Complete W3 - Cell organelles BMD116 CELLS QMUL PDF

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Complete W3 - Cell organelles BMD116 CELLS QMUL...

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Cell organelles and variations on a theme LO 1: Describe the role for named sub-cellular organelles

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1. What is the definition of a cell? Small units bound by a plasma membrane (possibly a cell wall) 2. What do cells contain? Aqueous cytoplasm Structural support - cytoskeleton Membrane bound organelles

3. Briefly describe the features of the cell surface. All cells are surrounded by a plasma membrane Single membrane just 2 molecules thick Membrane is selectively permeable – defines what is in and out of the cell  Allows the cell to maintain order (environment of low entropy) in a high entropy disordered universe outside the cell 4. Why is the plasma membrane selectively permeable?

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Because lipids are amphipathic – they have hydrophobic and hydrophilic parts – this determines how the membrane is structured.

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Fluid mosaic model – integral and peripheral membrane proteins transport hydrophilic solutes 5. What is the role of the cell wall in plants and bacteria?

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Rigid structural support Limits passage (in addition to the plasma membrane) of molecules in to/out of the cell 6. Describe the features of the cell wall in bacteria.

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Composed of peptidoglycans Can be surrounded by a gelatinous polysaccharide layer – Glycocalyx (can be referred to capsule or slime layer) 7. We can stain bacteria with Gram’s stain. Describe how we can then classify the bacteria.

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Gram +ve = thick peptidoglycan layer to cell wall prevents stain being washed out – purple Gram -ve = thin peptidoglycan layer (+lipopolysaccharide layer) allows stain to be washed out - pink

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Tiny cellular structure that performs specific functions within a cell. Embedded within the cytoplasm of eukaryotic and prokaryotic cells In more complex eukaryotic cells, organelles are often enclosed by their own membrane.

9. What is the function of the nucleolus?  

Site of ribosomes Contains ribosome genes (rRNA) and proteins for ribosome formation 10.

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Nucleus and nucleolus separated from cell cytoplasm Double membrane (nuclear envelope) around nucleaus with pores Pores allow controlled movement into and out of the nucleus. No membrane around nucleolus

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Describe the features of the nuclear membrane.

Describe the location, role and structure of centrioles.

Only in animal cells Adjacent to nucleus Perpendicular pair of specialist microtubules Organise mitotic (or meiotic) spindle

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What are the features of the mitochondria?

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Double mitochondrial membrane Inner membrane highly folded into cristae – increase surface area to increase enzymes for respiration Mitochondria have their own mitochondria DNA – Maternally inherited 13. What is the main function of mitochondria? Mitochondria contains series of oxidative enzymes Aerobic catabolism of fuels (carbohydrates, fatty acids, amino acids, proteins) Harness energy from oxidative phosphorylation (ETC) to generate ATP

14. What are the other functions of mitochondria? 

Generate and metabolise reactive

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oxygen species (ROS) and free radicals  Can be good or bad – good for cell signalling but don’t want it around too often Mediate programmed cell death – apoptosis Calcium store

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15. What are the synthetic organelles? Chloroplasts – photosynthesis Ribosomes – translation of proteins Endoplasmic reticulum – protein and lipid synthesis Golgi apparatus – protein processing, sorting and secretion Secretory vesicles – secretion 16.

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What is the role of the rough endoplasmic reticulum?

Protein synthesis, protein transport and sorting Proteins made by the bound ribosomes cross the rough ER membrane  golgi body

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Proteins fold and modified in ER Have sugars added by glycosylation to protect proteins Misfolded proteins sent for destruction 17.

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Lipid synthesis Detoxification (lots are found in liver) Major site for calcium storage 18.

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Describe the pathway of proteins/lipids from the RER.

Molecules enter cis face from ER Exit from transface of the golgi Move via vesicular trafficking

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What is the main role of the golgi body?

Where proteins and lipids are processed and sorted prior to:  Insertion into plasma membrane  Incorporation into organelles  Secretion 19.

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Describe the role of smooth endoplasmic reticulum?

What is vesicular trafficking?

Vesicle buds off from one membrane Vesicle passes through the cytoplasm and fuses with another membrane Traffics both luminal and membrane content of vesicle 21.

What are the two secretory pathways?

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Exocytosis – constitutive (not regulated by signalling) – eg. Extracellular matrix proteins by fibroblasts Secretory vesicles – regulated by signals (eg hormones or growth factors) 22.

What are the digestive organelles?

 Endosomes  Lysosomes  Peroxisomes LO 2: Understand that differences occur between cell types related to function

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1. How do cells differ? Size Shape/structure Function 2. Name examples of how the size and shape correlates with functions. Erythrocyte (red blood cells) – small and flattened to enter smallest capillaries Fibroblast – spindle shaped to form connective tissue, extracellular matrix acting as a buffer to tissues Keratinocyte – cuboid to form skin barrier Spermatozoa – flagella so it can move Melanocyte – dendritic cell (finger like projections) for cell communication Neuronal cells – dendritic

3. Not all eukaryotic cells have a nuclei. Describe examples of these cases and its function? All mammals lack nucleus in erythrocytes – red blood cells need to be small in size and increase surface area and volume ratio to collect oxygen Most non-mammalian vertebrates have nucleated red blood cells. Lens fibre cells in the eye have no nuclei – nucleus may get in the way of light transmission 4. Not all cells have the same number of mitochondria. Give examples to back this statement. Hepatocytes (liver cells) have around 2000 mitochondria per cell – accounting for 20% of cell volume

 Unicellular organisms usually have a single mitochondrion  Erythrocytes and some unicellular eukaryotes have no mitochondria. (Have to rely on glycolysis for their metabolism – can be aerobic and anaerobic)

LO 3: Explain the differences between prokaryotes and eukaryotes

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1. Classification of eukaryotes and prokaryotes refers to organisms not cells. 2. What is the main difference between a prokaryotic and eukaryotic organism? Prokaryotes – do not have a nucleus Eukaryotes – have a nucleus (nucleus is surrounded by a double membrane envelope) 3. What are the phyla classifications of multicellular and unicellular eukaryota? Multicellular  Animals  Plants  Fungi Unicellular  Yeast  Amoeba

4. There are more phyla in the prokaryotes than eukaryotes. Note: eukaryotes have 5, prokaryotes: more than 12 5. What are the structures that prokaryotes do not have but eukaryotes do? Prokaryotes do not have ANY MEMBRANE BOUND ORGANELLES. NO:  Nucleus  Mitochondria  Endoplasmic reticulum  Golgi apparatus 6. What is the only common organelle between a prokaryotic organism and eukaryotic organism? Ribosome 7. What is the nucleoid? Bacterial chromosome; single circular molecule of ‘naked’ DNA (no histones) 8. Describe the differences in metabolism (breakdown of glucose to produce energy) in eukaryotic and prokaryotic organisms.

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In prokaryotes, glycolysis and TCA cycle occurs in cytosol. The proton gradient for ATP production being across the cell’s surface (plasma membrane) rather than the inner membrane of the mitochondrion.

9. Eukaryotes include both unicellular (amoeba) and multicellular organisms. However, prokaryotes are usually unicellular. Multicullar prokaryotes exist but are rare. Name an example of a multiceullular prokaryotic organism. Cyanobacteria  Some bacteria have multicellular stages (eg. myxobacteria) 10. Which cells undergo meiosis? Germ cells 11. Which component of the ribosome is enzymatic? RNA is where the catalytic activity lies. 12. How does a vesicle differ from a lipid micelle? Vesicle is composed of a lipid bilayer whereas a lipid micelle is not.

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13. Why do mitochondria have their own DNA? Mitochondrial DNA originates from a symbiotic relationship with a prokaryotic organism.

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14. Why is the mitochondria DNA maternally inherited? Male mitochondria in sperm do not enter the oocyte. Only the DNA in the acrosomal head of the sperm enters the oocyte. Paternal mitochondria power the sperm but does not contribute to the zygotic mitochondria....