Module 1: Molecular Cell Biology

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Prokaryotes
-What they include
-Unique features

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-the bacteria and blue green algae
-comparatively simple organisms and contain only the plasma membrane and no other membrane-bound organelles. Their DNA molecule is usually a single, circular chromosome.

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Eukaryotes
-Comparison
-Unique features

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-Extremely complex and highly organized.
-The major organelle is the nucleus, bounded by a double membrane and containing multiple, linear chromosomes. The cytoplasm contains additional membrane-bounded organelles. These include the mitochondria, the Golgi apparatus, the lysosome, the endoplasmic reticulum (ER), and, in plants, the chloroplast. Mitochondria and chloroplasts are bounded by double membranes and contain their own genetic material. Chloroplasts are the organelles that take light energy and use it to synthesize carbohydrates. Mitochondria are involved in the utilization of carbohydrates for the production of adenosine triphosphate (ATP) during aerobic respiration.

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Cell or Plasma Membrane

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a semipermeable living layer of the cell protoplasm. Serves protective and structural functions.

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Cell Wall

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a rigid non-living permeable barrier surrounding the Cell or Plasma Membrane

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Cytoplasm

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A complex of organic and inorganic substances external to the nuclear area including the cytosol (fluid portion) and organelles and membranes

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Inclusion bodies

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insoluble aggregates of proteins and other materials are stored here.

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Mesosome

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a membranous structure associated with DNA synthesis and secretion of proteins

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Nuclear region

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non-bounded area containing DNA for replication.

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Ribosomes

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sites of protein synthesis. free-floating in cytoplasm.

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Chloroplast

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in plants, the site of photosynthesis

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Chromatin (Chromosomes; DNA)

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The molecules in the Nucleus where cells store their hereditary information

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Centriole

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function in cell division, forming the spindle apparatus.

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Smooth ER

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A tubular structure which detoxifies poisons and synthesizes lipid

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Rough ER

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Contains Ribosomes and is involved in protein synthesis

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Golgi Apparatus

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This (along with the Endoplasmic Reticulum) is involved in the synthesis of membrane and secreted proteins.

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Lysosome

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This is a digestion chamber

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Microfilaments

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These are also a part of the cytoskeleton

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Microtubules

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Part of the cytoskeleton that criss-crosses the cytoplasm and forms a system of girders, ropes and motors that give the cell mechanical strength, controls the cell’s shape and drive and guide cellular movement

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Nuclear Envelope

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This is the membrane which separates the DNA from the cytoplasm

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Nucleolus

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Site of ribosome synthesis

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Nucleus

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contains the chromatin, or DNA.

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Mitochondria

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Small bodies in the cytoplasm of the cell take up oxygen and harness energy from the oxidation of food molecules to produce most of the ATP that powers the cell’s activities

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Vesicles

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involved in the secretion and transport of materials in the cell

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Structure/function of proteins

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Proteins form all enzymes and many structural components of the cell, such as the cytoskeleton and as part of membranes. If the cell is a machine, the proteins act as the structural support system and all the moving parts. They are composed of amino acids.

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Structure/function of carbohydrates

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-Simple Sugars (monomers and dimers) are for energy production
-Complex Carbohydrates are storage forms of simple sugars, to be released when needed.

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Structure/function of lipids

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-Fatty Acids, which play the role of storing energy and also form the principal component of membranes
-Steroids form many hormones including the sex hormones and cholesterol.

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Structure/function of nucleic acids

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-DNA (Deoxyribonucleic Acid) which is a double-stranded molecule and constitutes the chromosomes
-RNA, (Ribonucleic Acid), which is single stranded and plays the role of an intermediary for decoding the information in the DNA and transferring it to proteins.

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Structure/formation of ATP

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-o ATP (see Fig. 2-26, p. 61 of the Alberts et al. textbook for structures) is a small molecule that stores readily available chemical energy in two phosphoric anhydride bonds.
-Plants, bacteria, and animal cells break down food molecules to make ATP. Plants can form ATP via photosynthesis (photophosphorylation).

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Use in anabolism vs. catabolism

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-phosphates added to (AMP or ADP) to form ATP to be stored or used at a later time in catabolism. I.e. protein synthesis or photosynthesis.
-ATP loses Phosphates (becoming ADP or AMP) to be used to supply energy in bodily processes. i.e. cellular respiration or digestion.

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Evolutionary significance of ATP

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The significance of ATP in regards to evolution is that its adenine-ribose-phosphate combination is present in numerous other molecules that are essential to cell survival, such as: NAD, FAD, NADP, Acetyl CoA, RNA and DNA.

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ER

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o Only proteins that carry a special Endoplasmic Reticulum (ER) signal sequence are imported into the ER from the cytosol. The signal sequence is recognized by a signal recognition particle (SRP), which directs these proteins to a receptor protein on the surface of the ER membrane. This binding to the ER membrane initiates the translocation process.

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Golgi Apparatus

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o Correctly folded and assembled proteins in the ER are packaged into transport vesicles that pinch off from the ER membrane and move on microtubule tracks to the Golgi apparatus. The Golgi apparatus distributes the proteins that it receives from the ER. It processes the proteins, and the finished proteins are put in the trans Golgi network, which packages them in transport vesicles and dispatches them to their specific destinations in the cell.

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Mitochondria and Krebs Cycle

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o Occurs in the mitochondria. First, a glucose molecule goes through glycolysis, which produces 2 molecules of ATP and 2 molecules of pyruvate or pyruvic acid - each one of those either enters the Krebs cycle and the electron transport chain, (or if there is not enough oxygen it goes into lactic acid cycle - which does not produce much energy and produces lactic acid (runners get this and the lactic acid causes muscle soreness)). If there is enough oxygen, the pyruvate goes into the Krebs cycle. In this sequence, several things happen to the pyruvate to turn it into other compounds. This cycle produces some more ATP’s and other molecules called NADH and FADH2, after that it enters the stage that produces the most energy the electron transport chain - in this an electron is transported through proteins (called cytochromes) and, during this, protons (H+ ions) are produced, they create a pH gradient between the sides separated by the cristae (inner wall of the mitochondria

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Chloroplasts and Calvin Cycle

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o Occurs in the chloroplasts. First, light hits an electron in Photosystem II, that excites the electron and it goes through an electron transport chain to reach Photosystem I, during which it produces energy same way that the etc in respiration does, after that the electron gets hit by light again this time in Photosystem I, it gets excited again and goes through another ETC, producing some more ATP as well as NADPH. These molecules are then used in the Calvin cycle, in which carbon dioxide is absorbed by the plant from the air and used to form 3 carbon sugars which are then combined to form glucose, oxygen is released as a byproduct of that

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Compare Krebs and Calvin cycles

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