Zoology 100 Notes 2

ZOOLOGY 100 NOTES (2) Continuation.2 ---THE NUCLEUS OR BRAIN Nuclear structures: 1. Nucleoli - one or more where ribosomal RNA is synthesized 2. The nuclear envelope- a double membrane that surrounds the DNA and has pores that connect it with the cytoplasm 3. Chromatins 4. perinuclear cisternae ---CYTOPLASM OR CELL JELO Components: a. cytosol – semi-transparent fluid that suspends other elements of the cell b. Organelles c. inclusions ---CELLULAR METABOLISM CATABOLISM: breakdown molecules into smaller units; - it provides the chemical energy necessary for the maintenance of the living cell - EXAMPLES: a. breakdown of muscle proteins to use a.a. as substrates for gluconeogenesis b. breakdown of fat in adipose cells (fat-storage cells) to fatty acids. - Anaerobic Respiration: glucose broken down w/o oxygen; - w/o oxidative phorphorylation, NADH cannot be converted to ATP - when all the NAD+ molecules have been converted to NADH, glycolysis will stop unless NAD+ is generated by fermentation - Aerobic Respiration: glucose broken down w/ oxygen; 1. Pyruvate oxidation: 3-C pyruvate loses C & is shepherd into citric acid cycle by coenzyme A 2. Citric acid cycle/Kreb cycle: acetyl group from pyruvate enters this biochemical cycle & release carbon dioxide & water, & ATP, NADH, FADH2 3. Oxidative phosphorylation: NADH &FADH2 converted into usable ATP in the mitochondria by Electron transport chain

A simplified outline of the catabolism of proteins, carbohydrates and fats

Aerobic respiration (red arrows) is the main means by which both plants and animals utilize energy in the form of organic compounds that was previously created through photosynthesis (green arrow).

A few of the metabolic pathways in a cell ANABOLISM: builds larger molecules from smaller units; assembling tissues & organs; support: growth & differentiation in cells, increase in body size & repro. 1. Gluconeogenesis: de novo synthesis of glucose fm simple organic compound; a.a. in cellular protein to glucose 2. Glycogenesis: conversion of excess glucose into glycogen as a cellular storage mechanism; preventing osmotic pressure buildup in the cell

3. Glycogenolysis: breakdown of glycogen into glucose; providing glucose supply to glucose-dependent tissues 4. Photosynthesis (Carbon fixation): plant use to convert sun light, CO2 , & water into sugar; & producing ATP. ---METABOLISM AND ENERGY

---CELLULAR RESPIRATION

---TYPES OF CELULAR RESPIRATION

STEPS: 1. Prior to entering the Krebs Cycle, pyruvate must be converted into acetyl CoA (pronounced: acetyl coenzyme A). - achieved by removing a CO2 molecule from pyruvate and then removing an electron to reduce an NAD+ into NADH. An enzyme called coenzyme A is combined with the remaining acetyl to make acetyl CoA which is then fed into the Krebs Cycle. The steps in the Krebs Cycle are summarized below: 2. Citrate is formed when the acetyl group from acetyl CoA combines with oxaloacetate from the previous Krebs cycle.. 3. Citrate is converted into its isomer isocitrate.. 4. Isocitrate is oxidized to form the 5-carbon α-ketoglutarate. This step releases one molecule of CO2 and reduces NAD+ to NADH2+. 5. The α-ketoglutarate is oxidized to succinyl CoA, yielding CO2 and NADH2+. 6. Succinyl CoA releases coenzyme A and phosphorylates ADP into ATP. 7. Succinate is oxidized to fumarate, converting FAD to FADH2. 8. Fumarate is hydrolized to form malate.

9. Malate is oxidized to oxaloacetate, reducing NAD+ to NADH2+. BACK: at the beginning of the Krebs Cycle. Because glycolysis produces two pyruvate molecules from one glucose, each glucose is processes through the kreb cycle twice. For each molecule of glucose, six NADH2+, two FADH2, and two ATP. ---SYNTHESIS