Cellular Processes (91156)

Cellular Processes (91156)

1. Cell Organelles

   • Plant Cells
     • Chloroplasts - oval shaped, found in leaf cells (particularly palisade cells), and are the site of photosynthesis
       • Chloroplast Structures
         • Double Membrane - Outer is simple and permeable allows for great rate of transport of materials needed for photosynthesis -Inner is semi-permeable, only allowing for the entry and exit of reactants/products of photosynthesis
         • Stroma - Clear fluid substance (so that sunlight can get through) - Where light independent reactions take place (CO2 and H2 join)
         • Lamellae - tubes connecting Grana to each other
         • Thylakoids + Grana - Thylakoids are individual flattened membranes arranged into disc shapes, light-dependent reactions occur here - Grana are stacks of thylakoids -Embedded in these membranes is chlorophyll, the light-absorbing pignment
       • Chloroplasts are more abundant in regions of the plant that are exposed to sunlight, such as those close to the top of the leaf (but beneath the epidermal layer)
     • Cell Wall - Made of cellulose bundled together, provide strength and structure for the cell
   • Animal Cells
     • Centrioles - involved in cell division,, composed of microtubules which extend to form spindles moving chromosomes apart
     • Cilia and Flagella - cellular projections, associated with movement in unicellular organisms and small animals
   • Both Cells
     • Mitochondria - oval shaped, found in most cells (particularly those with high-energy demands), and are the site of aerobic respiration
       • Mitochondria Structures
         • Matrix - the space between cristae which contains many enzymes
         • Cristae - inner membrane is folded into these to greatly increase the surface area for where Hydrogen Transfer chain reactions will occur
         • Double Membrane
       • Mitochondria are more abundant in animal cells, particularly those with high energy demands, eg. Muscle cells
     • Vacuoles - membrane-bound sacs filled with fluid
       • Lysosome - vacuole containing digestive enzymes, their job is to break down old organelles, digest bacteria engulfed by phagocytes/white-blood cells
     • Golgi Body - After proteins have been synthesized in the ER, they are sent here to be modified
     • Endoplasmic Reticulum (ER) - A network of membranes spanning across the cell that has multiple functions including being a transport system, carrying materials from one side of the cell to the other
       • Smooth - no ribosomes attached and is instead responsible for the production of lipids and steroids
       • Rough ER - ribosomes are attached, involved in protein production therefore, are common in cells that make/secrete proteins
     • Nucleus - contains DNA in the form of chromatin, which organises all cell processes
       • Nucleolus - inside the nucleus, produces the RNA components of ribosomes
     • Ribosomes - site of protein synthesis/ production
     • Plasma/Cell Membrane - A phospholipid layer with proteins embedded, and is semi-permeable (only allows some substances to enter/exit)

2. Cell Processes

   • Cell Division
     • DNA Replication
       • Happens before a cell divides
       • 1. DNA unwinds
       • 2. Nucleotides match up to exposed bases
       • 3. Enzymes check and correct errors
       • After replication 2 DNA molecules form a chromosomes, each identical half is called a chromatid, and are joined by a centromere
     • Mitosis - Cell division that produces two identical cells for growth, repair and maintenance.
       • 1. DNA replicates, nuclear membrane breaks down and spindles form
       • 2. Chromosomes line up at equator (cell centre)
       • .3 .Fibres contract, pulling chromatids to opposite ends of the cell
       • 4. Nuclear membranes form. Cell Divides
     • DNA Structure -
   • Respiration
     • Anaerobic Respiration
       • Occurs in the cell cytoplasm, not in Mitochondria
       • Oxygen is not involved in this reaction
       • Pyruvates formed in Glycolysis are broken down into lactic acid - this build up creates muscle fatigue
       • Only Glycolysis takes place
       • Substrates = Water + Glucose
       • Products = Lactic Acid + 2 ATP
     • Aerobic Respiration
       • Substrates = Oxygen + Water + Glucose
       • Products = Carbon Dioxide + Water + ATP + (heat energy)
       • Symbol Equation = C6H12O6 + 6O2 --> 6H20 + 6CO2 + 38ATP + (heat energy)
       • Three main chemical ENZYME-CONTROLLED pathways
         • 1. Glycolysis - Occurs in Cytoplasm of cell (not Mitochondria), Glucose broken down into 2 pyruvate molecules, 2 ATP molecules produced
         • 2. Krebs Cycle - occurs in matrix of Mitochondria, C02 (waste) and H atoms (used in next stage) are produced
         • 3. Electron Transfer Chain - occurs in Cristae of Mitochondria, H atoms from Krebs cycle are ionised and their electrons are 'bounced' through electron transfer chain, the energy released is used to form ATP from ADP, electrons are then returned to H atoms to combine with O2 and form H20 (product)
           • To become ATP (Adenosine Triphosphate), ADP (Adenosine Diphosphate) gains a phosphate
     • How organisms get energy to fuel life processes
   • Photosynthesis
     • Occurs only in Plants
     • Products = Glucose + Water + Oxygen
     • Substrates = Carbon Dioxide + Water
     • Symbol Equation: 12H2O + 6CO2 -- (Sunlight +Chlorophyll) --> 6H2O + C6H12O6 + 6O2 OR 6H2O + 6CO2 -- (Sunlight +Chlorophyll) --> C6H12O6 + 6O2
     • Two main chemical ENZYME-CONTROLLED pathways
       • 1. Light-Dependent Reacton - takes places in grana of chloroplasts, sunlight is absorbed in thylakoid membrane, water is splt into Hydrogen H (used in next stage) and Oxygen 02 (Waste)
       • 2. Light-Independent (Calvin Cycle) - Occur in stroma of chloroplast, CO2 and H enter the cycle and after extensive arrangement, Glucose (C6H12O6) is formed as the final product
     • Rate of Photosynthesis Influences
       • Temperature
       • Light Intensity + Wavelength
       • Substrate Concentration (CO2)

3. Enzyme Activity

   • Factors that infleunce Enzyme Activity
     • Temperature
     • pH
     • Substrate Concentration

4. Transport of Materials

   • Active Transport
     • Cytosis
       • Endocytosis
         • Pinocytosis
         • Phagocytosis
       • Exocytosis
   • Passive Transport
     • Diffusion
       • Facillitated Diffusion
       • Osmosis