3.2.1.1 Eukaryotic cells

• Leaf structure:

  • Xylem - transports water and dissolved ions
  • Air spaces - Short diffusion path for gas exchange
  • Upper epidermis - transparent for light to penetrate easily
  • Guard cells - control gas exchange and prevents water loss
  • Waxy cuticle - prevent evaporation
  • Spongy mesophyll - Gasses easily accessible for gas exchange
  • Palisade mesophyll - Many chloroplasts
  • Stomata - Allow gas exchange

  
• only animal cells have lysosomes and microvilli

  only plant cells have a cellulose cell wall, a vacuole and chloroplasts

  
• Cellulose cell wall

  Strong to support the plant cell

  Prevents cell from bursting
• Vacuole

  Membrane bound sac of water and dissolved ions

  Helps support the plant cell
• Chloroplasts

  Double membrane bound

  Site of photosynthesis

  Thylakoids/grana - flattened membranes (stack of), providing a larger surface area. Contain embedded molecules

  Stroma - interior containing DNA and ribosomes, starch grains may be present

  
• cell surface membrane

  Phospholipid bilayer with embedded proteins and glycoproteins

  Contains which molecules/ions enter or leave the cell
• Microvilli

  Folded extensions of the cell surface area

  Provides larger surface area of membrane to maximise absorption of molecules/ions
• Nucleus

  Double membrane (nuclear envelope)

  Pores present in the membrane (nuclear pores)

  Stores genetic material organised into chromosomes
• Nucleolus

  Darker stained region in the nucleus

  Makes ribosomes which leave via nuclear pores into the cytoplasm
• Mitochondria

  Double membrane bound - inner highly folded to form cristae - provides large surface area

  Interior of membrane - the matrix

  Has own DNA and ribosomes (can make own proteins)

  Makes ATP in aerobic respiration

  
• Rough endoplasmic reticulum

  Network of flattened membranes (cisternae)

  Has ribosomes embedded on outside

  Lumen inside for transport

  Makes proteins on ribosomes the folds and transports them to the Golgi

  
• Golgi

  A stack of flattened membranes with vesicles around the outside

  Receives vesicles of protein from RER

  Modifies proteins and packages them into vesicles for transporting

  
• Smooth endoplasmic reticulum

  Transports proteins

  Makes, stores and transports lipids

  Makes, stores and transports carbohydrates
• Lysosomes

  Made by Golgi

  Contains lysozyme enzymes

  Used in phagocytosis to digest pathogens
• Vesicles

  Membrane bound sack

  Transports contents from one organelle to another

  e.g proteins from RER --> Golgi --> c.s.m
• Specialised cells


  Sperm cell - many mitochondria, flagellum

  Root hair - microvilli, thin walls, mitochondria

  Nerve cell - Myelin sheath

  Red blood cell - biconcave (large SA), no nucleus (more space for haemoglobin)
• Algal cell

  Cellulose cell wall

  Large chloroplast

  Unicellular
• Fungal cell

  Chitin wall

  Large vacuole

  No chloroplasts

  Some are multicellular, some unicellular