Biology Membrane Structure and Transport

Study Notes

Membrane Structure and Transport

Membranes are composed of a fluid mosaic model, where proteins are embedded in a lipid bilayer
Lipids move laterally in the membrane
Plasma membrane components include a phospholipid bilayer, protein network, cell surface markers, and transmembrane proteins.
Cell membranes form so hydrophobic tails do not touch water.

Passive Transport

Passive transport does not require energy
Simple diffusion involves movement along a concentration gradient, no proteins needed
Facilitated diffusion uses transport or channel proteins for movement across the plasma membrane
Osmosis is the spontaneous movement of water across a membrane, often requiring aquaporins

Active Transport

Active transport requires energy
Solute pumps use proteins to move substances against a concentration gradient, requiring transport proteins
Bulk transport moves large molecules or quantities using exocytosis and endocytosis.

Exergonic & Endergonic Reactions

Exergonic reactions release energy, Gibbs free energy is negative
Endergonic reactions absorb energy, Gibbs free energy is positive
The first law of thermodynamics states that energy cannot be created or destroyed
The second law of thermodynamics discusses entropy, the tendency toward disorder.

Enzymes

Enzymes are protein catalysts produced by living organisms, lowering activation energy for reactions.
Enzymes have an active site where a substrate binds
Allosteric sites are "off switches" for enzyme function
Competitive inhibitors compete with the substrate for the active site
Noncompetitive inhibitors bind to allosteric sites
Cofactors are inorganic molecules that help enzymes function
Biochemical pathways are sequences of reactions where product becomes substrate for next reaction
Advantages of multienzyme systems is that the reactant products can be contained in the same area.
Feedback inhibition occurs when a product inhibits an early enzyme in a pathway

Cellular Respiration

Cellular Respiration purpose is to make ATP, using glucose and oxygen to produce ATP
Four steps of Aerobic Cellular Respiration are: Glycolysis, Pyruvate Oxidation, Krebs Cycle, Electron Transport Chain

Glycolysis

This is the first step of the pathway

Pyruvate Oxidation

Pyruvate is oxidized, generating NADH and Acetyl-CoA
Reactants: 2 Pyruvate, NAD+, 2 CoA
Products: 2 Acetyl-CoA, 2 NADH, 2 CO2

Krebs Cycle (Citric Acid Cycle)

Acetyl-CoA generates ATP, NADH, and FADH2
Reactants: 2 Acetyl-CoA, 6 NAD+, 2 FAD, 2 ADP, 2 Oxaloacetate
Products: 6 NADH, 2 FADH2, 2 ATP, 4 CO2

Electron Transport Chain (ETC)

NADH and FADH2 from previous steps donate electrons, creating a proton gradient
Reactions generate ATP through ATP synthase
Reactants: 2 FADH2, 10 NADH, O2
Products: 34 ATP, H2O
Overall Cellular Respiration Reaction: 6O2 + C6H12O6 → 6CO2 + 6H2O + 38 ATP

Fermentation

Anaerobic respiration utilizes inorganic molecules for electron transport when oxygen is not available
Fermentation types include ethanol and lactic acid fermentations.

Photosynthesis

Photosynthesis uses sunlight to create glucose from CO2 and H2O
Two major stages are Light-Dependent Reactions and Calvin Cycle

Light-Dependent Reactions

Calvin Cycle

CO2 is fixed, reducing PGA into G3P
Three cycles make enough carbon for 1 G3P, 6 cycles make a glucose molecule.
Reactants: CO2, ATP, NADPH
Products: Glucose
Overall Photosynthesis Reaction: 6CO2 + 12H2O → C6H12O6 + 6O2 + 6H2O

Photorespiration

C3 plants suffer photorespiration.
C4 and CAM pathways can minimize photorespiration.
C3 is energy efficient, C4 and CAM require more energy and have slower growth.
C4 plants separate initial CO2 fixation and Calvin Cycle in different cells.
CAM plants separate these steps by time (day/night)

Comparing Respiration & Photosynthesis

Similarities: Share products and reactants, ETC, ATP synthase, proton gradient
Differences: location(mitochondria vs chloroplast), organisms require respiration (animals), photosynthesis needed for plant growth.

Description

Explore the concepts of membrane structure, transport mechanisms, and energy dynamics in this quiz. Test your understanding of passive and active transport, and how cell membranes function. Ideal for students studying cell biology or related fields.

Biology Membrane Structure and Transport

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Questions and Answers

What is the main purpose of cellular respiration?

Which of the following accurately describes a characteristic of endergonic reactions?

During facilitated diffusion, which component is primarily required?

What is the role of NAD+ during pyruvate oxidation?

Which enzyme catalyzes the fixation of carbon during the Calvin Cycle?

What consequence does the presence of competitive inhibitors have on enzyme activity?

Which of the following is NOT a step in aerobic cellular respiration?

What is the role of coenzymes in enzyme activity?

What is the end product of the Krebs Cycle from two Acetyl-CoA molecules?

Which type of transport involves moving molecules against their concentration gradient?

How do CAM plants minimize water loss during photosynthesis?

What function does ATP synthase serve in cellular respiration?

What distinguishes the C4 pathway from C3 in plants?

In what way do exergonic reactions differ from endergonic reactions?