bio 1 test 2

Phospholipids

• form the bilayer, capable of lateral movement but not flip-flopping between layers.

What is the main structure of the cell (plasma) membrane?

A phospholipid bilayer that is amphipathic (hydrophilic heads, hydrophobic tails).

What is the main function of the cell membrane?

Acts as a selectively permeable barrier, separating the internal cell environment from the external environment and maintaining homeostasis.

What does the fluid mosaic model describe?

The membrane as a dynamic mosaic of phospholipids, proteins, cholesterol, and carbohydrates.

Can phospholipids flip-flop between layers?

No, but they can move laterally within the bilayer.

What is the role of cholesterol in the membrane?

Regulates fluidity: prevents too much fluidity at high temps and solidification at low temps.

What is the role of carbohydrate chains on the membrane?

Cell recognition, immune response, and protection (via glycoproteins and glycolipids).

What are the main types of membrane proteins and their functions?

• Transport proteins → move substances across membrane

• Receptors → detect signals like hormones

• Enzymes → catalyze reactions

• Structural proteins → provide support and shape

Which molecules diffuse freely across the membrane?

Small, nonpolar molecules (e.g., O₂, CO₂).

Which molecules require transport proteins?

Large, polar, or charged molecules (e.g., glucose, ions).

What drives passive transport?

Concentration gradients (high → low concentration).

What are the three types of passive transport?

Simple diffusion, facilitated diffusion, and osmosis.

What is osmosis?

Diffusion of water from hypotonic (low solute) to hypertonic (high solute) solutions.

Effect of hypotonic solution on animal cells?

Swelling, possible lysis.

Effect of hypertonic solution on plant cells?

Plasmolysis (membrane pulls away from wall).

How does active transport differ from passive transport?

Active transport requires energy (ATP or gradients) and moves substances against their concentration gradient.

Example of active transport in cells?

Na⁺/K⁺ ATPase pump (important for nerve impulses).

What are the two main types of bulk transport?

• Exocytosis: exports molecules (e.g., hormones).

• Endocytosis: imports molecules (phagocytosis, pinocytosis, receptor-mediated).

What are the main forms of energy in cells?

Kinetic, potential, and chemical (stored in bonds).

What are exergonic vs endergonic reactions?

• Exergonic: release energy, spontaneous.

• Endergonic: require energy, non-spontaneous.

What are catabolic reactions?

Breakdown reactions that release energy (exergonic).

What are anabolic reactions?

Building reactions that require energy (endergonic).

What is the main function of enzymes?

Speed up reactions by lowering activation energy without being consumed.

What is the induced fit model?

Enzymes change shape slightly to fit substrates better.

What is the transition state?

High-energy, unstable state during a reaction; enzymes stabilize it.

What are cofactors?

Inorganic helpers (e.g., metal ions).

What are coenzymes?

Organic helpers (e.g., vitamins).

What are prosthetic groups?

Tightly bound non-protein molecules essential for enzyme activity.

What factors affect enzyme activity?

Substrate concentration, pH, temperature, inhibitors.

What are competitive inhibitors?

Bind to the active site and block substrates.

What are non-competitive inhibitors?

Bind to allosteric sites, changing enzyme shape.

What’s the difference between reversible and irreversible inhibitors?

Reversible bind temporarily; irreversible form permanent covalent bonds.

Why do organisms require energy?

To sustain life processes like growth, repair, reproduction, muscle contraction, nerve impulses, and metabolism.

What is the primary usable energy form in cells?

ATP (adenosine triphosphate).

What percentage of energy goes to basal metabolic functions?

60–75%

What percentage goes to lifestyle activities?

20–35%

What percentage goes to digestion of food?

5–10%

What is the overall reaction for aerobic respiration?

Glucose + Oxygen → Carbon dioxide + Water + ATP

What are the byproducts of aerobic respiration?

CO₂, H₂O, and heat

Why is aerobic respiration efficient?

It yields ~30–32 ATP per glucose molecule

Why is ATP useful for cells?

It releases energy when phosphate bonds break and can be quickly regenerated

Where is most ATP produced?

In mitochondria (“energy factories” of the cell)

What happens during oxidation?

Loss of electrons

What happens during reduction?

Gain of electrons

In respiration, what is oxidized and what is reduced?

Glucose is oxidized, oxygen is reduced

What is the oxidized form of NAD+ and its reduced form?

NAD+ → NADH

What is the oxidized form of FAD and its reduced form?

FAD → FADH₂

What is the role of NADH and FADH₂?

Carry high-energy electrons to the electron transport chain

Where does glycolysis occur and what does it produce?

Cytosol; 2 pyruvate, 2 ATP (net), 2 NADH

What happens during pyruvate conversion?

Pyruvate → Acetyl CoA + CO₂ + NADH

What does the Citric Acid Cycle produce per Acetyl CoA?

2 CO₂, 1 ATP, 3 NADH, 1 FADH₂

Where does oxidative phosphorylation occur and what is its main function?

Inner mitochondrial membrane; produces ATP using ETC and chemiosmosis

What drives ATP synthase?

Proton (H⁺) gradient across the inner mitochondrial membrane

How many ATP per NADH?

~3 ATP

How many ATP per FADH₂?

~2 ATP

Why does fermentation occur?

To regenerate NAD+ so glycolysis can continue without oxygen

What are the two types of fermentation?

Lactic acid (humans, some bacteria) → lactate + 2 ATP.
Alcoholic (yeast, some bacteria) → ethanol + CO₂ + 2 ATP.

What alternative electron acceptors are used in anaerobic respiration?

Nitrate (NO₃⁻), sulfate, or carbon dioxide

How do proteins contribute to respiration?

Amino acids are deaminated and enter glycolysis or Krebs cycle

How do fats contribute?

Fatty acids undergo beta-oxidation → Acetyl CoA (very energy-dense).

Aerobic respiration: Products, ATP yield, oxygen requirement?

H₂O + CO₂, high ATP yield, requires oxygen.

Fermentation: Products, ATP yield, oxygen requirement?

Lactate or ethanol + CO₂, low ATP yield, no oxygen.

Anaerobic respiration: Products, ATP yield, oxygen requirement?

Variable products, moderate-to-large ATP yield, no oxygen (alternative acceptors)

The process by which cells take in substances from outside of the cell by engulfing them in a vesicle is termed

endocytosis

exocytosis

The packaging of materials into vesicles and their excretion from the cell occurs during the process of