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THE CELL - PowerPoint PPT Presentation


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THE CELL. Cell Structure and Communication. Cell Size. 1. Higher plant cells, 10-100 µ m long 2. Bacterial cells, 0.5-1.0 µ m long 3. Pear tree leaf contains ~ 50 million cells 4. Full grown pear tree contains ~ 15 trillion cells. The Cell Wall. 1. Found outside plasma membrane

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cell size
Cell Size
  • 1. Higher plant cells, 10-100 µm long
  • 2. Bacterial cells, 0.5-1.0 µmlong
  • 3. Pear tree leaf contains ~ 50 million cells
  • 4. Full grown pear tree contains ~ 15 trillion cells
the cell wall
The Cell Wall
  • 1. Found outside plasma membrane
  • 2. Consists of mostly cellulose
    • cellulose molecules grouped into bundles known as microfibrils
  • 3. Pectins form the middle lamella
  • 4. First formed walls called primary walls, then secondary walls may be formed
  • 5. Lignin may be part of cell wall giving mechanical strength to wall
  • 6. Plasmodesmata interconnect living plant cells
communication between cells
Communication Between Cells
  • 1. Plasmodesmata
    • fine strands of cytoplasm interconnect plant cells
the plasma membrane
The Plasma Membrane
  • 1. Outer boundary of living cell, extremely thin
  • 2. Mosaic structure composed of phospholipids and proteins
  • 3. Unit membrane structure seen with electron microscope
the nucleus
The Nucleus
  • 1. Most conspicuous organelle, generally spherical or ellipsoidal in shape
  • 2. Control center of the cell, stores hereditary information
  • 3. DNA in nucleus makes a copy of itself (RNA) as a blueprint for directing proteinsythesis
  • 4. Contains 2 membranes (outer and inner), called the nuclear envelope, which contains pores to allow passage of certain molecules
  • 5. Outer membrane connected to endoplasmic reticulum
  • 6. Nucleoplasm is the granular-appearing fluid inside the nuclear envelope
  • 7. Nucleoli are larger bodies noticeable in the nucleoplasm
  • • involved in RNA synthesis
  • 8. Chromatin is the thread-like DNA strands which shorten and condense intochromosomes when the cell is ready to divide
  • • chromatin composed of DNA and protein
the endoplasmic ret iculum
The Endoplasmic Reticulum
  • 1. Complex system of membrane channels
  • 2. Outer surface of membranes may be covered with ribosomes
  • 3. Called “rough” ER because of pebbly appearance
  • 4. “Smooth” ER has no ribosomes
  • 5. Protein synthesis, secretion and storage associated with rough ER
ribosomes
Ribosomes
  • 1. Occur free in cytoplasm, mitochondria and chloroplast, or associated with rough ER
  • 2.Roughly ellipsoidal in shape, approximately 17-25 nm in diameter
  • 3.Function in protein synthesis by linking amino acids together
  • 4. Ribosome composed of two subunits, made up of RNA and proteins
dictyosomes
Dictyosomes
  • 1. Groups of flat, roundish sacs, organized into stacks
  • 2. Collecting and packaging centers for proteins and other molecules like carbohydrates
  • 3. Golgi complex is continuous with endoplasmic reticulum canals on one side and to secretary vesicles leading the cell membrane on the other.
plastids three types
Plastids Three Types
  • 1. Chloroplasts
  • 2. Chromoplasts
  • 3. Leucoplasts
plastids
Plastids
  • 1. Three Types
  • a. Chloroplasts
  • 1) Most common type, green in color
  • 2) Stroma, enzyme containing region
  • 3) Grana membranes called thylakoids, suspended in the stroma
plastids type cont
Plastids type cont
  • b. Chromoplasts
  • 1) Contain colored pigments such as carotenoids
  • 2) Give orange, red, and yellow colors to various plant parts
  • c. Leucoplasts
  • 1) Colorless
  • 2) Types
  • i) Amyloplasts, store starch granules
  • ii) Elaioplasts, store oils
plastids type cont1
Plastids type cont
  • 2. Proplastids
  • • all plastids develop from these
mitochondria
Mitochondria
  • 1. “Power-houses” of the cell
  • 2. Function in generation of ATP, the energy molecule of the cell
  • 3. Small organelles, 1-3 µm in length, look like tiny membranes
  • 4. Outer and inner membranes present
  • • inner membrane has inward extensions or folds called cristae
microbodies
Microbodies
  • 1. Small spherical organelles, bounded by a single membrane
  • 2. Contain enzymes which function in photosynthesis, photorespiration, and conversion of fats to carbohydrates
  • 3. Lysosomes
  • a. Store digestive enzymes (more typical of animal cells)
  • b. Digestive activities similar to vacuoles of plant cells
  • 4. Microbodies seen only with an electron microscope
vacuoles
Vacuoles
  • 1. Membrane bound sacs filled with a watery fluid called cell sap
  • • vacuolar membrane called the tonoplast
  • 2. Cell sap contains salts, sugars, organic acids, and may contain water-soluble pigments
  • called anthocyanins(red blue in color)
  • 3. Vacuoles are small and numerous in size in newly formed cells but increase in size as cell

matures

the cytoskeleton
The Cytoskeleton
  • 1. Microtubules
  • a. Unbranched, thin, hollow tube-like structures
  • b. Composed of protein
  • c. 15-25 nm in diameter and of various lengths
  • d. Found inside plasma membrane, help control the addition of cellulose to the cell wall
  • e. Other functions, vesicle transport, motility of flagella and cilia, and component of mitotic

spindle

the cytoskeleton cont
The Cytoskeleton cont.
  • 2. Microfilaments
  • a. Long protein filaments approximately 6 nm in diameter
  • b. Often grouped together in bundles
  • c. Function in cytoplasmic streaming and as part of the framework of the cell
the cytoskeleton cont1
The Cytoskeleton cont.
  • 3. Cyclosis
  • a. cytoplasmicstreaming exhibited by all living cells
  • b. Function
  • • facilitates exchange and movement of materials within a cell
  • c. Movement
  • • microfilaments and microtubules are thought to be responsible for generating the movement of the

cytoplasm

a unique structures of plant cells
A. Unique Structures of Plant Cells
  • 1. Cell walls
  • 2. Plasmodesmata
  • 3. Cell plate
b minor differences
B. Minor Differences
  • 1. Plant cells lack centrioles
  • • animal cells have these
  • 2. Plant cells contain plastids
  • • animal cells have none
  • 3. Vacuoles, common in plant cells
  • • either small or absent in animal cells