Cells

• What are the distinguishing features of eukaryotic cells?

  • Cytoplasm containing membrane-bound organelles
  • so DNA enclosed in nucleus
• What’s the general structure of eukaryotic cells?

  • Cell surface membrane
  • mitochondrion
  • nucleus
  • ribosomes
  • rough endoplasmic reticulum
  • smooth endoplasmic reticulum
  • Golgi apparatus
  • lysosome

  
• What’s the structure of the cell-surface membrane?

  Phospholipid bilayer made up of:

  • Hydrophilic phosphate heads point outwards as attracted to water
  • Hydrophobic fatty acid tails point inwards as repel from water
  • protein transport systems
• What’s the function of the cell surface membrane?

  • Selectively permeable -> enables control of passage of substance in and out of cell
  • Molecules/receptors/antigens on surface -> allow cell recognitions
• Whats the structure of the nucleus?

  • Nuclear envelope (double membrane and has nuclear pores)
  • Nucleoplasm
  • Nucleolus (dense region)
  • Protein/histone bound linear DNA (chromatin = condensed and chromosome = highly condensed)
• What’s the function of the nucleus?

  Holds and stored genetic information which codes for polypeptides

  Site of DNA replication

  Site of transcription producing mRNA

  Nucleolus makes ribosomes/ rRNA
• What’s the structure of a ribosome?

  made of rRNA and protein

  not a membrane bound organelle
• What’s the function of a ribosome?

  site of protein synthesis (translation)
• Describe the structure of rough endoplasmic reticulum and smooth endoplasmic reticulum.

  rER

  • ribosomes on surface synthesise proteins
  • proteins processed inside rER
  • proteins packaged into vesicles for transport e.g. Golgi apparatus

  sER

  • synthesises and processes lipids
  • E.g. Cholesterol and steroid hormones
• What’s the structure of Golgi apparatus and Golgi vesicles?

  Apparatus = flattened membrane sacs

  Vesicles = small membrane sac
• What’s the function of Golgi apparatus and golgi vesicle?

  Apparatus

  • modifies protein
  • modifies lipids
  • packages proteins and lipids into vesicles
  • produces lysosome

  Vesicles

  • transports proteins and Lipids to their destination
  • E.g. Moves to and fuses with cell surface membrane
• whats the structure of lysosomes

  1. membrane
  2. hydrolytic enzymes

  
• What’s the function of lysosomes


  Release hydrolytic enzymes to break down/hydrolyse pathogens or worn out cell components
• What’s the structure of mitochondria?

  Outer membrane, Cristae - inner membrane fold and matrix which contains small ribosomes and circular DNA

  
• What’s the function of mitochondria?

  The site of aerobic respiration to produce ATP for energy release for example protein sysnthesis
• What’s the structure of chloroplasts?


  Double membrane, stroma, lamella, grana

  
• What’s the function of chloroplasts?


  absorbs light energy for photosynthesis to produce organic substances eg carbohydrates and lipids
• Describe the structure of cell wall in plants, algae and fungi

  Mainly cellulose in plants/algae but composed of chitin in fungi
• What’s the function of the cell wall in plants algae and fungi?

  Provide mechanical strength to the cell so prevents it changing shape or bursting under pressure due to osmosis
• What’s the structure of the vacuole in plants?

  Tonoplast membrane and cell sap

  
• What’s the function of the vacuole in plants?

  Maintains turgor pressure in cell and contains cells sap which stores sugars, amino acids and any waste chemicals
• How are eukaryotic cells organised in complex multicellular organisms

  Tissues - group of specialised cells with a similar structure working together to perform a specific function, often with the same origin

  Organ - aggregations of tissues performing specific functions

  Organ System - group of organs working together to perform a specific function
• What are the distinguishing features of prokaryotic cells?

  Cytoplasm lacking membrane bound organelles so genetic material not enclosed in nucleus
• What’s the general structure of prokaryotic cells?

  ALWAYS PRESENT:

  • Cell surface membrane
  • cell wall
  • cytoplasm
  • small ribosomes
  • circular DNA

  SOMETIMES PRESENT:

  • Capsule
  • Plasmids
  • Flagella

  
• Differences in Eukaryotic cells and Prokaryotic cells:

  Eukaryotic Cells:

  • has membrane bound organelles
  • has a nucleus
  • DNA is long
  • larger ribosomes
  • cell wall contains cellulose or chitin
  • plasmids and capsule never present
  • larger overall size

  Prokaryotic cells

  • no membrane bound organelles
  • no nucleus
  • DNA is short and circular
  • smaller ribosomes
  • cell wall contains murein (glycoprotein)
  • plasmids flagella and capsule sometimes present
  • smaller overall size
• What are viruses described as?

  Acellular and non-living
• What’s acellular?


  Not made of cells, no membrane/cytoplasm/organelles
• What’s non-living?


  Have no metabolism, cannot independently move/respire/replicate/excrete
• What’s the general structure of a virus?

  • Nucleic. Acids surrounded by capsid
  • attachment proteins allow attachment to specific host
  • no cytoplasm, ribosomes, cell wall
  • some also surrounds by a lipid envelope

  
• What’s magnification 


  The number of times greater image is than size of object
• What’s resolution?


  Minimum distance apart 2 objects can be to be distinguished as separate objects
• The different microscopes?


  Optical, Transmissoon, Scanning

  
• Magnification formula


  …

  
• Units convertions

  
• Describe how the size of an object viewed with an optical microscope can be measure

  1. line up eyepiece with stage micrometer
  2. calibrate eyepiece graticule
  3. take micrometer away and use graticule to measure how many divisions make up the object
  4. calculate size of object by multiplying number of division by size of division
  5. recalibrate eyepiece graticule At different magnifications
• Principles of cell fractionation to separate cell components:

  1. homogenise tissue - disrupts cell membrane breaking open cell and releasing contents
  2. place in cold isotonic buffered solution - cold reduces enzyme activity so not broken down. isotonic so water doesn’t move via osmosis. buffered to keep pH constant so enzymes don’t denature
  3. filter homogenise- remove large unwanted debris
  4. ultracentrifugation - seperate organelles in order of density. Nuclei-chloroplast/mitochondria- lysosomes-ER - ribosomes
• What happens during interphase 


  DNA replicates semi conservatively leading to 2 chromatids joined at centromere and number of organelles and vol of cytoplasm increases
• What happens during mitosis

  Nucleus divide to produce 2 nuclei which are genetically identical
• What happens during cytokinesis

  Cytoplasm and cell membrane divide to form 2 new genetically identical daughter cells
• What happens during Prophase 1

  • Chromosomes condense becoming shorter and thicker and appear as 2 sister chromatids joined by a centromere
  • nuclear envelope breaks down
  • centrioles love to opposite poles forming spindle metwork