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Lecture Number 2

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Natural Science
NATS 1560
Richard Jarell

▯ SC/NATS 1560 3.00 ▯ Understanding ▯ Food ▯ Winter 2013 ▯ Prof Jarrell ▯ Day 2: ▯ Food in the Body ▯ CHAPTER 2 OVERVIEW ▯ The Cellular Basis of Life ▯ Cell Membranes ▯ Prokaryotic Cells ▯ Metabolic Processes ▯ Respiration and Energy ▯ Construction of Proteins ▯ Digestion: Mouth to the Intestines ▯ Digestion at the Molecular Level ▯ The Liver and Urinary System ▯ Hormones and Nutrition ▯ CELLULAR BASIS OF LIFE ▯ All life seems to be on the basis of the cell as its unit ▯ Biochemical activity is within/between cells ▯ Main division between prokaryotes and eukaryotes ▯ Eukaryotic cells have a lipid membrane around them ▯ CELLULAR STRUCTURE ▯ Membranes may be smooth or folded ▯ nutrients impermeable to alien substances, but will pass through water and ▯ Water moves across barrier by osmosis ▯ Tends to move from areas of low concentration of non-water molecules to one of high concentration ▯ Molecules moved around in cell/through membrane by active transport system ▯ CYTOPLASM ▯ Interior of cell is cytoplasm: fluid and various bodies ▯ Cell nucleus holds the primary genetic information of the cell ▯ Surrounded by a nuclear membrane with passages (annuli) ▯ Inside the nucleus is chromatin, unwound lengths of DNA ▯ CYTOPLASM ▯ Nucleolus is a unit where ribosomal RNA is manufactured ▯ Cytoplasm has many ribosomes, where proteins are constructed ▯ Other bodies are called organelles ▯ Endoplasmic reticulum: for storage and transport of proteins ▯ CYTOPLASM ▯ hormones and enzymes seems to be involved in production and transport of ▯ Mitochondria are the sites of respiration ▯ They have their own membranes and DNA ▯ CYTOPLASM II ▯ Plant and animal cells have vacuoles which store water and other molecules ▯ Lysosomes degrade large molecules into smaller ones ▯ Microtubules provide transport “monorails” ▯ CELL MEMBRANES ▯ Membranes concentrate chemicals for metabolism ▯ Protect inside of cell from invaders ▯ Move materials in and out of cell ▯ Operate as part of the inter-cellular signalling system ▯ CELL MEMBRANES ▯ Some membranes have protein-carbohydrate receptors embedded in them ▯ Cholesterol molecules keep membrane fluid and keep invaders out ▯ Glycocalyx (protein + carbohydrate) provides sticky outer surface ▯ MEMBRANE TRANSPORT ▯ Water and some molecules move by osmosis (lower to higher concentrations) ▯ Oxygen moves in by diffusion (higher to lower concentrations) ▯ Transport proteins: act like pipelines ▯ MEMBRANE TRANSPORT ▯ ATP-powered pumps (sodium-potassium pump) ▯ Larger-scale movement in and out ▯ Exocytosis: moves out ▯ Endocytosis: moves in ▯ PROKARYOTIC CELLS ▯ Prokaryotes (monera) include bacteria, cyanobacteria and mycoplasms ▯ Much smaller than eukaryotic cells ▯ Lack many of the organelles and internal structures ▯ DNA is not in a distinct nucleus ▯ DNA forms rings rather than strands ▯ They do have membranes, but also have a cell wall of polysaccharides ▯ Metabolism ▯ All the chemical activities in the body ▯ Mostly at the cellular level ▯ Catabolic processes: breaking down large molecules into smaller ones ▯ This releases energy ▯ Anabolic processes: building up larger molecules from smaller ones ▯ This requires energy ▯ Metabolism ▯ Dehydration synthesis – anabolic ▯ Removal of a water molecule between two adjacent molecules ▯ How polysaccharides are built up ▯ Also involved in building triglycerides and proteins ▯ Metabolism ▯ Hydrolysis adds water to break larger molecules into smaller units ▯ A catabolic process ▯ However, just adding water is too slow ▯ Require enzymes as catalysts ▯ In cells, we often see many steps to go from an initial substance to a final one ▯ Metabolic pathway ▯ Respiration ▯ We, like all animals, are heterotrophs ▯ Humans are holotrophs ▯ Other animals are saprotrophs or parasites ▯ Ultimate source of energy is the Sun, via photosynthetic plants ▯ Respiration ▯ Simple method of extracting energy is fermentation ▯ Typical of some fungi (yeasts) and bacteria ▯ C6H126▯▯▯▯2 5 OH + 2 CO ▯▯▯▯▯▯▯▯▯▯ ▯ Sugars break down into alcohol and carbon dioxide ▯ Releases a small amount of energy ▯ Respiration ▯ Respiration a way of extracting energy for aerobic organisms ▯ More complicated but extracts much more energy ▯ Glucose (or fats or proteins) broken down and oxidized ▯ This releases energy ▯ By-products are water and carbon dioxide ▯ Glycolysis ▯ First stage of respiration takes place in the cytoplasm ▯ It converts glucose, through several steps, into pyruvic acid ▯ Energy required to do this: uses ATP ▯ Adenosine triphosphate: 3 phosphate ions teamed with adenine + ribose sugar (from DNA) ▯ Krebs Cycle ▯ Pyruvate moves into the mitochondrion ▯ There follows the chain of reactions that make up the Krebs Cycle Produces 2 ATP 2lus CO ▯ ▯ Electron Transport Chain ▯ Electrons from the Kreb Cycle moved through Electron Transport Chain ▯ Oxidation takes place ▯ Final result: water ▯ Much more ATP comes from aerobic processes than from glycolysis ▯ Respiration can work using amino acids and glycerol ▯ Protein Construction ▯ Modern view of how genetic and protein-building machinery works ▯ DNA has the information for building proteins in th
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