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Cells+Organelles 1

Why are cells small? Ensures adequate diffusion of waste products/nutrients.
Most eukaryote organelles belong to 3 main systems: Protein synthesis, secretion pathway and upgrade and degradation.
What does protein synthesis enable? Growth and differentiation.
Chromatin is packaged in two main ways: Euchromatin and Heterochromatin
What is euchromatin? A lightly packed form of chromatin (DNA, RNA and protein) that is enriched in genes
What is heterochromatin? A tightly packed form of DNA involved in the expression of genes
What is the function of the nucleolus? It assembles ribosomes at amplified ribosome genes.
What is one major pathway for secretion? RER----->Golgi----->Secretion/Plasma membrane
What are the functions of the rough endoplasmic reticulum? Site of membrane synthesis. Modifies proteins- adds sugars to them and trims them. Quality control- monitors correct folding Signals stress- e.g. when secretion is blocked
What is the structure of the Golgi? Complex stacks of flattened sacs close to the nucleus.
What is the function of the Golgi? Receives output of RER. Modifies lipids/proteins-grows sugar chains on proteins/adds Pi to some proteins. Sorts and packages cargo into distinct vesicles for export to other organelles.
Where do most microtubules emanate from? The centrosome
Where is the Golgi usually located? Close to the centrosome in the centre of the cell
What is the centrosome? A microtubule organising centre which contains two centrioles.
What is a lysosome? Low pH degradative bodies- contain hydrolytic enzymes
Describe the uptake mechanism in cells. Endocytosis (large particles by phagocytosis, molecules by pinocytosis). Membrane/cargo internalised delivered to endosomes and then passed to lysosomes for degradation. Some membrane is recycled back to the cell surface.
What is pinocytosis? The intake of small droplets of fluid by a cell by cytoplasmic engulfment. Occurs in many white blood cells and in certain kidney and liver cells.
What is autophagy? Portions of the cell itself can be walled off and digested in lysosomes.
What is an additional function of the RER? Membrane and functional components of lysosomes and endosomes are made here
Describe the process of protein degradation by proteasome. Junk protein is tagged (with ubiquitin). No membrane involved. Macromolecular complex. In cytoplasm not lysosomes.
What is a proteasome? A multi enzyme complex in cells that breaks down proteins into short peptides.
What is compartmentation? Internal membrane compartments with a range of specialised functions.
What is the advantage of compartmentation? Specialised reactions (some harmful) can be separated, concentrated and optimised.
Vesicle(s) transport... ...is a consequence of internal membranes. ...membranes and cargo between organelles.
What is invagination? The infolding of the wall of a solid structure to form a cavity. An example is when the ER coats the nucleoid to form the nuclear envelope.
What is the function of mitochondria? Produce most of the ATP supply. Enable cells to grow bigger. Present in all eukaryotic cells.
What is the structure of the mitochondria? Two membranes- inner membrane folded into interior. Contain their own DNA-divide by simple fission. All mitochondria come from the mother's egg.
Describe the structure of a microtubule. Thickness of a ribosome (25nm), dynamic proteins and made up of tubulin subunits.
What is the role of microtubules? Position/move organelles (vesicle tracks) and involved in cell division.
Describe the structure of microfilaments. Thinner than microtubules (7nm), a protein made up of actin subunits.
What is the role of microfilaments? Generates contractile forces enabling cells to move, parts of cell to move, cells to contract.
Describe the structure of intermediate filaments. Middle thickness (10nm), proteins made of keratins and lamins.
What is the role of intermediate filaments? Strength, support and some in the cytoplasm, some support the nuclear envelope.
Describe the role of the smooth endoplasmic reticulum. Connected domain of the RER membrane with no ribosomes and involved in lipid and steroid production and detoxification.
What is the role of peroxisomes? Break down some fatty acids, synthesise some specialised lipids (e.g. nervous system).
How do peroxisomes carry out their function? They do oxidative reactions using molecular oxygen. These generate hydrogen peroxide, and excess is broken down with catalase.
Describe the general structure of prokaryotes. Small, simple cells (about 1 micrometre). No internal membrane-enclosed organelles. No nucleus. Simple cell division.
Describe the general structure of eukaryotes. Larger cellular dimensions. Internal membranes with specialisation. Packaged DNA in nucleus. Contain endosymbiont organelles (mitochondria/chloroplasts).
What is the order of the stages of mitosis? Interphase, Prophase, Metaphase, Anaphase, Telophase and Cytokinesis.
What is apoptosis? Programmed cell death.
What defines the type of cell? Protein expression defines the speciality of the cell.
What are the four basic tissue types? Epithelia, Connective tissue, Muscle and Nervous tissue.
All cell types are derived from... ...A totipotent cell.
What are the four methods in which hormones can allow cells to communicate with each other? Endocrine, Paracrine, Neuronal and Contact Dependent.
Define paracrine. A hormone that is secreted by an endocrine gland that affects the function of nearby cells, rather than being transported distally by the blood or lymph.
What is an endocrine gland? A gland that manufactures one or more hormones and secretes them directly into the bloodstream.
What is a hormone? A substance that is produced in one part of the body by a gland and passes into the bloodstream and is carried to other organs, tissues where it acts to modify their structure or function.
What is a tight junction? Seals neighbouring cells together in an epithelial sheet to prevent leakage of molecules between them.
What is an adherens junction? Joins an actin bundle in one cell to a similar bundle in a neighbouring cell.
What is a desmosome? Joins the intermediate filaments in one cell to those in a neighbour.
What is a gap junction? Forms channels that allow small water-soluble molecules, including ions, to pass from cell to cell.
What is a hemidesmosome? Anchors intermediate filaments in a cell to the basal lamina.
What causes hypercholesterolemia? Defective uptake of lipoproteins.
What causes Cystic fibrosis? Misfolding of key protein
What causes hypertension? Defective cell-cell adhesion in the kidney.
What causes Congenital heart defects? Errors in cell migration during development.
What causes muscular dystrophy? Defective attachment of the plasma membrane to the cytoskeleton.
What causes Lysosomal storage disease? Defective intracellular transport of enzymes.
What causes cancer? Errors in cell division, migration, cell polarity, growth, etc...
Created by: robertspedding