BIOLOGY 160 EXAM #2

selective permeability

allows some substances to cross more easily than others

phospholipids

key ingredient of biological molecules

spontaneously self-assemble into simple membranes

diffusion

tendency for particles of any substance to spread out into available space

concentration gradient

diffuses down it when net movement from more concentrated to less concentrated side

equilibrium

molecules still move back and forth; no net change in concentration on either side

passive transport

when molecules diffuse across membrane

polar molecules diffusion

diffuse across hydrophobic interior if theyre moving down concentration gradient and have transport proteins

nonpolar molecules diffusion

diffuse easily across phospholipid bilayer

osmosis

diffusion of water across selectively permeable membrane

tonicity

refers to ability of a surrounding solution to cause a cell to gain or lose water

animal cell in isotonic solution

volume remains constant

animal cell in hypotonic solution

cell gains water; swells and may burst

animal cell in hypertonic solution

cell shrivels and can die from water loss

osmoregulation

control of water balance

plant cell in hypotonic

turgid (firm)

healthy state

turgor pressure

prevents cell from taking in too much water and bursting

plant cell in isotonic

no net movement of water into cell, cell is flaccid (limp)

plant cell in hypertonic

loses water, shrivels, plasma membrane pulls away from cell wall

plasmolysis

causes plant to wilt and can be lethal in hypertonic solution

bacteria and fungi also plasmolyze

facilitated diffusion

assisted transport; type of passive transport bc no energy needed

driving force is concentration gradient

used by sugars, amino acids, ions, and water

aquaporins

allow only water molecules to pass thru them

found in bacteria, plants, and animals

active transport

cell must expend energy to move solute against concentration gradient

ATP supplies the energy

allows cells to maintain internal concentrations of small molecules and ions that are different from surroundings

model of active transport system

1. solute molecule on cytoplasmic side attach to specific binding sites on transport protein

2. energy provided by ATP, transport protein changes shape in a way that solute is released on other side of membrane

3. transport protein returns to original shape, ready for next passengers

exocytosis

export BULKY materials like proteins and polysaccharides

-transport vesicle filled with large molecules comes from golgi apparatus to plasma membrane

-vesicle fuses with plasma membrane and vesicles contents spill out of cell when vesicle membrane becomes part of plasma membrane

endocytosis

process thru which cell takes in LARGE molecules

phagocytosis (type of endocytosis)

"cellular eating"

-cell engulfs particle by wrapping extensions (pseudopodia) around it and packaging it within a vacuole

-vacuole fuses with lysosome

-hydrophilic enzymes digest contents of the vacuole

used by protists and white blood cells

receptor-mediated endocytosis (other type of endocytosis)

-enables a cell to acquire specific solutes

-receptor proteins are embedded in regions of the membrane lined by layer of coat proteins

-plasma membrane indents to form coated pit, receptor proteins pick up particular molecules from extracellular fluid

-coated pit pinches closed to form a vesicle, which releases molecules into the cytoplasm

-our cells use it to take in cholesterol from the blood for making membranes a precursor for other steroids

LDL's

low density lipoproteins

bind to receptor proteins and enter cells by endocytosis

cholesterol uses it to circulate in blood

energy

the capacity to cause change or perform work

kinetic

energy of motion

thermal energy

type of kinetic energy

random movement of atoms/molecules

heat

thermal energy in transfer from one object to another

potential energy

matter possesses as a result of its location or structure

chemical energy

potential energy available for release in a chemical reaction

most important energy for living things

can be transformed to power the work of a cell

thermodynamics

study of energy transformations that occur in a collection of matter

open system

exchanges both energy and matter with surroundings

1st law

energy in universe is constant; energy can be transferred or transformed; cannot be created nor destroyed

during every transfer/transformation, some energy becomes unavailable to do work, converted to thermal energy and released as heat

entropy

measure of disorder/randomness

more randomly arranged, more entropy

2nd law

energy conversions increase the entropy of the universe

cellular respiration

chemical energy in organic molecules is used to make ATP

waste products are CO2 and H2O

34% of chemical energy is used for work; 66% is lost as heat

exergonic

releases energy

begins with reactants whose covalent bonds contain more potential energy than those in the products

rxn releases to surroundings, the amount of energy equal to the difference in potential energy between reactants and products

endergonic

requires a net input of energy and yield products rich in potential energy

starts with reactants containing little potential energy, energy is absorbed from surroundings as reaction occurs; products have more chemical energy than reactants did

photosynthesis

endergonic; starts with energy poor reactants (CO2 and H2O) and using energy from sun, produce energy-rich sugar molecules

metabolism

total of organism chemical reactions

metabolic pathway

series of chemical reactions that builds complex molecule or breaks down a complex molecule into a simpler one

energy coupling

use of energy released from exergonic rxns to drive endergonic reactions- crucial to ALL cells!

ATP is key to energy coupling

ATP

powers cellular work

bonds between phosphate groups are unstable and can be broken by hydrolysis

hydrolysis of ATP is exergonic

ATP is renewable

phosphorylation

phosphate transfer

activation energy

amount of energy needed to move uphill to a higher energy, unstable state

enzymes

molecules that function as catalysts, increasing rate of a reaction without being consumed by it

almost all enzymes are proteins

lower the activation energy needed

substrate

thing acted on

active site

substrate fits into

Catalytic cycle

1. starts with empty active site

2. substrate attaches by weak bonds, active site changes shape to fit it more snugly

3. substrate is converted to products

4. the products are released

inhibitor

chemical that interferes with enzymes activity

competitive inhibitor

reduces an enzymes productivity by blocking substrate molecules from entering the active site

can be overcome by adding greater concentration of substrate

noncompetitive inhibitor

does not enter active site

binds to site elsewhere on enzyme, its binding causes enzymes active site shape to change and no longer fit substrate

feedback inhibition

if a cell is making more than it needs, the product may act as an inhibitor until its used up by the cell and the pathway functions again

photosynthesis

atoms of CO2 and H2O are rearranged to produce sugar and oxygen

cellular respiration

o2 is consumed as sugar is broken down to CO2 and H2O

takes place in mitochondria of eukaryotes

chemical energy of the bonds in glucose is released and stored in the chemical bonds of ATP

produces 32 ATP's for each glucose

kilocalories (kcal)

measure of the amount of heat needed to raise temp. of 1 kg of water by 1 degree celsius

redox reaction

movement of electrons from one molecule to another

oxidation

loss of electrons

reduction

addition of electrons

Cellular resp.

glucose loses electrons as its oxidized to CO2

O2 gains electrons as its reduced to H2O

NAD+

coenzyme; accepts electrons and reduced to NADH

used to shuttle electrons in redox reactions

electron transport chain

built into inner membrane of mitochondria; electrons pass from carrier to carrier, releasing energy to make ATP

in prokaryotic cells that use aerobic respiration...

the cellular respiration steps occur in cytosol and ETC is in the plasma membrane

glycolysis

in cytosol

begins with one molecule of glucose (6C) and ends with two molecules of pyruvate (3C each)

2 molecules NAD+ reduced to 2 molecules NADH;

ATP formed during substrate-level phosphorylation (ADP+P=ATP)

oxidation of glucose to pyruvate releases energy which is stored in ATP and NADH

net gain:

2 ATP per glucose, 2 pyruvate, 2 NADH

glycolysis steps 1-4: energy investment phase

consume energy

2 molecules ATP used to energize a glucose, which is then split into 2 small sugars

glycolysis steps 5-9: energy payoff phase

yield energy for the cell

2 NADH produced for each glucose, 4 ATP made

major "chemical grooming" of pyruvate

pyruvate itself doesnt enter citric acid cycle; pyruvate from glycolysis transported from cytosol to mitochondrion

large multi enzyme complex:

1. carboxyl group (-COO) removed from pyruvate and given off as CO2

2. 2-carbon compound remaining is oxidized while molecule of NAD+ is reduced to NADH

3. conenzyme A joins with 2 carbon group, to form acetyl CoA

citric acid cycle (krebs cycle)

acts as metabolic furnace that oxidizes the acetyl CoA

only 2-carbon acetyl part of acetyl CoA enters the citric acid cycle-coenzyme A splits off and is recycled

2-carbon acetyl group is joined to 4-carbon molecule... the 6-carbon molecule (citrate) goes through redox rxn's

2 carbon atoms removed as CO2, the remaining 4-carbon molecule is regenerated

2 molecules of acetyl CoA are processed for each glucose... two turns of the cycle occur

overall yield per glucose: 2 ATP, 6 NADH, 2 FADH2

oxidative phosphorylation

this is where the most ATP is prpduced

uses ETC and chemiosmosis

ETC built into inner mitochondrial membrane

the cristae (folds) increase surface area

include:

thousands of copies of the ETC

multiple copies of ATP synthase enzyme

electrons are transported on NADH and FADH2 to oxygen, the final electron acceptor of cellular respiration

each oxygen atoms accepts 2 electrons from chain and picks up 2 H+ from surrounding solutions, which forms H2O

carriers bind/release during redox reactions, passing electrons down the energy hill

some use the energy released from electron transfers to actively move H+ across membrane

chemiosmosis

process that uses the energy stored in hydrogen ion gradient across membrane to drive ATP synthesis

H+ concentration gradient stores potential energy

ATP synthase is like a turbine; rush of H+ ions turns the wheels to do work

ions move one by one into binding sites; after once around, theyre spit out into mitochondrial matrix

the spinning turns internal rods, activates sites in the catalytic knob that phosphorylate ADP to ATP

atp to glucose ratio

32 ATP molecules per glucose altogether from cellular respiration

fermentation

way to harvest chemical energy that doesnt require oxygen

glycolysis uses no oxygen

provides anaerobic path for recycling NADH back to NAD+

lactic acid fermentation

NADH is oxidized back to NAD+ as pyruvate is reduced to lactate

ex: muscle cells use it when need for ATP outpaces delivery of O2

alcohol fermentation

yeasts and some bacteria recycle their NADH back to NAD+, while converting pyruvate to CO2 and ethanol

ethanol is toxic to those that produce it, so they release alcohol wastes to surroudings

obligate anaerobes

they require anaerobic conditions; poisoned by oxygen

ex: prokaryotes in stagnant ponds and deep in the soil

facultative anaerobes

can make ATP either by fermentation or oxidative phosphorylation

ex: our muscle cells

biosynthesis

production of organic molecules using energy-requiring metabolic pathways

if ATP accumulates...

it inhibits an early enzyme in glycolysis, slowing down respiration

chloroplasts

capture light energy from sun

in mesophyll

membranes in chloroplasts form framework, where many of the reactions of photosynthesis occur

envelope of 2 membranes enclose an inner compartment, filled with thick fluid called stroma

photosynthesis

allows plants to use solar energy to convert CO2 and H2O to sugars; release O2 as by-product

autotrophs

make their own food (plants)

ultimate source of organic molecules for almost all other organisms

photoautotrophs

use energy of light

producers of the biosphere (plants and other photosynthesizers)

producers feed the consumers

heterotrophs

cannot make their own food, but consume plants or animals or decompose organic material

endosymbiosis

chloroplasts originated from photosynthetic prokaryote that took up residence inside a eukaryotic cell

chlorophyll

gives leaves it green color

light-absorbing pigment in chloroplasts that plays role in converting solar to chemical energy

mesophyll

green tissue in interior of leaf

each mesophyll has numerous chloroplasts

stomata

tiny pores that let CO2 enter and O2 exit

veins

water absorbed by roots delivered to leaves through veins

also use veins to export sugars to roots and other parts of the plant

stroma

thick fluid in inner compartment of chloroplast

in stroma:

thylakoids

thylakoids

system of interconnected sacs

have machinery that convert light to chemical energy, used in stroma to make sugars

thylakoid space

internal compartment in thylakoids

grana

stacks of thylakoids

chlorophyll

built into thylakoid membranes

photosynthesis

6CO2+6H2O---->C6H12O6+6O2

Niel's discovery

in plants, H2O is split

Hydrogen is incorporated into sugars and O2 is released as gas

O2 comes from water

oxygen atoms come from CO2

how are photosynthesis and cellular respiration opposites?

photosynthesis: CO2 reduced to sugar; H2O oxidized to O2

requires energy

cellular respiration: sugar oxidized to CO2; O2 reduced to H2O

releases chemical energy