The Cell Flashcards
The cell theory can be summarized as
All living things are composed of cells.
The cell is the basic functional unit of life.
Cells arise only from pre-existing cells.
Cells carry genetic information in the form of DNA which is passed from parent to daughter cell.
The three primary methods available to study the cell and it’s structures are
Microscopy, autoradiography and centrifugation
The compound light microscope is used in
The observation of non-living specimens.
Contrast is obtained through staining techniques.
Total magnification is equal to the product of the eyepiece magnification and the magnification of the selected objective lense.
Phase contrast microscope
Used to study living specimens.
Differences in refractive index are used to produce contrast between cellular structures.
Electron microscope
Uses a beam of electrons to allow 1000x higher magnification then possible with light microscopy.
Tissues must be fixed and sectioned and sometimes stained with solutions of heavy metals.
Autoradiography
Uses radioactive molecules to trace and identify cell structures and biochemical activity ( such as protein synthesis)
Centrifugation
Can be used to separate cells or mixtures of cells with out destroying them.
At low speeds cell mixtures separate based on cell type.
At high speeds cell components separate based on their densities.
Example: ribosomes on bottom and mitochondria and lysosomes on top.
Prokaryotes
Bacteria and cyanobacteria. Contain cell wall. No nucleus. Ribosomes ( subunits = 30s and 50s) No membrane bound organelles.
Eukaryotes
Protist, fungi, plants and animals.
Cell wall present in fungi and plants only.
Contain a nucleus with DNA organized into chromosomes.
Ribosomes ( subunits = 40s and 60s)
Membrane bound organelles suspended in semi-fluid medium called cytosol.c
Cell membrane
Composed of phospholipid bilayer. Exhibits selective permeability. Smaller non-polar ( hydrophobic) molecules defuse freely. Charged ions ( hydrophilic) and large molecules may requires a carrier protein.
Nucleus
Surrounded by nuclear membrane or envelope.
Nuclear pores allow 2 way exchange of materials between nucleus and cytoplasm.
Contains DNA complexed with his tones to form chromosomes.
Nucleolus
Dense structure in nucleus where ribosomal RNA (rRNA) synthesis occurs.
Ribosomes
Site of protein production.
Synthesized by the nucleolus.
Consists of two subunits.
Each subunit composed of rRNA and proteins.
Free ribosomes - found in cytoplasm
Bound ribosomes - line outer membrane of endoplasmic reticulum
Endoplasmic reticulum
network of membrane enclosed spaces connected at points with the nuclear membrane.
With ribosomes - rough ER
Without ribosomes - smooth ER
Endoplasmic reticulum is involved in
Transport of materials through the cell.
Smooth ER- involved in lipid synthesis and detoxification of drugs and poisons.
Rough ER- involved in protein synthesis
Bound ribosome synthesize proteins which then
cross into cisternae of RER and undergo chemical modification.
Then cross into smooth ER, secreted into cytoplasmic vesicles and transported to Golgi apparatus
Golgi apparatus
Stack of membrane enclosed sacs.
Receives vesicles from smooth ER, modifies them (eg glycosylation) repackages into vesicles and distributes.
Secretory vesicles produced by Golgi release contents into cells exterior via exocytosis.
Vesicles and vacuoles
Membrane-bound sacs involved in transport and storage.
Vacuoles are larger than vesicles and more likely to be found in plants.
Lysosomes
Membrane-bound vesicles that contain hydrolytic enzymes involved in intracellular digestion.
Breaks down materials ingested by cell.
Aids in renewing cells components by breaking down old ones and releasing components for reuse.
Autolysis- rupture of lysosome digesting cellular contents (“suicide”)
Microbodies
Membrane-bound organelles specialized as containers for metabolic reactions.
Two important types are peroxisomes and glyoxysomes.
Peroxisomes
Contain oxidative enzymes that catalyze a class of reactions in which hydrogen peroxide is produced by the transfer of a hydrogen from a substrate to an oxygen. Break fats down into smaller molecules that can be used for fuel. Used ion the liver to detoxify compounds harmful to the body.
Glyoxysomes
Found in fat tissue of germinating seedlings.
Used to convert fats into sugar until seedling is mature enough to produce sugar via photosynthesis.
Mitochondria
Sites of aerobic respiration (energy supply).
Semiautonomous - their own circular DNA and ribosomes, self replicate via binary fission.
Cell wall
Protects cell from external stimuli and desiccation.
Animal cells do not have cell wall.
Centrioles
Specialized type of microtubule involved in spindle organization during cell division.
Not bound by membrane.
Come in pairs oriented at right angles to each other and lie in region called centrosome.
Plant cells do not contain.
Cytoskeleton
Gives cell mechanical support, maintains it’s shape, functions in cell motility.
Composed of microtubules, microfilaments and intermediate filaments.
Microtubule
Hollow rods made of polymerized tubulins that radiate through cell and provide support.
Provide framework for organelle movement.
Cilia and flagella are special arrangements of microtubules involved in motility.
Microfilaments
Solid rods of actin.
Move materials across the plasma membrane.
Intermediate filaments
Collection of fibers involved in maintenance of cytoskeleton integrity.
Diffusion
Concentration gradient : high to low
Membrane protein required : no
Energy required : no- passive process
Type of molecules transported : small non-polar (O2, CO2…)
Osmosis
Concentration gradient : high to low
Membrane forgotten required : no
Energy required : no- passive process
Type of molecule transported : water
Facilitated transport
Concentration gradient : high to low
Membrane protein required : yes
Energy required : no - passive process
Type of molecule transported : large non-polar (glucose)
Active transport
Concentration gradient : low to high
Membrane protein required : yes
Energy required : yes, ATP
Type of molecule transported : polar molecules or ions ( Na+, Cl-, K+)
Endocytosis
Process in which cellular membrane invaginates, forming a vehicle that contains extracellular medium.
Pinocytosis- ingestion of fluids or small particles.
Phagocytosis- ingestion of large particles.
Exocytosis
When a vehicle within a cell fuses with the cell membrane and release it’s contents to the outside.
Tissues
Groups of morphologically and functionally related cells.
Epithelial tissue
Covers the surfaces of the bodies and lines the cavities.
Protect against injury, invasion or desiccation.
Involved in absorption, secretion and sensation.
Connective tissue
Involved in body support and other functions.
Includes: bone, cartilage, tendon, ligaments, adipose tissue and blood.
Nervous tissue
Composed of specialized cells called neuroses that are involved in perception, processing and storage of information.
Muscle tissue
Has great contractile capability and involved in movement.
Three types : skeletal muscle, cardiac muscle and smooth muscle.
Viruses
Unique acellular structures composed of nucleic acid enclosed by a protein coat.
Obligate intracellular parasites - can express genes and reproduce only inside a living cell.
Size of viruses, prokaryotes and eukaryotes
Viruses : 20 to 300 nm
Prokaryotes : 1 to 10 mm
Eukaryotes : 10 to 100 mm