The Cell

Question 1

The cell theory can be summarized as

Answer 1

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.

Question 2

The three primary methods available to study the cell and it’s structures are

Answer 2

Microscopy, autoradiography and centrifugation

Question 3

The compound light microscope is used in

Answer 3

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.

Question 4

Phase contrast microscope

Answer 4

Used to study living specimens.

Differences in refractive index are used to produce contrast between cellular structures.

Question 5

Electron microscope

Answer 5

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.

Question 6

Autoradiography

Answer 6

Uses radioactive molecules to trace and identify cell structures and biochemical activity ( such as protein synthesis)

Question 7

Centrifugation

Answer 7

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.

Question 8

Prokaryotes

Answer 8

Bacteria and cyanobacteria.
Contain cell wall.
No nucleus.
Ribosomes ( subunits = 30s and 50s)
No membrane bound organelles.

Question 9

Eukaryotes

Answer 9

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

Question 10

Cell membrane

Answer 10

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.

Question 11

Nucleus

Answer 11

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.

Question 12

Nucleolus

Answer 12

Dense structure in nucleus where ribosomal RNA (rRNA) synthesis occurs.

Question 13

Ribosomes

Answer 13

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

Question 14

Endoplasmic reticulum

Answer 14

network of membrane enclosed spaces connected at points with the nuclear membrane.
With ribosomes - rough ER
Without ribosomes - smooth ER

Question 15

Endoplasmic reticulum is involved in

Answer 15

Transport of materials through the cell.
Smooth ER- involved in lipid synthesis and detoxification of drugs and poisons.
Rough ER- involved in protein synthesis

Question 16

Bound ribosome synthesize proteins which then

Answer 16

cross into cisternae of RER and undergo chemical modification.
Then cross into smooth ER, secreted into cytoplasmic vesicles and transported to Golgi apparatus

Question 17

Golgi apparatus

Answer 17

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.

Question 18

Vesicles and vacuoles

Answer 18

Membrane-bound sacs involved in transport and storage.

Vacuoles are larger than vesicles and more likely to be found in plants.

Question 19

Lysosomes

Answer 19

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”)

Question 20

Microbodies

Answer 20

Membrane-bound organelles specialized as containers for metabolic reactions.
Two important types are peroxisomes and glyoxysomes.

Question 21

Peroxisomes

Answer 21

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.

Question 22

Glyoxysomes

Answer 22

Found in fat tissue of germinating seedlings.

Used to convert fats into sugar until seedling is mature enough to produce sugar via photosynthesis.

Question 23

Mitochondria

Answer 23

Sites of aerobic respiration (energy supply).

Semiautonomous - their own circular DNA and ribosomes, self replicate via binary fission.

Question 24

Cell wall

Answer 24

Protects cell from external stimuli and desiccation.

Animal cells do not have cell wall.

Question 25

Centrioles

Answer 25

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.

Question 26

Cytoskeleton

Answer 26

Gives cell mechanical support, maintains it’s shape, functions in cell motility.
Composed of microtubules, microfilaments and intermediate filaments.

Question 27

Microtubule

Answer 27

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.

Question 28

Microfilaments

Answer 28

Solid rods of actin.

Move materials across the plasma membrane.

Question 29

Intermediate filaments

Answer 29

Collection of fibers involved in maintenance of cytoskeleton integrity.

Question 30

Diffusion

Answer 30

Concentration gradient : high to low
Membrane protein required : no
Energy required : no- passive process
Type of molecules transported : small non-polar (O2, CO2…)

Question 31

Osmosis

Answer 31

Concentration gradient : high to low
Membrane forgotten required : no
Energy required : no- passive process
Type of molecule transported : water

Question 32

Facilitated transport

Answer 32

Concentration gradient : high to low
Membrane protein required : yes
Energy required : no - passive process
Type of molecule transported : large non-polar (glucose)

Question 33

Active transport

Answer 33

Concentration gradient : low to high
Membrane protein required : yes
Energy required : yes, ATP
Type of molecule transported : polar molecules or ions ( Na+, Cl-, K+)

Question 34

Endocytosis

Answer 34

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.

Question 35

Exocytosis

Answer 35

When a vehicle within a cell fuses with the cell membrane and release it’s contents to the outside.

Question 36

Tissues

Answer 36

Groups of morphologically and functionally related cells.

Question 37

Epithelial tissue

Answer 37

Covers the surfaces of the bodies and lines the cavities.
Protect against injury, invasion or desiccation.
Involved in absorption, secretion and sensation.

Question 38

Connective tissue

Answer 38

Involved in body support and other functions.

Includes: bone, cartilage, tendon, ligaments, adipose tissue and blood.

Question 39

Nervous tissue

Answer 39

Composed of specialized cells called neuroses that are involved in perception, processing and storage of information.

Question 40

Muscle tissue

Answer 40

Has great contractile capability and involved in movement.

Three types : skeletal muscle, cardiac muscle and smooth muscle.

Question 41

Viruses

Answer 41

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.

Question 42

Size of viruses, prokaryotes and eukaryotes

Answer 42

Viruses : 20 to 300 nm
Prokaryotes : 1 to 10 mm
Eukaryotes : 10 to 100 mm