Cells: Structure and Function Notes PDF

 Cells Cells: the basic structural and functional units of every organism ○ All cells: 1. Are bound by a plasma membrane 2. Contain cytosol 3. Contain chromosomes 4. Contain ribosomes  Cells There are two types of cells: prokaryotes...

 Cells Cells: the basic structural and functional units of every organism ○ All cells: 1. Are bound by a plasma membrane 2. Contain cytosol 3. Contain chromosomes 4. Contain ribosomes  Cells There are two types of cells: prokaryotes and eukaryotes Prokaryotes Eukaryotes Domains Bacteria and Protists, fungi, Archaea animals, and plants DNA is in the nucleoid DNA is in the nucleus region Contain membrane Generally smaller in bound organelles size than eukaryotes Organelles  Organelles Organelles: membrane bound structures in eukaryotes Two classifications: Endomembrane organelles 1. Nuclear envelope 2. Endoplasmic reticulum 3. Golgi complex 4. Lysosomes 5. Vesicles/Vacuoles 6. Plasma membrane Energy organelles 1. Mitochondria 2. Chloroplasts  Compartmentalization Compartmentalization in organelles allows for different metabolic reactions to occur in different locations ○ Increases surface area for reactions to occur ○ Prevents interfering reactions from occuring in the same location Topic 2.10  Unique Cell Components Plants Animals Chloroplasts Lysosomes Central vacuole Centrosomes Cell wall Flagella Plasmodesmata Endomembrane Organelles  Nucleus Contains chromosomes (genetic information) ○ Enclosed by the nuclear envelope Double membrane ○ Has pores Pores regulate entry and exit of materials from the cell  Nucleus Contains a nucleolus Dense region of the nucleus where ribosomal RNA (rRNA) is synthesized ○ rRNA is combined with proteins to form large and small subunits of ribosomes ○ Subunits exit via nuclear pores Assemble into ribosomes Ribosomes translate messages found on mRNA into the primary structure of polypeptides  Review In order for DNA to leave the nucleus, it must first be transcribed by RNA polymerase into messenger RNA (mRNA). The mRNA transcript must then be modified before leaving the nucleus to the cytoplasm. In the cytoplasm, the ribosomes decode the information in mRNA and form continuous chains of amino acids, thus forming a protein. This process of DNA → RNA → protein is known as transcription and translation and will be the main concepts covered in Unit 6. Answer questions 1-3.  Ribosomes Comprised of ribosomal RNA and protein ○ Function: synthesize proteins Note: some texts do not classify ribosomes as organelles because they are not bound by a membrane  Ribosomes Can be found in two locations: 1. Cytosol ○ Proteins produced here generally function only within the cytosol (i.e. enzymes) ○ Known as “free ribosomes” 2. Bound to the endoplasmic reticulum or nuclear envelope ○ Proteins produced here can be secreted from the cell Leave via transport vesicles  Endoplasmic Reticulum A network of membranous sacs and tubes ○ Functions: Synthesizes membranes Compartmentalize the cell to keep proteins formed in the rough ER separate from those of free ribosomes  Endoplasmic Reticulum Two types: rough and smooth  Endoplasmic Reticulum 1. Rough ER ○ Contains ribosomes bound to the ER membrane 2. Smooth ER Contains no ribosomes Synthesizes lipids, metabolizes carbohydrates, and detoxifies the cell  Golgi Complex Contains flattened membranous sacs called cisternae Separate the sacs from the cytosol Each cisternae is not connected Has directionality ○ Cis face: Receives vesicles from the ER ○ Trans face: Sends vesicles back out into cytosol to other locations or to the plasma membrane for secretion  Golgi Complex Functions: Receives transport vesicles with materials from the ER Modifies the materials Ensures newly formed proteins are Sorts the materials folded correctly or Adds molecular tags modified correctly Packages materials into new transport vesicles that exit the membrane via exocytosis  Lysosomes Membranous sac with hydrolytic enzymes Function: ○ Hydrolyzes macromolecules in animal cells ○ Autophagy: lysosomes can recycle their own cell’s organic materials Allows the cell to renew itself Peroxisomes Similar to lysosomes Membrane bound metabolic compartment ○ Catalyze reactions that produce H2O2 Enzymes in peroxisomes then break down H2O2 to water  Vacuoles Large vesicles that stem from the ER and Golgi Selective in transport Types: Food vacuole Form via phagocytosis (cell eating) and then are digested by lysosomes Contractile vacuole Maintain water levels in cells Central vacuole Found in plants ○ Contains inorganic ions and water ○ Important for turgor pressure  Practice FRQ 1. Hepatitis C is a virus that attacks the liver and can cause liver disease. Liver disease has been linked to a reduction in albumin levels in patients analyzed. Albumin is an important protein in humans. It functions primarily to regulate oncotic pressure of blood, which is important for the regulation of fluids in vessels of the body and tissue repair. On average, patients with liver disease show a 10-30% decrease in blood-albumin levels. (a) Identify the organelle in liver cells that is most likely being affected by hepatitis C and (b) justify your reasoning.  Practice FRQ 2. In humans, pancreatic cells synthesize the protein insulin in the endoplasmic reticulum (ER). Patients diagnosed with type 1 diabetes have immune systems that mistakenly attack their pancreatic cells. Therefore, these patients cannot produce the hormone insulin and have to take medications to introduce insulin into their bodies. (a) Describe how insulin would be produced in a normal functioning (non-type 1 diabetes) pancreatic cell. Energy Organelles  Endosymbiont Theory Endosymbiont Theory: the theory that explains the similarities mitochondria and chloroplasts have to a prokaryote ○ Theory states that an early eukaryotic cell engulfed a prokaryotic cell Prokaryotic cell became an endosymbiont (cell that lives in another cell) Became one functional organism Topic 2.11  Endosymbiont Theory Evidence: Double membrane Ribosomes Circular DNA Capable of functioning on their own Topic 2.11  Mitochondria Site of cellular respiration Structure of the double membrane: ○ Outer membrane is smooth ○ Inner membrane has folds called cristae Divides the mitochondria into two internal compartments and increases the surface area  Mitochondria 1. Intermembrane: space between inner and outer membrane 2. Mitochondrial matrix: enclosed by inner membrane Location for the Krebs cycle Contains: ○ Enzymes that catalyze cellular respiration and produce ATP ○ Mitochondrial DNA ○ Ribosomes  Mitochondria The number of mitochondria in a cell correlates with metabolic activity Cells with high metabolic activity have more mitochondria ○ Example: cells that move/contract  Chloroplast Specialized organelles in photosynthetic organisms ○ Site of photosynthesis ○ Contains the green pigment chlorophyll Inside of its double membrane: ○ Thylakoids Membranous sacs that can organize into stacks called grana Light dependent reactions occur in grana  Chloroplast Stroma: fluid around thylakoids ○ Location for the Calvin cycle ○ Contains Chloroplast DNA Ribosomes Enzymes The Cytoskeleton  Cytoskeleton A network of fibers throughout the cytoplasm ○ Give structural support (especially for animal cells) and mechanical support: Anchor organelles Allow for movement of vesicles and organelles and/or the whole cell Movement occurs when the cytoskeleton interacts with motor proteins  Cytoskeleton There are 3 types of fibers in the cytoskeleton: 1. Microtubules 2. Microfilaments 3. Intermediate filaments  Microtubules Hollow rod-like structures made of the protein tubulin Grow from the centrosome ○ Assist in microtubule assembly  Microtubules Functions: Serve as structural support (think: tracks) for the movement of organelles that are interacting with motor proteins Assist in the separation of chromosomes during cell division Cell motility (i.e. cilia and flagella)  Microfilaments Thin solid rods made of the protein actin Functions: Maintain cell shape ○ Bear tension Assist in muscle contraction and cell motility ○ Actin works with another protein called myosin to cause a contraction Division of animal cells ○ Contractile ring of the cleavage furrow  Intermediate Filaments Fibrous proteins made up of varying subunits Permanent structural elements of cells Functions: Maintain cell shape Anchor nucleus and organelles Form the nuclear lamina ○ Lines the nuclear envelope  Practice FRQ 1. You are working in a research lab and your goal is to determine the effect that alcohol has on the liver. You design an experiment where you expose samples of liver tissues to varying concentrations of alcohol as follows: Sample Concentration of alcohol Duration of exposure Sample 1 0.25 mg/mL 20 minutes Sample 2 0.35 mg/mL 20 minutes Sample 3 0.45 mg/mL 20 minutes After exposure to the alcohol, you analyze the liver samples. In all samples you find that the alcohol has been broken down (detoxified). However, in sample 3 you find damage to organelles has occured due to the high concentration of alcohol. (a) Identify one organelle in the liver that could be responsible for the detoxification of the alcohol in all three samples. (b) In sample 3 identify the organelle that would most likely be responsible for removing the damaged parts of organelles and (c) describe the steps it would take to do so.