Bio Test 3

What is the structure and function of the plasma membrane?

Structure: The plasma membrane consists of phospholipids (hydrophilic heads, hydrophobic tails, integral proteins, and cholesterol (Animal Cells)

Function: Regulates the movement of substances in and out of the cell, maintaining a steady internal environment

• Cholesterol maintains structural integrity and fluidity of membrane

Label the following diagram of the plasma membrane

What are integral proteins?

Integral proteins are membrane proteins that span the entire lipid bilayer and play roles in transport, acting either passively or actively.

What are the 5 types of Integral Proteins?

1. Channel Proteins

2. Carrier Proteins

3. Receptor Proteins

4. Enzymatic Proteins

5. Cell-Recognition Proteins

• Also known as Major Histocompatibility Complex (MHC) Glycoproteins

What are the functions of the 5 Integral Proteins?

1. Channel Protein:

• Simple Diffusion (Transport)

2. Carrier Protein:

• Facilitated Transport

• Active Transport

3. Receptor Protein:

• Cell Signaling

  • Uses “lock and key method”

  • Correct key “unlocks” cell and causes a reaction to occur

4. Enzymatic Protein:

• Catalyze (speeds up) a specific reaction

• Acts as an enzyme that synthesizes or breaks down certain molecules

• Involved in metabolism

5. Cell Recognition Protein:

• Identifies whether cell is “self” or “non-self” (foreign)

  • If foreign, an immune response is triggered

Which Integral Proteins function passively (no ATP) or actively (ATP required)?

1. Channel Protein: Passive

2. Carrier Protein:

• Passive: Facilitated Transport

• Active: Active Transport

3. Receptor Protein: Active

4. Enzymatic Protein: Active

5. Cell-Recognition Protein: Active

Provide an example of the function of each Integral Protein in the body

1. Channel Protein

• Aquaporin: used in osmosis (diffusion of water)

2. Carrier Protein:

• Facilitated Passive Transport: Chloride Channels

  • Movement of Chloride ions across lung cells resulting in watery mucus and reduced bacterial infection

• Active Transport: Sodium/Potassium (Na⁺/K⁺) Pump

  • Nerve Simulation relies on the movement of Na+ and K+ using the pump

3. Receptor Protein:

• Insulin Receptor: unlock glucose channel, allowing glucose to enter the cell

4. Enzymatic Protein:

• Involved in metabolism (ex: Lactase and lactose)

5. Cell-Recognition Protein

• Blood Type (antigens identify Blood Type; A-antigen, B-antigen)

What is the ratio of the Sodium : Potassium (Na⁺ : K⁺) ion movement and in which direction?

3 Sodium Ions (Na⁺) out

2 Potassium Ions (K⁺) in

Does the Sodium/Potassium (Na⁺/K⁺) Pump require ATP? If so, how many ATP per 1 cycle?

Requires 1 ATP per cycle

What is osmosis?

Osmosis is the movement of water across a semipermeable membrane from an area of lower solute concentration to an area of higher solute concentration.

Describe the 3 different extracellular environments:

• Isotonic, Hypotonic, Hypertonic

Isotonic: Solute concentration is equal inside and outside the cell

Hypotonic: Solution has a lower solute concentration outside the cell

• Ex. More H₂O outside of the cell

Hypertonic: Solution has a higher solute concentration outside the cell

• Ex. Less H₂O outside of the cell

How does each of the extracellular environments affect Red Blood Cells (RBCs)?

Isotonic: equal H₂O moves inside and outside the cell

Hypotonic: less solute concentration outside the cell (more H₂O outside)

• H₂O moves from High (out) to Low (inside), swelling the cell and causing it to burst (lysis)

Hypertonic: high solute concentration outside the cell (less H₂O outside)

• H₂O moves from High (inside) to Low (outside), shrinking (crenation) the cell

Define exocytosis.

Exocytosis is the process by which cells expel materials, increasing cell surface area and decreasing volume.

Define endocytosis.

Endocytosis is the process by which cells take in materials, decreasing cell surface area and increasing volume.

What are the three types of endocytosis? Provide a human example for each

1. Phagocytosis (cell eating)

• Ex: Phagocytes (White Blood Cells) engulf invading bacteria

2. Pinocytosis (cell drinking)

• Ex: Red Blood Cells take in iron content using pinocytosis

3. Receptor-mediated endocytosis.

• Selective endocytosis as substances brought into the cell bind to receptors

• Ex: Nutrients from maternal blood into fetal blood at the placenta

What is energy?

Energy is the capacity to do work

1. Potential (stored) energy; stored for later

• Ex. chemical bonds → chemical energy

2. Kinetic energy; comes from movement

• Ex. ball rolling down a hill

What are the two laws of thermodynamics?

1. Energy cannot be created or destroyed; can only be converted from one form to another

2. Energy cannot be converted from one form to another without a loss of usable energy

Define Entropy

Measurement of the amount of randomness in a physical/biological system

• Relative amount of randomness

From the diagrams shown, describe the levels of potential energy and entropy (which has more or less)

Diagram 1 (left)

• more potential energy

• less entropy (randomness/chaos)

Diagram 2 (right)

• less potential energy

• more entropy (randomness/chaos)

What is ATP cycling?

ATP cycling refers to the conversion of ATP to ADP (adenosine diphosphate) and back, releasing and storing energy in the process.

Define Exergonic and Endergonic reactions

Exergonic:

• Energy is released to surrounding environment

• Exothermic (Heat released, increases temp)

• Entropy is increased

Endergonic:

• Requires input of energy

• Endothermic (Heat absorbed, decreases temp)

• Entropy is decreased

How does ATP cycling relate to Endergonic and Exergonic reactions?

Endergonic Reaction:

• Cellular Respiration in Mitochondria

  • ADP + P + (energy of input) → ATP

Exergonic Reaction:

• Hydrolysis of ATP

  • ATP (release of energy) → ADP + P

Coupled Reactions: Energy released by an exergonic reaction is used to drive an endergonic reaction

What is the difference between anabolism and catabolism? What about metabolism?

Anabolism:

• Metabolic process that builds molecules from smaller molecules

Catabolism:

• Metabolic process that breaks down molecules into smaller molecules and energy

Metabolism:

• Sum of all anabolic and catabolic processes

What type of macromolecule is an enzyme?

Protein

What is the function of enzymes?

Enzymes catalyze (speed up) chemical reactions by lowering the Energy of Activation (E_a) required.

How are enzymes named?

Named by their substrate and end with “ase”

Label the following diagrams

What is the active site of an enzyme?

The active site is the region on an enzyme where substrate molecules bind and undergo a chemical reaction.

What is a Metabolic Pathway?

A series of linked reactions that create a product from reactants with the help of enzymes

• Products become reactants in the following “reaction” until the end product

Which of the lables are Reactants? Products? Enzymes?

Reactants (Substrates): A to C

Products: B to D

Enzymes: E1 to E3

Which graph depicts an endergonic reaction? An exergonic reaction?

Describe the Induced Fit Model for enzymes

Active site of the enzyme undergoes a slight change in shape to allow substrate to bind

• The change in shape facilitates reaction by achieving optimum fit

What are different factors affecting Enzymatic Speed?

1. Enzyme and Substrate Concentration

2. Environmental Factors (temperature and pH)

3. Cofactors and Coenzymes

4. Enzyme Inhibitors and Activators

How does Enzyme and Substrate Concentration affect Enzymatic Speed?

Enzyme Concentration:

• Increasing Enzyme Concentration → Rate of reaction increases

Substrate Concentration:

• Enzyme activity increases as Substrate Concentration increases

• Maximum rate is achieved when all the active sites of an enzyme are filled (point of saturation)

  • Increasing Substrate Concentration no longer affects reaction rate

How do Environental Factors (temperature and pH) affect Enzymatic Speed?

Each enzyme has an optimal temperature and pH in which it can function

• Wrong temperature/pH can denature the protein, changing its shape and function

How do Cofactors and Coenzymes affect Enzymatic Speed?

Cofactors:

• Molecules that help enzymes function

• Inorganic (no Carbon or Hydrogen) cofactors bind to another site on the enzyme that open up the active site to allow binding of substrates

Coenzymes:

• Organic non-protein cofactors that bind to the active site of the enzyme

  • activates the enzyme to start catalyzing a reaction

How do Enzyme Inhibitors affect Enzymatic Speed?

Two types:

1. Competitive Inhibitors

• Bind to active site on enzyme, competing with the substrate

2. Non-Competitive Inhibitors (also called allosteric regulation)

• Bind to another part of an enzyme, causing the enzyme to change shape and make the active site less effective

How do Enzyme Activators affect Enzymatic Speed?

Some enzymes take a long time to activate and aren’t needed all the time

• can be turn on/off to regulate enzyme concentration

Inactive enzymes can be activated:

• Adding/removing phosphates

• Cleaving (removing) part of the enzyme to reveal active site

• Associating with protein or cofactor

  • Opens up active site

What is cellular respiration? Does it occur in animal, plant cells or both?

Process by which cells convert glucose and oxygen into energy (ATP), carbon dioxide, and water.

What is the overall reaction of cellular respiration?

C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + 36-38 ATP

What are the steps of cellular respiration?

1. Glycolysis

2. Pyruvate Oxidation (Prepatory/Prep Reaction)

3. Krebs (Citric Acid) Cycle

4. Oxidative Phosphorylation/Electron Transport Chain (ETC)

Label the following diagram of the Mitochondria

What is an Oxidation Reaction? A Reduction Reaction?

Oxidation:

• Loss of electrons and hydrogen (O_xidation I_s L_oss)

• Gain of Oxygen

Reduction:

• Gain of electrons and hydrogen (R_eduction I_s G_ain)

• Loss of Oxygen

What are the inputs and outputs of Glycolysis? Where does it take place?

Inputs:

1. 1 (6C) Glucose

2. 2 NAD⁺

3. 2 ATP

4. 4ADP + 2AP

Outputs:

1. 2 (3C) Pyruvate

2. 2 NADH

3. 2 ADP

4. 4 ATP Total

• 2 ATP net gain

Location: Takes place in the cytosol

What are the inputs and outputs of Pyruvate Oxidation (Prep Reaction)? Where does it take place?

Reaction occurs twice per 1 glucose molecule

Inputs:

1. 2 Pyruvate

2. 2 CoA (Coenzyme A)

3. 2 NAD⁺ (Redox Reaction)

Outputs:

1. 2 Acetyl CoA

2. 2 CO₂

3. 2 NADH + H⁺ (NAD+ reduced + oxidized to NADH + H⁺)

Location: Matrix of the Mitochondria

What are the inputs and outputs of Krebs (Citric Acid) Cycle? Where does it take place?

Reaction occurs twice per 1 glucose molecule

Inputs:

1. 2 Acetyl Groups

2. 6 NAD⁺

3. 2 FAD

4. 2 ADP + 2 P

Outputs:

1. 4 CO₂

2. 6 NADH + H⁺

3. 2 FADH₂

4. 2 ATP

Location: Matrix of the Mitochondria

What are the inputs and outputs of Oxidative Phosphorylation (Electron Transport Chain (ETC))? Where does it take place?

Reaction occurs twice per 1 glucose molecule

Inputs:

1. 10 NADH + H⁺

2. 2 FADH₂

3. 6 O₂

Outputs:

1. 32 - 34 ATP

2. 6 H₂O

Location: Cristae of the Mitochondria

Summarize what happens during Oxidative Phosphorylation (Electron Transport Chain)

Analogy: Baton Pass Race

• Electrons from NADH and FADH₂ are passed down the chain along electron carrier proteins, 2 at a time

  • Analogy: electron carrier protein passes electrons to next protein; Runner passes baton to the next runner

• NADH and FADH₂ are oxidized, making the next protein complex reduced

  • Analogy: NADH and FADH₂ lose electrons, protein complex gains electrons; Runner no longer loses baton, next runner (protein) gains baton

• As electrons move down the chain, the energy released allows H⁺ ions to move into the intermembrane space

• O₂ removes electrons from the last electron carrier protein (protein IV) and combines with H⁺ to form H₂O

  • Analogy: O₂ gains electrons + H⁺ , forming H₂O; Last runner gains baton and finishes the race, drinking water to hydrate

What is substrate-level phosphorylation? How does it differ from Oxidative Phosphorylation?

Substrate-level phosphorylation: direct transfer of a phosphate group to ADP to form ATP during glycolysis and the Krebs cycle.

Oxidative Phosphorylation: ATP is formed from chemiosmosis

• The process of moving H⁺ to the other side of a membrane results in a gradient

• As H⁺ passes through the membrane, energy is captured to form ATP

What is the ATP yield for NADH and FADH₂ in the ETC?

NADH: 3 ATP

FADH₂: 2 ATP

How many ATPs are produced from one glucose molecule in each step of cellular respiration?

Glycolysis: 2 ATP

Pyruvate Oxidation (Prep Reaction): 0 ATP

Krebs (Citric Acid) Cycle: 2 ATP

Oxidative Phosphorylation (Electron Transport Chain): 32-34 ATP

Total: 36-38 ATP