Chapter 3: Cells: The Living Units

Question 1

Cell theory

Answer 1

• Cell is basic structural and functional unit
• -activity depends on both individual and collective activity of cell
• Biochem activities are dictated by subcellular structure
• Basis of continuity of life (generation to generation)

Question 2

3 main parts of generalized cell

Answer 2

Plasma membrane (separates intracellular compartments from extracellular fluid), cytoplasm (intracellular fluid, includes all organelles except nucleus), nucleus

Question 3

Structure of plasma membrane

Answer 3

bilayer with hydrophobic tail and hydrophillic head, cholesterol, gylcolipid, rafts (for cell signaling molecules)

Question 4

Transport proteins

Answer 4

allows hydrophylic solutes to cross hydrophobic membrane via channel

Question 5

Hormone/Neurotransmitter receptors

Answer 5

binding of signaling molecule to protein –> triggers change in structure –> change in function (activation or inactivation)

Question 6

Attachment for cytoskeletal or extracellular matrix proteins

Answer 6

anchoring points for intracellular structural proteins (cytoskeleton) or extracellular matrix proteins

Question 7

Intercellular adhesion

Answer 7

in some proteins; complementary docking sites for joining adjacent cells and promote cell-cell interaction

Question 8

cell-cell recognition

Answer 8

glycoproteins as identification tags

Question 9

Tight junctions

Answer 9

form a seal between adjacent cells

Question 10

Demosomes

Answer 10

mechanically anchor cells to each other; like velcro; interlock

Question 11

gap junctions

Answer 11

hexameric protein complexes that form a pore between cells; can selectively pass molecules or ions; act together as functional unit

Question 12

Passive transport

Answer 12

occurs without energy input from cell; SIMPLE DIFFUSION for non polar and lipid soluble substances, FACILITATED DIFFUSION with carrier proteins for polar molecules and ions (glucose, amino acid, etc), OSMOSIS for water molecules

Question 13

Active transport

Answer 13

metabolic energy input (ATP) is necessary

Question 14

Osmolarity

Answer 14

total concentration of solute particles in a solution

Question 15

Tonicity

Answer 15

how solution affects cell volume; in osmosis

Question 16

Isotonic solution

Answer 16

The concentration of solutes is equal inside and outside the cell so water moves across the membrane in both directions maintaining cell size

Question 17

Hypotonic solution

Answer 17

the solution has a lower solute concentration than the cell so water moves into the cell causing plant cells to swell and animal cells to swell and burst

Question 18

Hypertonic solution

Answer 18

The solution has a higher solute concentration than the cell so water moves out of the cell and into the solution causing the cell to plasmolyze

Question 19

Symport system

Answer 19

Active transport with two solutes moved in same direction

Question 20

Antiport system

Answer 20

Active transport where two solutes are moved in opposite direction

Question 21

Primary active transport

Answer 21

hydrolysis of ATP directly phosphorylates transport protein, conformational change, transport

Question 22

Secondary active transport

Answer 22

use of exchange pump (such as sodium potassium pump) to indirectly drive transport

Question 23

Vesicular Transport

Answer 23

• requires energy from ATP or GTP hydrolysis

- mechanism to transport large particles and macromolecules

Question 24

Transcytosis

Answer 24

(vesicular transport) moving substances into, through, then out of the cell

Question 25

Vesicular trafficking

Answer 25

moving substances from one area inside the cell to another

Question 26

Phagocytosis

Answer 26

external environment, engulfs into phagosome, destroys with lysosome

Question 27

Membrane potential

Answer 27

voltage (electrical potential difference) across member

Question 28

Resting membrane potential

Answer 28

when not stimulated, ranges from -50 to -100mV, results from sodium and potassium gradients and differential permeability

Question 29

Cell Adhesion Molecules (CAM)

Answer 29

Membrane glycoproteins, functions include proper embryonic dev of tissues, wound repair, etc)

Question 30

Contact Signaling

Answer 30

physical contact between membrane receptors; normal dev and immunity

Question 31

Electrical signaling

Answer 31

voltage regulated ion gates; nerve + muscle tissue

Question 32

Chemical signaling

Answer 32

neurotransmitters or hormones (ligands) bind with high specificity to receptors in plasma membrane --> structural change --> ion channels or enzymatic activity; with g protein linked receptors, activates g protein and second messenger

Question 33

Ribosomes

Answer 33

contain protein and rRNA; site of protein synthesis

Question 34

Rough ER

Answer 34

External surface studded with ribosomes; makes all secreted proteins, integral membrane proteins and phospholipids

Question 35

Smooth ER

Answer 35

in liver: lipid and cholesterol metabolism in testes/ovaries: synthesis of steroid hormones in intestinal cells: absorption, synthesis, and transport of fats in skeletal and cardiac muscle, store and release of CALCIUM IONS

Question 36

lysosomes

Answer 36

spherical membranous bags containing digestive enzymes in acidic solution; garbage men of cell; breakdown/degrade

Question 37

Endomembrane system

Answer 37

produce, store, export bio molecules; degrade/detoxify harmful substances

Question 38

Cytoskeleton

Answer 38

Microfilaments, intermediate filaments, microtubules; structural protein rods in cytosol

Question 39

Centrioles

Answer 39

Mitotic spindle during mitosis

Question 40

Ciliary motion vs coordinated ciliary motion

Answer 40

ciliary motion has recovery stroke

Question 41

Pore complexes

Answer 41

in nuclear envelope to regulate transport of large molecules in and out of nucleus

Question 42

nucleoli

Answer 42

ribosome production

Question 43

chromatin

Answer 43

strands of DNA complexed with histone proteins; positive charge; functional units=nucleosomes;form condensed chromosomes when nucleus starts to divide

Question 44

Cell growth and division

Answer 44

``` INTERPHASE G1: Growth (G0 cells cease dividing here) S: Synthesis (DNA replication) G2: Growth MITOTIC PHASE Mitosis Cytokinesis ```

Question 45

Helicase

Answer 45

enzyme that unzips DNA

Question 46

Mitosis

Answer 46

Prophase Metaphase Anaphase Telophase

Question 47

Early prophase

Answer 47

chromatin condenses to chromosomes, nucleolus disappears, mitotic spindles start growing

Question 48

Late prophase

Answer 48

nuclear envelope breaks up, spindle microtubule (kinetochure) attaches to centromere; spindle microtubules (polar) meet in middle and push centrioles to opposite sides of cell

Question 49

Metaphase

Answer 49

chromosomes line up at metaphase plate, separase enzyme cuts kinetochore protein

Question 50

Anaphase

Answer 50

chromatids pulled apart

Question 51

Telophase

Answer 51

new nuclear envelope and nucleolus; microtubule spindles break down and disappear --> cytokinesis

Question 52

Factors that control cell division

Answer 52

- suface to volume ratio - chem signales (growth factors; hormones) - contact inhibition - cyclins and cyclin-dependent kinases (Cdks) - cell division inhibited by repressive genes (cancer does not have)