Lecture_11_Cell Energy II

Cellular Energy II (Ch. 13)

General Features of Carbohydrates: Describe their structure and functions.
Monosaccharides: Recognize the names and general structural features.
Cellular Respiration: Understand the general formula and detailed features of its three stages:
- 1) Glycolysis: Conversion of glucose to pyruvate.
- 2) Citric Acid Cycle: Processing of acetyl-CoA.
- 3) Respiratory Electron Transport Chain: Energy production and electron carrier regeneration.
Fates of Pyruvate: Role of oxygen availability.
Respiration & Carbon Skeletons: Associated production processes.
Regulation of Glycolysis: Mechanisms of feedback regulation.
Food Storage in Cells: Mechanisms of how cells store food molecules.

Abundance: Carbohydrates are the most abundant biomolecules on Earth, comprising sugars and saccharides.
Structure: Carbon compounds containing many hydroxyl groups. Commonly end in –ose.
Features:
- Chiral centers: Carbon atoms with four different groups.
- Examples of size range: From glyceraldehyde (3C) to amylopectin (>200,000,000 g/mol).
Glycosidic Bonds: Covalent linkage of sugars with each other or with proteins/lipids.

Energy Storage: Storage forms include glucose, glycogen, and starch.
Biological Roles:
- Building blocks for complex carbohydrates, RNA, DNA, vitamins (e.g., L-ascorbic acid), and amino sugars (e.g., glucosamine).
- Molecular recognition for the immune system.
- Structural roles in cellular protection (plant and bacterial cell walls).
- Cell adhesion through glycoproteins.
- Biological lubrication and maintenance of structure (e.g., cellulose and chitin).

Sources: Common sugars include fructose, sucrose, lactose, starch, and cellulose (dietary fiber).
Links: Online resources for further exploration of sugars and starch.

Definition: Cannot be hydrolyzed into simpler carbohydrates.
Types: Include:
- Trioses (3C), tetroses (4C), pentoses (5C), hexoses (6C), heptoses (7C).
Isomers: Molecules with the same formula but different structures; Question example: identifying ketoses.

Process Overview: Oxidation of food molecules provides energy and carbon skeletons for biosynthesis.
Energy Release: Controlled release during three stages prevents cell damage.
- Stages:
  - Glycolysis
  - Tricarboxylic Acid Cycle (TCA)
  - Respiratory Electron Transport Chain
Reaction Efficiency: ΔGo’ = -2880 kJ/mol; efficient energy conversion from food substrates.

Digestion Stage: Outside cell; conversion of large molecules.
Glycolysis & Pyruvate Oxidation: Starts in the cytosol and ends in the mitochondrial matrix; production of ATP and NADH.
Citric Acid Cycle & Oxidative Phosphorylation: Occurs in mitochondria; significant ATP production from NADH in the electron transport chain.

Energy Investment Phase: First steps include phosphorylation of glucose, isomerization, and further phosphorylation controlled by phosphofructokinase.
Energy Generation Phase: Conversion of glyceraldehyde 3-phosphate leading to ATP generation and NADH production.
Irreversible Steps Identified: Steps 1, 3, and 10 are irreversible in glycolysis.

Dependence on Oxygen: Pyruvate enters respiration or fermentation based on oxygen levels.
- Fermentation Types:
  - Alcoholic: Yeast produces ethanol and CO2.
  - Lactic Acid: Muscle cells produce lactate.
Function: Both fermentation types regenerate NAD+ for glycolysis continuity.

Sources: Formed from pyruvate in aerobic metabolism and fatty acid breakdown via β-oxidation.
Enzyme Complex: Pyruvate dehydrogenase complex facilitates conversion to acetyl-CoA.

Functionality: Acetyl-CoA oxidation to CO2; generates NADH and FADH2, crucial for energy production.
Localization: Most enzymes reside in the mitochondrial matrix except for succinate dehydrogenase, which interacts with the electron transport chain.
Energy Yield from One Hexose Molecule: Breakdown through glycolysis, TCA, and ATP production.

Mechanism: Activated carriers (NADH & FADH2) donate electrons to the electron transport chain, establishing a proton gradient that drives ATP synthesis. True or False: Oxidative phosphorylation requires a proton gradient.

Caloric Pathways: Catabolic pathways deliver substrates to glycolysis and TCA for energy, while anabolic pathways utilize the products for biosynthesis.
Feedback Regulation Mechanisms: Involve glucose levels impacting glycolytic and gluconeogenesis pathways.

Glycogen and Starch: Animal cells utilize glycogen while plant cells utilize starch for glucose storage.
Fat Storage: Stored as triacylglycerols in adipocytes for animals and in seeds for plants.
Importance: Stored carbohydrates and fats are primary nutrient sources for animals, including humans.