all organisms are composed of one or more cells. cells are
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All organisms are composed of one or more cells.
Cells are the smallest living units of all living organisms.
Cells arise only by division of a previously existing cell.
Amoeba Proteus
Plant Stem
Red Blood Cell
Nerve Cell
Bacteria
Genetic material single circular molecule of DNA in prokaryotes
double helix located in nucleus in eukaryotes – nuclear envelope (double membrane
Cytoplasm fills cell interior – sugars, amino acids,
proteins - organelles
Plasma membrane encloses the cell – phospholipid bilayer
Phospholipid
Membrane proteins
Most cells are relatively small because as size increases, volume increases much more rapidly.
longer diffusion time
1. Ion Channels – specific for Na+, K+, CA+2, Cl+
- can open or close
2. Transporter (Carrier) Proteins – specific for sugar, amino acids
- may require energy (ATP) “Active Transport”
3. Enzymes – catalyze specific reactions
4. Receptor Sites – located on the outer surface of the cell membrane
- specific for certain hormones, neurotransmitters, drugs
- activation of receptor site = changes in cell activity
Specific solutes (chemicals) bind to specific protein carriers which channel them through membranes by carrier-mediated transport.
The transport may be active, requiring metabolic energy (as from ATP), or passive, requiring no metabolic energy.
The transport of amino acids requires ATP but the transport of sugars does not require ATP
5. Recognition Sites – glycoproteins located on the outer surface of the cell membrane
- allow WBC’s to “recognize” your cells from foreign antigens
Resolution - minimum distance two points can be apart and still be distinguished as two separate points
Compound microscopes - magnify in stages using multiple lenses
Transmission electron microscope - electrons transmitted through specimen
Scanning electron microscope - electrons beamed onto surface of the specimen
Simplest organisms
Cytoplasm is surrounded by plasma membrane and encased in a rigid cell wall composed of peptidoglycan.
no distinct interior compartments
gram-positive – thick single layer wall that retains a violet dye from Gram stain procedure
gram-negative – multilayered wall does not retain dye
Susceptibility of bacteria to antibiotics depends on cell wall structure.
Some use flagellum for locomotion
threadlike structures protruding from cell surface
Bacterial cell wall
Flagellin
Rotary motor
Sheath
Characterized by compartmentalization by an endomembrane system, and the presence of membrane-bound organelles.
Central vacuole – plants, storage
Vesicles (smaller)
Chromosomes - DNA and protein
Cytoskeleton (internal protein scaffolding)
Cell walls – plants and fungi
Repository for genetic material
Directs activities of the cell
Usually single, some cells several, RBC none Nucleolus - region of intensive ribosomal RNA synthesis
Surface of nucleus bound by two phospholipid bilayer membranes nuclear membrane
Nuclear pores – protein gatekeepers Usually proteins going in and RNA going out
DNA of eukaryotes is divided into linear chromosomes.
exist as strands of chromatin, except during cell division
associated with packaging histones, packaging proteins
nucleosomes
Compartmentalizes cell, channeling passage of molecules through cell’s interior.
Endoplasmic reticulum
Rough ER - studded with ribosomes
Smooth ER - few ribosomes
Largest internal membrane
Composed of Lipid bilayer
Serves as system of channels from the nucleus
Functions in storage and secretion
Rough ER is “rough” because of associated ribosomes (sites of protein synthesis)
Smooth ER - lack associated ribosomes – contains embedded enzymes, catalyze synthesis of carbohydrate and lipid molecules
Golgi apparatus
collection of Golgi bodies
collect, package, and distribute molecules synthesized at one location in the cell and utilized at another location
Front - cis , Back – trans
Cisternae – stacked membrane folds
Vesicle budding from rough endoplasmic reticulum
Fusion of vesicle with Golgi apparatus
Migrating transport vesicle
Protein
Proteins
Transport vesicle
Golgi apparatus
Cisternae
Ribosome
trans face
cis face
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Vesicles Lysosomes - membrane-bound vesicles containing
digestive enzymes – from Golgi
Microbodies - enzyme-bearing, membrane-enclosed vesicles. Peroxisomes - contain enzymes that catalyze the removal
of electrons and associated hydrogen atoms
Peroxisome – named for hydrogen peroxide produced as a by-product
Enzyme breaks down to water and oxygen
Cytoplasm
Phagocytosis
Food vesicle
Golgi apparatus
Lysosomes
Plasma membrane
Digestion of phagocytized food particles
or cells
Endoplasmic reticulum
Transport vesicle
Old or damaged organelle
Breakdown of old
organelle Extracellular fluid
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Ribosomes are RNA-protein complexes composed of two subunits that join and attach to messenger RNA.
site of protein synthesis
assembled in nucleoli
In 1965 Robert Hooke observed slices of cork from the bark of a tree under a simple magnifying glass. He noticed small boxes or compartments in the cork slice. The boxes were separated from each other by a wall or partition. He named each box as a Cell. The cells which Hooke observed were actually dead cells of plants.
Mitochondria
bounded by exterior and interior membranes
interior partitioned by cristae
Chloroplasts
have enclosed internal compartments of stacked grana, containing thylakoids
found in photosynthetic organisms
A. "Powerhouse of the cell" - cellular
metabolism
B. Structure- outer and inner membranes,
cristae
C. Have their own DNA
•Chloroplasts are larger and more complex than
mitochondria
•Grana – closed compartments of stacked membranes
•Thylakoids – disc shaped structure – light capturing
pigment
•Stroma – fluid matrix
Network of protein fibers supporting cell shape and anchoring organelles Actin filaments
cell movement Microtubules
Hollow tubes Facilitate cell movement Centrioles – barrel shaped organelles occur in pairs – help assemble animal cell’s microtubules
Intermediate filaments Stable - don’t break down
Actin
Microtubules
Intermediate
filaments
Central vacuole often found in the center of a plant, and serves as a
storage facility for water and other materials
Cell wall primary walls – laid down while cell is growing
middle lamella – glues cells together
secondary walls – inside the primary cell walls after growth
Animal cells lack cell walls.
form extracellular matrix
provides support, strength, and resilience
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