1 - Cell Structure 🔬

• Features present in animal cells but not plant cells

  1) microvilli2) centrioles 3) cilia
• Ways water is used in a leaf cell [3]

  1) maintains turgidity2) reactant in photosynthesis3) hydrolysis reactions (or medium for chemical reactions to take place)
• Which range of sizes would include most eukaryotic cells?

  1 × 10^1 μm to 1 × 10^2 μm
• resolution of light microscope

  200 nm
• resolution of electron microscope

  0.5 nm
• advantages of using a light microscope over electron microscope

  1) portable2) easier to use; no technical training required3) able to see natural colours4) able to see living tissue5) particular tissues/organelles can be stained for better visibility6) no heavy metal staining
• explain and distinguish between resolution and magnification, with reference to light microscopy and electron microscopy

  - Magnification is the ability to make small objects seem larger, such as making a microscopic organism visible.- Resolution is the ability to distinguish between 2 separate points. As resolution increases, image clarity increases.
• outline the function and structure of a cell surface membrane

  1) 7 nm2) selectively permeable membrane that allows for the exchange of certain substances3) barrier between cytoplasm and external environment4) cell recognition (surface antigens)5) selecting substances that enter and leave the cell6) cell signalling7) cell-to-cell adhesion8) formation of hydrogen bonds with water for stability
• outline the function and structure of a nucleus

  1) 7 μm2) controls cell's activities3) surrounded by 2 membranes (nuclear envelope) which is continuous with the RER4) has nuclear pores
• outline the function and structure of a nucleolus

  1) 2.5 μm2) contains DNA3) synthesises ribosomes
• substances entering the nucleolus

  1) protein to make ribosomes2) ATP3) nucleotides
• substances leaving the nucleolus

  1) mRNA2) ribosomes for protein synthesis
• outline the function and structure of the rough endoplasmic reticulum

  1) series of flattened fluid-filled sacs2) have cisternae (flattened membrane disk)3) ribosomes are attached to it4) proteins made by ribosomes enter it 5) they're modified as they go through it5) small sacs (vesicles) break off of the RER and join together to form the golgi body
• outline the function and structure of the smooth endoplasmic reticulum

  synthesises lipids, steroids, cholestrol
• outline the function and structure of the golgi body

  1) stack of flattened sacs formed from the vesicles which had bud off from the RER2) have cisternae 3) packaging substances into vesicles for transport4) glycosylation5) phosphorylating proteins6) assembling polypeptides into proteins (quaternary structure)
• outline the function and structure of ribosomes

  1) 25 nm2) composed of 2 subunits3) carry out protein synthesis4) 80s - eukaryotes5) 70s - smaller, present in prokaryotes, mitochondria and chloroplasts
• outline the function and structure of lysosomes

  1) 0.5 μm2) single membrane3) contain digestive (hydrolytic) enzymes4) responsible for digestion of unwanted structures e.g. old organelles, toxic substances, metabolic waste5) also used to destroy viruses and bacteria
• outline the function and structure of mitochondria

  1) 0.5 to 1.0 μm2) carries out aerobic respiration3) ATP synthesis4) contain 70s ribosomes5) double-membrane; inner-membrane is folded inwards to form cristae6) outer-membrane is more permeable than inner due to presence of porins7) have small circular DNA
• outline the function and structure of microtubules

  1) ⍺ and β-tubulin form dimers, many dimers form 13 protofilaments, the protofilaments are in a ring and form a microtubule2) part of the cytoskeleton of the cell; gives shape to the cell

  
• outline the function and structure of centrioles (& centrosome)

  1) 9 triplets of microtubules form a centriole2) outside the nucleus of animal cells, 2 centrioles are present at right angles to each other in a region called centrosome (also referred to as an MTOC)3) assembles microtubules to produce the mitotic spindle

  
• outline the function and structure of chloroplasts

  1) 3 to 10 μm2) carries out photosynthesis3) contains starch grains, circular DNA and 70s ribosomes4) double-membrane5) ground substance is stroma which is the site of light-independent reactions6) light-dependent reactions take place in thylakoids (or grana)
• outline the function and structure of cell wall

  1) rigid as made of cellulose2) freely permeable3) prevents cell from bursting
• outline the function and structure of plasmodesmata

  1) allows transport of water, sucrose, amino acids, ions, etc between cells2) without crossing membranes3) this is movement through the symplast4) allows communication, signalling between cells

  
• outline the function and structure of vacuoles

  1) surrounded by partially permeable tonoplast2) helps regulate osmotic properties of cells3) has:PigmentsEnzymesSaltsOxygenMineral saltsOrganic moleculesCarbon dioxide
• prokaryotes


  1) unicellular

  2) don't contain nuclei

  3) 1-5 μm

  4) peptidoglycan cell walls

  5) contain 70s ribosomes

  6) naked circular DNA

  7) lack of membrane-bound organelles
• State the piece of equipment that can be used in the light microscope to work out the correct proportions of tissues

  eyepiece graticule