemsHuman Body SystemsExamples of systems :
Digestive SystemRespiratory SystemCirculatory SystemNervous SystemReproductive System
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Examples of a Human Body System
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Examples of a Human Body SystemThe Respiratory System
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Examples of a Human Body SystemCirculatory System
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Examples of a Human Body SystemNervous System
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Levels of OrganizationLevels of Organization
CELLS (muscle cells,nerve cells)TISSUES (muscle, epithelium)ORGANS (heart, lungs, stomach)SYSTEMS (circulatory system)ORGANISM (human)