BIOL 1406 - Lecture Exam 2

Eukaryotic cytoskeleton

network of fibers that organizes structures and activities in the cell. functions in structural support for the cell and in motility and signal transmission

components are made of protein: microfilaments, intermediate filaments, and microtubules

Microfilaments

thin rods made of actin that function in muscle contraction , amoeboid movement, cytoplasmic streaming, and support of microvilli

Intermediate filaments

support cell shape and fix organelles in place, made of keratin proteins

Microtubules

shape the cell, guide organelle movement, and separate chromosomes in dividing cells

form core structure of cilia and flagella

Extracellular matrix

a non-cellular network of proteins and polysaccharides that surrounds and supports cells in tissues and organs

Composed of mostly collagen

Plasmodesmata

microscopic channels in plant cell walls that connect the cytoplasm of adjacent cells, allowing for the movement of water, ions, and molecules

Tight junctions

this junction establishes a barrier that prevents leakage of extracellular fluid across a layer of epithelial cells

the plasma membranes of neighboring cells are very tightly pressed against each other, bound by specific proteins

Desmosomes

fasten cell membranes together into strong sheets

a type of anchoring junction

Gap junctions

provide cytoplasmic channels from one cell to an adjacent cell, allowing cells to communicate

also called communicating junctions

Plasma membrane fluidity

Unsaturated fatty acid tails prevent packing

Cholesterol reduces membrane fluidity at moderate temps but at low temps hinders solidification

Movement

all directions, all the time

Net movement

NEVER all directions all the time

Diffusion

Net movement that follows concentration gradient (high to low)

Cellular membranes

____________ are fluid mosaics of lipids and proteins

Passive transport

Net movement follows concentration gradient (simple + facilitated)

No energy is used

Simple diffusion

net movement follows concentration gradient

small and uncharged molecules (gases, steroids, H2O but difficult)

Facilitated diffusion

net movement follows concentration gradient

diffusion with help from protein channels or carriers (aquaporins)

ions, biomolecules, and H2O

Osmosis

diffusion of water molecules

[water] is hidden, so use [solute] to find net movement

Tonicity

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

Isotonic

What type of solution is this?

• same [solute]

• no net movement of water

Hypertonic

What type of solution is this?

• higher [solute]

• net movement of water out of the cell

Hypotonic

What type of solution is this?

• lower [solute]

• net movement of water into the cell

Active transport

uses energy to move solutes against their gradients

ex: Na+/K+ pump

Exocytosis

the cell secretes certain molecules by the fusion of vesicles with the plasma membrane

Endocytosis

the cell takes in molecules and particulate mater by forming new vesicles from the plasma membrane

First law of thermodynamics

the amount of energy in the universe is constant

Second law of thermodynamics

energy conversion increases the disorder (entropy) of the universe

Chemical energy

the potential energy available for release in a chemical reaction

Gibbs free energy

the portion of a system’s energy that can perform work when temperature and pressure are uniform throughout the system (G)

Exergonic reaction

G change is negative; reactants have more free energy

Breaking covalent bonds releases energy (chemical energy, heat, light)

catabolic reaction

Endergonic reaction

G is positive; products have more free energy

Forming covalent bonds stores chemical energy

Energy coupling

the use of an exergonic process to drive an endergonic one

Enzymes

speed up metabolic reactions by lowering energy barriers (activation energy)

reusable catalyst

Activation energy

the amount of energy needed to push the reactants to the top of an energy barrier

Substrate

describes reactant molecules that bind to the active site of an enzyme

Cofactors

a non-protein chemical compound that is required for an enzyme to function, a coenzyme

Competitive inhibitors

reduce the productivity of enzymes by blocking substrates from entering active sites

Noncompetitive inhibitors

impede enzymatic reactions by binding to another part of the enzyme cause it to change its shape

Feedback inhibition

a metabolic pathway is halted by the inhibitory binding of its end product to an enzyme that acts early in the pathway

Allosteric regulators

inhibit or activate enzymes with quaternary structure

bind to regulatory site and keep enzyme in a specific shape

Induced fit

substrate binding to active site causes temporary change in enzyme’s 3D shape

Adenosine triphosphate

what molecule is this?

• 3 phosphate groups

• 1 sugar ribose

• 1 nitrogenous base (adenine)

ATP hydrolysis

reaction of ATP and water that yields inorganic phosphate and ADP and releases energy (chemical and heat)

powers cell work

Cellular respiration

an aerobic (O2) and catabolic (breaking down glucose) pathway

Pathway

a series of chemical reactions giving the cell control over ATP yield

Cellular respiration equation

C6H12O6+6O2—>6CO2+6H2O+Energy(ATP, heat)

Redox Reaction

in cellular respiration:

glucose loses electrons (oxidized)

O2 gains electrons (reduced)

Nicotinamide adenine dinucleotide

NAD+ —> NADH

can carry 2 electrons

NADH function

delivers electrons to the mitochondrial electron support chain

Electron transport chain

series of molecules that pass electrons to O2, maintains proton gradient

built into the inner membrane of the mitochondria

Glycolysis

occurs in cytosol

break down glucose to extract electrons

some ATP synthesis (substrate level phosphorylation)

Pyruvate oxidation

occurs in mitochondrial matrix

produces acetyl coenzyme A

Citric acid cycle

occurs in mitochondrial matrix

starts with acetyl coenzyme A

extracts many more electrons

some ATP synthesis (substrate level phosphorylation)

Oxidative phosphorylation

involves mitochondrial inner membrane, matrix, intermembrane space

produced 90% total ATP

Energy investment phase

glucose split to form glyceraldehyde 3-phosphate

2 ATP used per glucose

part 1 of glycolysis

Energy payoff phase

In what phase does this occur?

glyceraldehyde 3-phosphate converted to pyruvate

per glucose: net 2 ATP, 2 NADH, H+, H2O, 2 pyruvate

Glycolysis products

per glucose:

• 2 pyruvate

• net 2 ATP

• H2O

• H+

• 2NADH

Pyruvate oxidation products

per glucose:

• 2 acetyl coenzyme A

• 2 NADH

• H+

• CO2

Flavin adenine dinucleotide

a coenzyme that acts as an electron carrier in cellular respiration

FAD+ —> FADH2

Citric acid cycle products

Per glucose:

• 6 NADH

• 2 FADH2

• 2 ATP

• 2 oxaloacetate

• H+

• CO2

Chemiosmosis

an energy-coupling mechanism that uses energy stored in the form of an H+ gradient across a membrane to drive cellular work.

NADH

What singular electron carrier yields 2.5 ATP?

FADH2

What singular electron carrier yields 1.5 ATP?

30 or 32

How much ATP is produced in total?

Oxidative phosphorylation products

Per glucose:

• 26 or 28 ATP

• H2O

Fermentation

anaerobic ATP production

1. glycolysis produces net 2 ATP, 2 NADH per glucose

2. NAD+ regeneration: NADH —> NAD+

Alcohol fermentation

pyruvate is converted to ethanol

Per glucose:

• net 2 ATP

• 2 NAD+

• 2 ethanol

• CO2

Lactic acid fermentation

pyruvate is reduced directly by NADH to form lactate as an end product

Per glucose:

• net 2 ATP

• 2 NAD+

• 2 lactic acid

Qualities of semi-permeable membrane

1. phospholipid bilayer

2. biomolecule mosaic

3. fluid mosaic bc of cholesterol and phospholipids