Cells

• there are 2 types of cells. prokaryotic and eukaryotic
• prokaryotic = bacteria
• Eukaryotic = fungi, animals, plants
• all cells are bounded by a selective barrier called a plasma membrane
• inside all cells there is a semifluid jellylike substance called cytosol
• all cells contain chromosomes which carry genes in the form of DNA
• all cells have ribosomes which are tiny complexes that make proteins according to the instructions from genes
• eukaryotic have membrane bound organells
• prokaryotic cells do not have membrane bound organelles
• the fine detail of cells is called its ultra structure
• a eukaryotic cell has an extensive and elaborately arranged internal membranes that divide the cell into compartments
• the cells organelles provide different local environments that facilitate specific metabolic functions
• mitochondria occur in very large numbers that are metabolically active
• size of a mitochondria is approx 1um wide and up to 10um long
• each mitochondria is bounded by a double membrane
• in mitochondria the outer membrane is a smooth continuous boundary
• in mitochondria the inner membrane is extensively folded to form partitions called cristae. providing greater surface area for ATP synthesis
• the mitochondria are the sites of ATP synthesis by aerobic respiration
• chloroplasts are bigger than mitochondria and are the organelle of photosynthesis
• chloroplasts belong to a group of organelles called plasmids. that contain pigment called chlorophylls and carotenoids
• chloroplasts are enclosed by a double membrane
• in chloroplasts the outer membrane is a smooth continuous boundary
• in chloroplasts the inner membrane gives rise to strands of an internal system of branching membranes called lamellae
• in chloroplasts, flat circular stacks called thylakoids are stacked into grana and are filled with chlorophyll. chlorophyll absorbs light energy for photosynthesis
• the double membrane of a chloroplast surrounds a matrix called the stroma
• endoplasmic reticulum is a network of folded membranes forming flattened sacs in the cytoplasm
• E Reticulum originates from outer membrane on nucleus
• Rough ER has ribosomes attached and is the site of protein synthesis
• vesicles containing protein are pinched off the RER and the synthesised protein us transported to the golgi apparatus
• Smooth ER has no ribosomes and is involved in lipid metabolism
• ribosomes are composed of protein and rRNA and are free in the cytoplasm or attached to RER
• ribosomes are the site of protein synthesis
• golgi apparatus consists of flattened membrane sacs called cristernae
• golgi apparatus collects proteins or lipids made by RER and SER
• vesicles are pinched off the golgi RER and move to the golgi apparatus to fuse together and form cisternae on the forming face
• inside the cisternae the primary protein is modified

  • carbohydrates added to form glycoproteins/lipoproteins. stabilising structure

  • final stages of enzyme formation occur

  • polypeptides dorm quaternary proteins

  • prosthetic groups may be added
• vesicles containing glycoprotein are pinched off the mature face of golgi apparatus and move towards the plasma membrane fusing here and releasing its contents out of the cell. process is called exocytosis
• lysosomes are small vesicles produced by Golgi apparatus
• lysosomes are bounded by a single membrane and contain a mixture of hydrolytic digestive enzymes
• lysosomes remain in the cell and are involved in intracellular digestion