BIS2A: MT2 Lectures 10-12

Lectures 10-12

What is the cytoskeleton?

A network of protein polymers

What are the three main types of protein polymers?

• Microfilaments

• Intermediate filaments

• Microtubules

What are microfilaments and what are they made up of?

Made up of the protein strand actin; often interact with strands of other proteins.

What are intermediate filaments and what are they made up of?

• Made up of fibrous proteins organized into tough assemblages

  • Structural support

What are microtubules and what are they made up of?

• Long, follow cylinders made up of many tubulin molecules

• Contains alpha and beta tubulin

What are the functions of the cytoskeleton?

1. Maintaining/controlling cell shape

2. Controlling the internal organization of the cell

3. Force generation; transport of cellular payloads, movement of cell, cytokinesis

What are some characteristics of eukaryotic cells?

• Have nuclei, mitochondria, cytoskeletons, membrane-bound organelles such as the endoplasmic reticulum, golgi apparatus, lysosomes, and chloroplasts (plants)

What is the function of the nucleus?

Stores DNA and controls gene expression

What is the function of the mitochondria?

Generate ATP through aerobic respiration

What is the function of the endoplasmic reticulum?

Synthesizes proteins and lipids

What is the function of the golgi apparatus?

Modifies and packages proteins

What is the function of the lysosomes?

Break down macromolecules and cellular debris

What is the function of peroxisomes?

Detoxify harmful compounds

What is the plasma membrane and its purpose?

• Phospholipid bilar with embedded proteins that separate internal contents of the cell from its surrounding environment

• Controls passage of organic molecules, ions, water, and oxygen into and out of the cell

What are motor proteins and the main types?

• Move along the cytoskeleton transporting cargo

• Convert chemical energy from ATP into mechanical work

• Kinesins, myosins, and dyneins

What is the purpose of myosin?

• Move along actin filaments

• Muscle contraction, vehicle transport, cellular movement

What is the purpose of kinesins?

• Move along microtubules towards the positive end

• Nutrient transport

• Plays a role in mitosis

What is the purpose of dyneins?

• Move along microtubules towards the negative end

• Move towards cell center

• Retrograde transport

What does it mean if a compound is oxidized?

• It loses electrons

• Typically has a positive value (indicates loss of e-)

What does it mean if a compound is reduced?

• It has gained electrons

• Typically neutral or has a - symbol.

What is a reduced agent?

The one donating electrons, becoming oxidized in the process.

What is an oxidizing agent?

• The one accepting electrons, becoming reduced in the process

What does it mean if a compound has gained hydrogens?

• It gained electrons

• Reduced

What does it mean if a compound has lost hydrogens?

• Lost electrons

• Oxidized

What is electron affinity?

The ability of an atom or molecule to accept electrons

What does it mean for an atom to have a negative or positive electron affinity?

• Negative: Less tendency to accept electrons

• Positive: Greater tendency to accept electrons

What is redox/reduction potenial?

• The tendency of a molecule to gain or lose electrons in a reaction

What does a more positive or negative value in reduction potential indicate?

• Positive: Higher redox potential; stronger electron acceptor. Better oxidant

• Negative: Lower redox potential; stronger electron donor. Better reductant.

In a redox tower, which side of the reactions are oxidized and reduced? Are they electron donors or acceptors?

• Left side: oxidized. electron acceptor

• Right side: reduced. electron donor.

In relation to free energy, what does a large difference in delta E indicate?

Bigger change in delta G.

How do you calculate delta E?

E₀’ acceptor - E₀’ donor

What is the purpose of NAD+/NADH and FAD/FADH2?

• Electron carriers; facilitate electron transfer in metabolic pathways

• NAD+/NADH: key electron carriers in cellular respiration. NAD+ is oxidized; NADH is reduced

• FAD/FADH2: similar function in cellular respiration. FAD is oxidized; FADH2 is reduced

What are the key components of a NAD+ molecule?

• Dinucleotide; joined together by a phosphate bridge

• Contain sugar groups

• Two phosphate groups

• Can accept two electrons and a proton to become reduced into NADH.

What are the 3 phases of glycolysis?

1. Energy investment

2. Energy extraction

3. Energy recovery

What is ATP’s structure and purpose?

• Primary energy currency of the cell

• Structure: Composed of adenine (nitrogenous base), ribose (sugar), and three phosphate groups.

What is the hydrolysis of ATP reaction and what is it used for?

• ATP becomes ADP + Pi (inorganic phosphate)

• Releases energy; exergonic reaction

• Used to power cellular processes

What are endergonic reactions and how does the energy ratio differ?

• Require energy

• Product energy is greater than reactants

What are exergonic reactions and how does the energy ratio differ?

• Release energy

• Reactant energy is greater than products

Where are the phosphoanhydride bonds in ATP?

Between each phosphate. O-P bond.

What type of reaction is ATP hydrolysis?

• Exergonic

• High-energy due to phosphoanydride bonds breaking

What are three types of ATP phosphorylation and what do they all require/produce?

• Substrate level phosphorylation

• Oxidative phosphorylation

• Photophosphorylation

• Require ADP to produce ATP

What is substrate-level phosphorylation?

• Requires a phosphate from a substrate (molecule)

• Transferred directly to ADP to form ATP

What is oxidative phosphorylation?

• Result of redox being used to generate a proton gradient

• ATP synthesis via electron transport chain and ATP synthase

What is glycolysis and where does it take place?

• 10-step metabolic pathway that breaks down glucose into pyruvate, yielding ATP and NADH

• Takes place in cytoplasm

• Doesn’t require oxygen; anerobic process

What is the purpose of step 1 of glycolysis and its inputs/outputs?

• Phosphorylation.

• Input: Glucose + ATP

• Output: ADP + glucose-6-phosphate

• Traps glucose in the cell; prepares it for further breakdown

What is the purpose of step 3 of glycolysis and its inputs/outputs?

• Phosphorylation

• Inputs: Fructose-6-phosphate + ATP

• Output: ADP + fructose-1,6-biphosphate

• Commitment step; glycolysis must continue

What is the purpose of step 6 of glycolysis and its inputs/outputs?

• Redox reaction

• Input: Glyerceraldehyde-3-phosphate and NAD+ + Pi

• Output: 1,3-biphosphoglycerate and NADH + H+

• First redox reaction in glycolysis; produces NADH to be used for oxidative phosphorylation to make ATP

What is the purpose of step 7 of glycolysis and its inputs/outputs?

• Substrate-level phosphorylation

• Input: 1,3-diphosphoglycerate and ADP

• Output: 3-phosphoglycerate and ATP

• First ATP production; 2 ATP produced per glucose molecule

What is the purpose of step 10 of glycolysis and its inputs/outputs?

• Substrate-level phosphorylation

• Input: Phosphoenolpyruvate and ADP

• Output: Pyruvate and ATP

• Final ATP production; pyruvate can decide what metabolic pathway it wants to go down; highly regulated step

What are the two possible pathways pyruvate can go down based on its conditions?

• Citric acid cycle: In aerobic conditions; enters the mitochondria

• Fermentation: anaerobic conditions; lactate or ethanol production

What is the overall yield of glycolysis?

• 2 ATP

• 2 NADH (used in respiration)

• 2 Pyruvate