lecture notes exam 1

3 metabolic pathways

1. glycolysis

2. cellular respirator

3. fermentation

glycolysis

glucose converted to pyruvate

cellular respiration

aerobic converted pyruvate into H2O and CO2 which leads to much synthesis of ATP

fermentation

anaerobic converted pyruvate to lactic acid or ethanol + CO2 (little ATP produced)

what starts the other metabolic pathways?

glycolysis

what do all glucose oxidation reaction involve?

electron transfer reaction (redox)

e- from glucose is transferred to other molecule

where are metabolic pathways in eukaryotic cells?

compartmentalized in organelles

cellular respiration

synthesis ATP- endergonic

glucose oxidation provides energy

what is the main energy currency in cells?

ATP

energy with exergonic and endergonic reactions

energy released by exergonic reactions is stored in bonds of ATP

when ATP is hydrolyzed-free energy is released to drive endergonic

true or false: reduction and oxidation always occur together

true

NAD

key electron carrier in redox reaction

what happens when NAD is reduced and oxidized?

oxi: receive e- from glucose

red: carries e- from glucose to other molecule in mitochondria

what are the inputs and outputs for glycolysis?

inputs: glucose, 2 NAD+, 2 ADP + 2 Pi

outputs: 2 mol of pyruvate, 2 NADH, 2 ATP

10 enzyme catalyzed reactions

reactions 1-5: energy investment, adding P to glucose

reactions 6-10: energy payout in NADH and 2 ATP

if oxygen is present what starts?

pyruvate oxidation and citric acid cycle

pyruvate oxidation

links glycolysis (in cytoplasm) and citric acid cycle (in mitochondria)

where does pyruvate oxidation occur?

liquid mitochondrial matrix

how many reactions in the citric acid cycle?

8 reactions beginning with acetly coA

what are the inputs and outputs of the citric acid cycle?

inputs: acetyl CoA, electron carrier NAD+ and FAD, GDP

outputs: CO2, reduced electron carriers (NADH and FADH2), GTP

oxidative phosphorylation

involves protein and electron carrier molecule imbedded in mitochondrial inner membrane

2 interconnected stages of oxidative phosphorylation

1. electron transport chain (ETC)

2. chemiosmosis

electron transport chain

e- from NADH and FADH2 pass through respiratory chain of inner membrane carriers

4 protein complexes (i, ii, iii, iv) oxygen final electron acceptor

NADH and FADH2 give up energetic electron and oxidized NAD+ and FAD can be recycled

chemiosmosis

protons (H+) diffuse back into mitochondria through ATP synthase, a channel protein

diffusion coupled to ATP pynthesis

how does oxidative phosphorylation form ATP?

as e- from NADH and FADh move through ETC energy is released

energy then used to transport protons against concentration gradient

proton motive force later drives proton back across membrane (p move through ATP synthase channel)

ATP synthase

H+ flows from inter-membrane through synthase to matrix

ADP + Pi ———→ ATP

lactic acid fermentation

pyruvate is electron acceptor (becomes reduced)

oxidizes NADH back to NAD so more glycolysis can occur

lactate is produce and no additional ATP is made

alcoholic fermentation

requires 2 enzymes to metabolize pyruvate to ethanol

CO2 product waste

intermediate acetaldehyde is reduced by NADH + H+ to produce NAD+ and glycolysis content

catabolic pathways

break down products to eventually enter aerobic respiratory pathway

carbohydrates, lipids, protein, and nucleic acid

carbohydrate catabolic pathway

polysaccarides are hydrolyzed to monoaccarides which enter glycolysis

lipid catabolic pathway

triglycerides are hydrolyzed to glycerol and fatty acids

fatty acids converted to acetyl CoA by B oxidation and acetyl CoA enters citric acid cycle

protein catabolic pathway

proteolysis hydrolyzes to amino acid which are converted to molecules that enter glycolysis or citric acid cycle

nucleic acid catabolic pathway

hydrolyzed to nucleotides which are further broken down into phosphate groups, bases, and sugars- enter glycolysis

true or false: anabolic pathways are often reversals of catabolic pathways

true

is photosynthesis endergonic or exgergonic?

endergonic, anabolic process

how does photosynthesis convert energy?

radiant energy to chemical energy

what types of reactions does photosynthesis involve?

redox reaction

CO2 reduced to form carbohydrates

H2O oxidized to form oxygen

what are the 2 pathways of photosynthesis?

1. light reactions: convert light energy to chemical energy as ATP and NADPH

2. light-dependent reaction: use ATP and NADPH plus CO2 to produce carbohydrates

exciting a mol

1. scatter- photon bounce off mol

2. transmitted- photon passes through mol

3. absorb- mol acquire energy of photon

what are the main pigments absorbing light for photosynthesis

chlorophylls and cartenoids

molecular structure of chlorophyll

several types of thylakoid pigments

• chlorophylls a and b

• accessory pigments

pigments arranged antenna systems

photosystems

photosystem

consist of multiple antenna and their pigments and surrounds reaction center

key events of light reactions

• ps reaction center Chl absorbs photon and becomes excited Chl*

• Chl* donates an e- to acceptor molecule A

• A is first in chain of electron carriers in thylakoid membrane

• final receptor is NADP+ and becomes NADPH

photosystem I

light energy reduces NADP+ to NADPH

reaction center has P700 chlorophyll a molecule

photosystem II

light energy oxidizes water——> O2, H+ and electrons

P680 chlorophyll a molecule

2 systems of electron transport

noncyclic: produce NADPH and ATP (light energy used to oxidize water)

cyclic: produce ATP only (use light to make more ATP)

what drives photophosphorylation?

both noncyclic and cyclic electron transportation

what happens when cells exchange material with the environment?

nutrient in——> distribution——→ cell metabolism——> metabolic waste out

as cells increase

cell volume increases but SA/vol ratio decreases with increased cell dimension

what physical factors influence rate?

• diameter molecule or ion

• electrical charge

• temperature solution

• concentration gradient

what are the functions of biological membranes?

1. boundaries

2. regulators

3. intracellular transporters

4. cell identification, communication, and adhesion

5. contain and restrict some biochemical reactions

how does membrane fluidity vary in lipid composition?

phospholipids vary in terms of fatty acid chain length, degree of saturation, and polar groups

how is the degree of membrane fluidity influenced?

by lipid composition

• short

• unsaturated chains increase fluidity

• cholesterol alters interaction among fatty acid side chains

• temperature fluidity decreases in cold conditions

how do membranes get across a cell membrane?

cell membranes has selective permeability and use active and passive transport

passive transport

movement by diffusion

no outside energy

concentration gradient is driving force

what are the 2 kinds of passive transport?

simple diffusion- directly across phospholipid bilayer

facilitated diffusion- across membrane via channel or carrier protein

active transport

movement against a concentration gradient via protein pump that require energy to operate

what are the 2 kinds of active transport?

primary: direct hydrolysis of ATP

secondary: energy comes form ion concentration gradient established by primary

osmosis

diffusion of water across membrane that the solutes cannot pass through

water molecules diffuse from regions of higher water concentration (lower solute) to lower water concentration (higher solute)

what does osmosis depend on?

number of solute particles present not type

osmotic pressure

pressure that must be applied to a solution to prevent flow of water across a membrane by osmosis

osmolarity

solute particles per liter of water

tonicity

relative concentration of solutes on either side of membrane

determines direction and extent of net water movement

what are the types of tonicity?

isotonic, hypotonic, and hypertonic

isotonic

solutions have equal solute concentrations

hypotonic

solution has lower solute concentration

hypertonic

solution has higher solute concentration

water channel aquaporins

water can cross membrane directly or by hitchhike with hydrated ions

is the Na+ K+ pump present in all cells?

yes, pumps Na+ out against gradient and pumps K+ in

why is the Na+ K+ pump important?

important for maintaining membrane potential and stabilizes cell volume

where is Na+ more present?

Na+ higher outside cell

K+ higher inside the cell

does the Na+ K+ pump use ATP?

yes, uses ATP directly to pump both ions

is the Na+ K+ pump primary or secondary active transport?

primary

glucose NA+ transporter

glucose transported across membrane against concentration gradient

movement Na+ provide energy to move glucose molecules

is the glucose Na+ transporter primary or secondary active transport?

secondary

how does the Na+ K+ pump and glucose Na+ transporter work together?

they work parallel to each other

what happens when macromolecules are too large to cross plasma membrane?

taken in or secreted by membrane vesicles

endocytosis or exocytosis

endocytosis

plasma membrane surround material and invaginates form vesicle

exocytosis

material in vesicle expelled (secrete) from cell by fusion with plasma membrane

why is membrane fluidity important during membrane vesicles?

key to sealing events that occur during vesicular fusion and membrane invagination

what are the different variations of endocytosis?

phagocytosis, pinocytosis, and receptor-mediated

phagocytosis

engulf large particles

pinocytosis

small dissolved substances or fluid

receptor mediated

highly specific

involves receptor proteins- integral membrane protein bind to specific substance

where are receptors located in receptor mediated endocytosis?

coated pits where coated with other protein like clathrin

what are the functions of the cytoskeleton?

• supports and maintain cell shape

• holds organelles in position

• moves organells in cytoplasm

• interact with extracellular structures to hold cell in place

what are the 3 filamentous networks that the cytoskeleton is composed of?

microfilaments

microtubules

intermediate filaments

microfilaments

• help cell or part of cell to move and determines shape

• made from protein actin + - ends and polymerizes to form helical chains

• motor protein: myosin

microtubules

• form rigid internal skeleton in some cells

• act as framework for motor proteins

• made from protein tubulin a dimer ( + - ends)

• can change length rapidly by adding or losing dimers

intermediate filaments

fibrous subunits, tough

what happens to the motor protein for microtubules?

undergo reversible shape change powered by ATP hydrolysis

move - to + kinesin

move + to - dynein

what are cilia and eukaryotic flagella made of?

microtubules

cilia vs flagella

cilia: short, many present, move with stiff power stroke and flex recovery stroke

flagella: longer, 1-2 present, movement snakelike

what are cell walls made of?

cellulose, chitin, or protein

extracellular matrix

• made of collagen and gel-like proteoglycans

• hold cell together in tissue and contribute physical properties

• help filter materials passing between different tissues

• help orient cell movement during embryonic development and tissue repair

3 types of cell junctions

1. tight junction: cell adhesion and sealing

2. desmosomes: cell adhesion without sealing

3. gap junction: cell adhesion and molecules move between cells

what are common features of all cells?

• plasma membrane

• cytoplasm

• genome of DNA

• ribosomes

how are prokaryotic and eukaryotic cells classifed?

based on internal organisms

prokaryotic cells (bacteria and archea)

genomes consist of 1-2 molecules of DNA concentrated in a nucleoid

exterior:

• rigid cell wall

• some additional outer membrane or slimy capsule or flagella

interior:

• lack nucleus and membrane enclosed internal compartmentalization

• protein structures separate certain substrate from others in cell

• tiny encapsulin nano compartment enclose a single protein

• some cell function occur in cell regions separated by cytoskeleton

which cells are smallest and simpilest?

prokaryotic