4 Organelles & Cell Structure (DIY)

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Created by
nanihamster

Cards (36)

  • (E) NON-MEMBRANOUS ORGANELLE: Ribosomes
    • 80S, consisting of a 40S small subunit, and a 60S large subunit
    • Free ribosomes → found freely floating in the cytosol
    • Function within the cytosol as soluble proteins or enzymes
    • Bound ribosomes → attached to the outside of the rough endoplasmic reticulum (RER)
    • Insertion into membranes (embedded proteins) + packaging within certain organelles 
    • Export from the cell
    • Site of protein synthesis (amino acids are joined together → polypeptide chain via peptide bonds)
  • (E) NON-MEMBRANOUS ORGANELLES: Centrioles (1)
    • Found within the centrosome region, located close to the nucleus, existing as a pair of cylindrical, rod-like structures positioned at right angles
    • Consists of 9 triplets of microtubules arranged in a ring
    • Microtubules maintain the shape of a cell
    • Involved in intracellular transport
    • Forms the structural component of centrioles, cilia and flagellum
    • chromosome movement in cell division
  • (E) NON-MEMBRANOUS ORGANELLES: Centrioles (2)
    • Plays a role in nuclear division in animal cells, functioning as a microtubule organising centre (MTOC) → separation of homologous chromosomes and sister chromatids towards opposite poles of the cell during nuclear division
    • Plants lack centrioles, but still have well-organised microtubules
  • (E) NON-MEMBRANOUS ORGANELLES: Endoplasmic Reticulum
    • Extensive interconnected network of membranous tubules and sacs called cisternae
    • Single membrane separates ER’s internal compartment from the cytosol (continuous with the nuclear membrane)
    • Consists of: Rough Endoplasmic Reticulum, Smooth Endoplasmic Reticulum, Sarcoplasmic Reticulum
  • (E) SINGLE-MEMBRANE ORGANELLES: Rough Endoplasmic Reticulum (RER)
    • Extensive network of flattened membranous sacs with ribosomes attached to its cytoplasmic surface
    • Transports proteins which are synthesised by its bound ribosomes for secretion out of the cell/ targeted for insertion into the plasma membrane
    • Modification of proteins (Formation of glycolipids and glycoproteins)
  • (E) SINGLE-MEMBRANE ORGANELLES: Smooth Endoplasmic Reticulum (SER)
    • Lacking ribosomes on its membrane surface, but its cisternae is much more tubular than that of the RER
    • Contains many embedded enzymes that catalyse the metabolism of carbohydrates and synthesis of lipids
    • Detoxify products of natural metabolism, drugs and overloads of ethanol in liver cells
  • (E) SINGLE-MEMBRANE ORGRANELLES: Sarcoplasmic Reticulum
    • Only exists in muscle cells
    • Stores Calcium ions and orderly releases Ca2+ ions to allow for the controlled contraction of muscle cells
  • (E) SINGLE-MEMBRANE ORGANELLES: Golgi Apparatus (1)
    • A stack of flattened, membrane-bound sacs called cisternae and associated vesicles → golgi vesicles which are enclosed by a single membrane
    • Consisting of a cis (forming) face and a trans (maturing) face
    • Modifying, sorting and packaging molecules before transporting them to different parts of the cells for use and for secretion out of the cell
    • Enzymes in the GA are responsible for further modifying the existing glycolipids and glycoproteins from the RER (modifies the carbohydrate component)
  • (E) SINGLE-MEMBRANE ORGANELLES: Golgi Apparatus (2)
    • Formation of new cell wall of plant cells --> polysaccharides are secreted from the trans face of the GA and transported by membrane-bound transport vesicles that eventually fuse with the cell surface membrane --> formation of cell plate
    • Formation of Lysosomes
  • (E) SINGLE-MEMBRANE ORGANELLES: Lysosomes (1)
    • Small spherical membrane-bound vesicle containing hydrolytic enzymes that originated from the GA
    • Digestion of material taken in by endocytosis → lysosomes fuse with vesicles formed by endocytosis to digest the contents within the endocytic vesicles
    • Useful products: absorbed and assimilated into the cytoplasm
    • Harmful products: released into the external medium by exocytosis
  • (E) SINGLE-MEMBRANE ORGANELLES: Lysosomes (2)
    • Autophagy → breakdown of unwanted structures within the cell
    • Organic products are returned to the cytoplasm for reuse
    • Release of enzymes outside of the cell by exocytosis → breakdown of extracellular content
    • Autolysis → contents of lysosomes are released within the cell due to injury → self-digestion of the cell
  • (E) DOUBLE-MEMBRANE ORGANELLES: Nucleus
    • Chromatin
    • Nucleolus
    • Nuclear Envelope
  • (E) DOUBLE-MEMBRANE ORGANELLES: Nucleus - Chromatin
    • Heriditary genetic material of the cell
    • Exists as thin thread-like structure of chromatin when the cell is not dividing
    • Loosely coiled: euchromatin (active in RNA synthesis)
    • Tightly coiled: heterochromatin (stained more intensely)
  • (E) DOUBLE-MEMBRANE ORGANELLES: Nucleus - Nucleolus
    • most visible structures in a non-dividing nucleus as it is much denser than surrounding chromatin
    • Not membrane bound, and multiple can be found within a eukaryotic cell
    • Site of synthesis of rRNA
    • Site of assembly of ribosomal proteins with rRNA to form small and large subunit of ribosomes
  • (E) DOUBLE-MEMBRANE ORGANELLES: Nucleus - Nuclear Envelope
    • Contains nuclear pores which act as channels for the movement of molecules between the nucleus and cytoplasm
    • Outer membrane is continuous with the membrane of the ER
    • Stores the hereditary material (DNA) of an organism
    • Controls the cellular activities of the cell by regulating protein synthesis
    • through the use of genes as templates for the synthesis of mRNA (transcription)
    • used as templates for protein synthesis (translation)
  • (E) DOUBLE-MEMBRANE ORGANELLES: Mitochondrion
    • Spherical/ rod-shaped, with the semi-fluid matrix being enclosed by a double membrane
    • Outer membrane is smooth, Inner membrane is highly infolded to form numerous cristae (provide a larger surface area for attatchment of enzymes and other electron carriers involved in cellular respiration)
    • Space between membranes: intermembrane space
    •  Fluid matrix contains 70S ribosomes, circular DNA and various enzymes
    • The site of cellular respiration where nutrients are oxidised to synthesise ATP (Aerobic respiration)
  • (E) DOUBLE-MEMBRANE ORGANELLES: Chloroplast
    • Lens-shaped organelle, where its fluid-filled stroma is enclosed by a double membrane, each made of a phospholipid bilayer
    • Stroma contains 70S ribosomes, circular DNA and various enzymes involved in photosynthesis and starch grains
    • STRUCTURE: thylakoid (series of interconnected sacs) → Grana (stacked thylakoids) → Stacks of grana (joined by intergranal lamallae)
    • Photosynthetic pigments and enzymes involved in photosynthesis are located in the thylakoid membrane
    • Site of photosynthesis
  • Prokaryotes - Bacterial Cell
    • Small and unicellular
    • Lacks membrane-bound organelles
  • (P) Peptidoglycan Cell Wall
    • Consists of a polymer called peptidoglycan - long polysaccharide chains cross-linked by short chains of amino acids
    • Protects the bacterial cell from osmotic lysis
  • (P) Glycocalyx
    • A layer of polysaccharides  surrounding the peptidoglycan cell wall
    • Slime layer/ capsule
    • Protects the bacteria from being engulfed via phagocytosis by white blood cells → decreases their recognition by them
    • Enables bacteria to adhere to particular surfaces
  • (P) Cell Surface Membrane
    • Made up of a phospholipid bilayer
    • Compartmentalisation
    • Where proteins and enzymes used during photosynthesis/ respiration of eukaryotic cells are found
    • Folds inwards to form mesosome → site of respiration with functions like the mitochondria
  • (P) Appendages
    1. Fimbriae: short, bristle-like fibres extending from the cell surface
    • Involved in the attachment to surfaces/ other bacteria/ organisms
    1. 2) Pili: longer than fimbriae but fewer in numbers
    • Involved in making contact with a surface and retracting to pull the bacteria forward towards the contacted surface
    1. 3) Flagellum: long appendages for mobility
    • For movement
  • (P) Genetic Material
    1. Bacterial chromosome: single circular DNA, double-stranded and associated with histone-like proteins
    2. 2) Plasmids: much smaller, double-stranded, circular, extra-chromosomal DNA
    • Autonomously replicating DNA
  • (P) Ribosomes
    • 70S, consisting of a small 30S subunit, and a large 50S subunit
    • Protein synthesis
  • (P) Storage Granules
    • Storage organelles
    • Store nutrients and chemical reserves
  • Describe the processes that occur in the Golgi body
    1. Glycosylation occurs whereby oligosaccharides / short sugar chains / carbohydrates are added to proteins and lipids to form glycoproteins and glycolipids respectively
    2. Sorting and packaging of proteins into secretory vesicles for secretion out of the cell via exocytosis;
    3. Sorting and packaging of hydrolytic enzymes into vesicles that can form lysosomes;
    4. In plant cells, Golgi body is the site for synthesis of polysaccharides such as pectin (a component in plant cell wall) and then transported in vesicles to the cell surface membrane.
  • Describe the role of the vesicles that fuse with the forming face of the Golgi body
    1. The vesicles transport proteins and lipids from the rough and smooth endoplasmic reticulum to the Golgi body;
    2. When transport vesicles fuse with forming face of the Golgi body, contents of vesicles (e.g. proteins, lipids, glycoproteins, glycolipids) enter lumen of Golgi apparatus for further chemical modification.
    3. Fusion of transport vesicles with Golgi body also replenishes membrane of Golgi body
  • Outline 2 roles for the vesicles that are formed at the maturing face of the golgi body (1)
    1. These vesicles may be used to form lysosomes which contain hydrolytic enzymes
    2. Lysosomes fuse with phagocytic vesicles to digest the contents (e.g. foreign particles & food) within the vesicles.
  • Outline 2 roles for the vesicles that are formed at the maturing face of the golgi body (2)
    1. Secretory vesicles;
    2. fuse with cell surface membrane to release contents to the external environment via exocytosis
  • Outline 2 roles for the vesicles that are formed at the maturing face of the golgi body (3)
    1. Vesicles containing cell wall materials (e.g. pectins and certain non-cellulose polysaccharides)
    2. fuse to form the new cell plate during the synthesis of new plant cell walls;
  • Outline 2 roles for the vesicles that are formed at the maturing face of the golgi body (4)
    1. Vesicles with proteins embedded on the vesicle membrane
    2. fuse with the cell surface membrane, resulting in these proteins embedded on the cell surface membrane (e.g. receptors, glucose transport proteins etc.)
  • Lysosome formation
    1. Nucleus contains genes coding for hydrolytic enzymes
    2. Ribosomes at the RER translate mRNA
    3. Hydrolytic enzymes are chemically modified in the RER lumen
    4. Transport vesicles bud off from the RER
    5. Hydrolytic enzymes undergo modification, sorting, and packaging in the Golgi apparatus
  • Describe how lysosomes are formed in the cell. In your answer, include the identities and roles played by three other organelles (1-3)
    **Need pts. 1, 2, 5
    1. Nucleus contain genes that code for the hydrolytic enzymes (found in lysosomes), which are transcribed within nucleus to form mRNA.
    2. Ribosomes at the rough endoplasmic reticulum (RER) translate the mRNA to synthesize hydrolytic enzymes.
    3. The hydrolytic enzymes are chemically modified within the lumen of the RER;
  • Describe how lysosomes are formed in the cell. In your answer, include the identities and roles played by three other organelles. (4-5)
    1. Transport vesicles containing the hydrolytic enzymes bud off from the RER and transport the hydrolytic enzymes to the Golgi apparatus
    2. At the Golgi apparatus, the hydrolytic enzymes undergo further chemical modification, sorting and packaging into vesicles that can form lysosomes.
  • What is the role of a lysosome (1-3)
    1. Lysosomes fuse with endocytic vesicles containing food, releasing the hydrolytic enzymes to hydrolyse the contents of the endocytic vesicle;
    2. Lysosomes fuse with phagocytic vesicles containing bacteria, releasing hydrolytic enzymes to destroy bacteria;
    3. Lysosomes can also fuse with autophagic vesicles which contain worn-out organelles to break down the organelles during autophagy;
  • What is the role of a lysosome (4-5)
    1. Hydrolytic enzymes can be released within the cell during autolysis to result in cell death, e.g. breakdown of obsolete cells during metamorphosis in tadpoles;
    2. Hydrolytic enzymes of lysosomes can be released out of the cell via exocytosis for breakdown of extracellular structures.