Unit 2: Membranes, Energy, and Cell Communication

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Product Distribution -The Basics

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Subtopic

Integral Proteins

Cotransport Proteins

Active Transport Pumps

Carrier Protein

Channel Protein

Hydrophobic R groups

Peripheral Proteins

Hydrophilic R groups

Transport across Membranes

ATP Required

Endocytosis & Exocytosis

Active Transport

No ATP Required

Co-transport

Osmosis

Facilitated Diffusion

Diffusion

Unit 2: Membranes, Energy, and Cell Communication

Cell Signaling

Light reactions in photosynthesis

ATP production: chemiosmosis (protons pumped across thylakoid membrane, create sproteon gradient, drives ATP synthase)

e-: from H20, gives to NADP+

location: thylakoid membrane of chloroplast

e-: from NADH and FADH2, gives to O2

ATP production: chemiosmosis through ATP synthase

location: inner membrane space

ATP production in aerobic respiration

Chemiosmosis

Lots of ATP produced

proton gradient drives ATP synthase, ADP + Pi --> ATP

ETC

O2 combines with e- and protons to form water

H+ pumped into intermembrane space, creates proton gradient

e- go through protein complexes

NADH and FADH2 made from glycolysis and citirc acid cycle, give e- to ETC

Citric acid cycle

ATP generation: 2 ATP made through substrate level phosphorylation

Glycolysis

ATP usage: 2 ATP consumed in first 5 steps of glycolysis

ATP generation: 2 ATP made thourgh substrate level phosphorylation

Tyrosine Kinase receptor pathway

activated signaling proteins --> cascades --> gene expression

Phosphorylated tyrosines --> signaling proteins

activates kinase --> autophosphorylation of tyrosine

Ligand binds to dimer

GCPR receptor

Pathway

cAMP activates first kinase

Adynylyl cyclase converts ATP --> cAMP

Activated G protein activates adenylyl cyclase

GPT --> GTP and activates G protein

Ligand binds to GCPR receptor

Cell Energy

Cellular Respiration: ATP Production

ATP: The Energy Currency

ATP used in:

Chemical Work (Biosynthesis)

Transport Work (Active Transport)

Mechanical Work (Motor Proteins)

ATP Synthesis: ADP + Pᵢ → ATP (Requires energy)

ATP Hydrolysis: ATP → ADP + Pᵢ (Releases energy)

Photosynthesis: ATP & Energy Transfer

Comparison to Cellular Respiration

ATP is generated using a proton gradient in both mitochondria and chloroplasts.

Both processes use electron transport chains.

Calvin Cycle (Stroma)

ATP & NADPH used to fix CO₂ into glucose.

Light-Dependent Reactions (Thylakoid Membrane)

Electron transport & proton pumping to create ATP and NADPH.

Electron Transport Chain (ETC) & Chemiosmosis

ATP is generated by oxidative phosphorylation.

Proton (H⁺) gradient in the intermembrane space drives ATP Synthase.

Stages of Cellular Respiration

Oxidative Phosphorylation (ETC + Chemiosmosis) (Inner Mitochondrial Membrane)

Outputs: ATP (32-34), H₂O

Inputs: NADH, FADH₂, O₂

Citric Acid Cycle (Krebs Cycle) (Mitochondrial Matrix)

Outputs: ATP, NADH, FADH₂, CO₂

Inputs: Acetyl-CoA, NAD+, FAD

Pyruvate Oxidation (Mitochondrial Matrix)

Inputs: Pyruvate, NAD+

Outputs: Acetyl-CoA, NADH, CO₂

Glycolysis (Cytoplasm)

Inputs: Glucose, ATP, NAD+

Outputs: Pyruvate, ATP (net 2), NADH

Energy Transfer in Cells

Types of Metabolic Pathways

Anabolic Pathways ( Photosynthesis: synthesis of glucose using light energy)

Catabolic Pathways (Cellular Respiration: breakdown of glucose for ATP)

Laws of Thermodynamics

2nd Law: Energy transfer increases entropy.

1st Law: Energy is transferred and transformed, not created or destroyed.

Membranes

Factors Affecting Fluidity

Fatty Acid Composition (unsaturated vs saturated)

Temperature (higher = more fluid)

Cholesterol (maintains fluidity at various temperatures)

Functions of membranes

Signal Transduction

Selective Permeability

Structure of Membranes

Glycolipids

Cell recognition, stability & protection

Glycoproteins

Cell-cell recognition & signal reception

Phosplipid Bilayer

Maintains Flexibility

Phospholipids

Hydrophilic Head (phosphate group)

Hydrophobic Tails (fatty acids)