Cell structure and organisation

• Define eukaryotic cell


  A type of cell that contains a true nucleus along with membrane-bound organelles
• Describe the structure of the nucleus.


  Surrounded by nuclear envelope, a semi-permeable double membrane

  Nuclear pores allow substances to enter/exit

  Dense nucleolus made of RNA and proteins assembles ribosome
• Describe the function of the nucleus


  Contains DNA coiled around chromatin into chromosomes

  Controls cellular processes
• What is chromatin?


  A DNA protein complex found in eukaryotic cells
• Describe the structure of mitochondria


  Surrounded by double membrane, mitochondrial envelope

  Folded inner membrane forms cristae (large surface area)

  Fluid matrix contains mitochondrial DNA, respiratory enzymes, lipids and proteins
• Describe the function of mitochondria


  Site of aerobic respiration to produce ATP
• Describe the structure of the endoplasmic reticulum (ER)


  Series of flattened membrane-bound sacs (cisternae) within the cytoplasm, continuous with the nuclear envelope
• Describe the function of the smooth endoplasmic reticulum (SER)


  Lipid synthesis
• Describe the function of the rough endoplasmic reticulum (RER)


  Many ribosomes attached for protein synthesis and transport
• Describe the structure of ribosomes


  Made from rRNA and proteins

  Found free in the cytoplasm or associated with the RER
• Describe the function of ribosomes


  Site of protein synthesis (translation)

  Large subunit joins amino acids

  Small subunit reads RNA
• Describe the structure of the Golgi body


  Planar stack of membrane-bound, flattened sacs

  Molecules are processed in cisternae.

  Vesicles bud off trans face via exocytosis
• Describe the function of the Golgi apparatus


  Modifies and packages newly made proteins for export

  Synthesises glycoproteins
• Describe the structure and function of lysosomes


  Fluid-filled vesicles surrounded by a single membrane, contain enzymes

  Digests unwanted materials in the cytoplasm
• Describe the structure of centrioles


  Cylindrical structure

  Organised into microtubules in a 9+0 pattern

  Found in pairs in centrosomes
• Describe the function of centrioles


  Migrate to opposite poles of the cell during prophase

  Involved in the organisation of spindle fibres
• Describe the structure of a chloroplast


  Disk shaped surrounded by double membrane

  Thylakoids - flattened discs stacked to form grana

  Grana - contain photosystems with chlorophyll

  Stroma - fluid-filled matrix
• What is the function of a chloroplast?


  Site of photosynthesis
• Describe the structure of the permanent vacuole in plants


  Surrounded by a single membrane

  Contains cell sap (mineral ions, water, enzymes, soluble pigments)
• Describe the function of the permanent vacuole in plants


  Controls turgor pressure

  Water storage

  Isolates harmful waste products

  Maintains pH
• Define plasmodesmata


  Microscopic channels between plant cell walls that facilitate communication and symplastic transport
• Define prokaryotic cell


  A type of cell that does not contain any membrane-bound organelles or a true nucleus
• Describe the structure and function of the flagella in prokaryotic cells


  Long, whip-like protrusion made of flagellin

  Rotates to propel the organism

  Sensory organ
• How is genetic information stored in prokaryotes?


  Plasmids - small rings of DNA that carry non-essential genes

  Loop of DNA - circular DNA stored in the nucleoid region of the cell
• Describe the structure and function of pili in prokaryotic cells


  Hair-like microfibres made of pilin that extend through the cell wall

  Enable the attachment of bacteria to each other and to other surfaces
• Describe the structure and function of the mesosome


  Infolds of the cell membrane

  Increase the surface area of the cell, aiding cellular respiration
• What is the function of the capsule in prokaryotic cells?


  Protective, slimy layer

  Helps the cell to retain moisture and adhere to other surfaces
• Which organelles are found in both eukaryotic and prokaryotic cells?


  Cell membrane

  Cytoplasm with a form of cytoskeleton

  Ribosomes
• Contrast eukaryotic and prokaryotic cells


  Prokaryotic: small, unicellular, eukaryotic: large, often multicellular

  Prokaryotic: no membrane-bound organelles, no nucleus, eukaryotic: contains membrane-bound organelles, true nucleus

  Prokaryotes: 70s ribosomes, eukaryotes: 80s ribosomes
• What is a light microscope?


  A type of microscope that uses a series of lenses and visible light to magnify an image
• What is magnification?


  The number of times bigger an image appears compared to the size of the specimen
• Describe cell theory


  The cell is the fundamental unit of all life forms

  New cells can be formed from existing cells

  Cells contain genetic material which can be transferred to daughter cells
• What is a virus?


  A non-living microorganism that consists of genetic material surrounded by a protein husk
• How do viruses differ from prokaryotic and eukaryotic cells?


  Virus: non-living, pro and eukaryotic: living

  Virus: smaller and simpler in structure, pro and eukaryotic: larger and more complex structure

  Virus: no ribosomes, pro and eukaryotic: contains ribosomes
• Define tissue


  A group of cells working together to carry out a specific function
• Define organ


  A group of tissues working together to carry out a specific function
• Define organ system


  A group of organs that work together to perform a specific function
• What is cuboidal epithelium?


  Small cube-like cells with a prominent nucleus

  Line tubes (kidney tubules)

  Involved in absorption and secretion
• What is ciliated epithelium?


  A layer of cells that have many hair-like extensions called cilia

  Often found in lining oviducts and respiratory passages
• What is striated muscle?


  A muscle that appears banded; also called skeletal muscle.

  It is under the control of the voluntary nervous system