unit two

Question 1

prokaryotes

Answer 1

NO nucleus
DNA in a nucleoid
cytosol
no organelles other than ribosomes 
small size
primitive 
Bacteria and Archaea

Question 2

Eukaryotes

Answer 2

Has nucleus and nuclear envelope
cytosol
membrane bound organelles 
much larger in size
Plant and animal size

Question 3

cells must be small to maintain a large…

Answer 3

surface area to volume ratio

ex) small intestine is highly folded to increase absorption of nutrients
ex) root hairs expansion of root epidermal cells; increase surface area for water and mineral absorption

Question 4

Nucleus

Answer 4

control center of the cell
contains DNA and is surrounded by nuclear envelope
nuclear pores control what enters and leaves
chromatin: complex of DNA and proteins. make up chromosomes
nucleolus: region where ribosomal subunits form

Question 5

Ribosomes

Answer 5

protein synthesis/creation
made of rRNA and protein
large subunit and small subunits
free: float in cytosol and produce cell used proteins
bound: attached to ER make proteins for export

Question 6

Endomembrane System

Answer 6

regulates protein traffic and performs metabolic functions
ER: network of membranes and sacs
rough has ribosomes on surface
smooth packages proteins for secretion, send transport to Golgi and make replacement
synthesize lipids, metabolize carbs detox drugs and poison and store Ca

Question 7

Golgi Apparatus

Answer 7

series of flattened membrane sacs (cisternal)
synthesis and packaging of materials (small molecules) for transport in vesicles protein to produce lysosome
cis face- receives vesicles
trans face- ships vesicles

Question 8

lysosomes

Answer 8

intracelular digestión that recycle cells materials. programmed cell death
contains hydrolytic enzymes

Question 9

vacuoles

Answer 9

storage of materials (food, water, minerals, pigments, poison)
membrane bound vesicle
plants have large and central vacuoles

Question 10

mitochondria

Answer 10

site of cellular respiration
double membrane: outer and inner
cristae- folds of inner membrane; contains enzymes for ATP production; increased SA to increase ATP
matrix: fluid filled inner compartment

Question 11

chloroplasts

Answer 11

site of photosynthesis
double membrane
thylakoid disks in stacks (grams) stroma (fluid)
contains chlorophyll (pigments) for capturing

Question 12

endosymbiont theory

Answer 12

mitochondria and chloroplasts share similar origin
eukaryotes engulfed prokaryotes .
evidence: double membrane, own ribosomes and DNA and reproduce independently

Question 13

peroxisomes

Answer 13

breaks down fatty acid; detox alcohol

involves production of hydrogen peroxide

Question 14

cytoskeleton

Answer 14

network of protein fibers

support, mobility regulate biochemical activities

Question 15

extracellular matrix

Answer 15

outside plasma membrane
composed of glycoproteins (ex. collagen)
strengthens tissues and transmits external signals to cell

Question 16

intercellular junctions (animal cells)

Answer 16

tight junctions- 2 cells are fused to form watertight seal
desmosomes- rivets that fasten into strong sheets
gap sheets- channels through which ions, sugar, small molecules can pass

Question 17

plant cells organelles

Answer 17

cell wall- protect plant, maintain shape
composed of cellulose

plasmodesmata- channels between cells that let molecules pass

Question 18

cell membrane-

Answer 18

selective permeability

fluid mosaic model (membrane of phospholipids and proteins and carbs held together by weak interactions)

Question 19

phospholipids

Answer 19

amphipathis- hydrophilic phosphate head and hydrophobic fatty acid tails
hydrophobic barrier keeps hydrophilic molecules out

Question 20

membrane fluidity

Answer 20

low temps: phospholipids with unsaturated tails (kinks prevent close packaging)
cholesterol- limits fluidity at high temps, also hinder close packing at low temps

Question 21

integral proteins

Answer 21

embedded in membrane
determined by freeze fracture
transmembrane with hydrophilic heads and hydrophobic middles

Question 22

peripheral proteins

Answer 22

extracellular or cytoplasmic sides of membrane
NOT embedded
held in place by cytoskeleton or ECM
provides storage framework

Question 23

passive transport

Answer 23

no ATP needed
diffuses DOWN the concentration gradient
E.g. hydrocarbons, CO2, O2, H2O

Question 24

osmosis

Answer 24

lower solute concentration to higher concentration
osmoregulation- control of water balance
Hypertonic- higher concentration of solutes
Hypotonic- higher concentration of solvent
Isotonic- equal concentration of solute/solvent

Question 25

facilitated diffusion

Answer 25

transport proteins help hydrophilic substances cross

aquaporin: channel proteins for water

Question 26

active transport

Answer 26

requires energy (ATP)
proteins transport substances against concentration gradient
E.g. Na/K pump, proton pump

Question 27

cotransport

Answer 27

memrane protein enables “downhill” diffusion of one solute to drive “uphill” diffusion of another

Question 28

bulk transport

Answer 28

endocytosis: large molecules in
- form new vesicles
exocytosis: large molecules out
- vesicles fuse with cell membrane and expel contents

phagocytosis: cell eating solids
pinocytosis: cellular drinking fluids
receptor mediated endocytosis: ligands bind to specific receptors on cell surface