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Cells+Organelles
Cells+Organelles 1
| Question | Answer |
|---|---|
| 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
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