Eukaryotes + Prokaryotes : Cells

• Eukaryotes


  Cells that have a nucleus
• Prokaryotes


  Cells that do not have a nucleus
• Both animal and plant cells are eukaryotes
• Eukaryotic cells contain their genetic material enclosed in a nucleus
• Bacteria are prokaryotes
• Prokaryotic cells have their genetic material not enclosed in a nucleus
• Prokaryotic cells


  • Smaller than eukaryotic cells
  • Genetic material is a single loop of DNA
  • May also have small rings of DNA called plasmids
  • Have a cell wall, but not like a plant cell wall
• Cell types


  • Eukaryotic
  • Prokaryotic
• Cytoplasm


  Watery solution where chemical reactions take place
• Cell membrane


  Controls the molecules that can enter and leave the cell
• Mitochondria


  Where aerobic respiration takes place
• Ribosomes


  Site of protein synthesis
• Plant cells


  • Have a regular shape
  • Have common organelles with animal cells: nucleus, cytoplasm, cell membrane, mitochondria, ribosomes
• Chloroplasts


  Contain chlorophyll and are the sites of photosynthesis
• Cell wall


  Made from cellulose, strengthens the cell
• Vacuole


  Filled with cell sap, helps give the plant cell its shape (rectangular)
• Animal cells


  • Most are specialised
  • Have adaptations which help to carry out a specific function
• Differentiation


  When cells become specialised
• Fertilisation


  The process where the genetic information of the ovum and the sperm combine
• Sperm cell


  • Has a long tail which allows it to swim to the ovum
  • Is streamlined to make swimming easier
  • Is packed full of mitochondria to provide the energy needed for swimming
  • Contains enzymes which allow it to digest its way through to the ovum
  • Contains only half the genetic information of a normal adult cell
• Nerve cell


  • The axon carries electrical impulses from one part to another
  • Myelin insulates the axon and speeds the transmission
  • The end of the axon has synapses which allow the impulse to pass from one nerve cell to another
  • Dendrites increase the surface area so that other nerve cells can connect easily
• Muscle cell


  • Contains protein fibres which can change their lengths
  • When a muscle cell contracts, these fibres shorten, decreasing the length of the cell
  • Is packed full of mitochondria to provide energy for muscle contraction
• Plant cell specialisation


  Most plant cells are specialised and have special adaptations which help them to carry out their function
• Differentiation


  The process by which plant cells become specialised
• Root hair cells


  • Increase the surface area so they can absorb water and minerals more effectively
  • Do not contain chloroplasts as they are underground
• Xylem


  • Found in the plant stem
  • Form long tubes that carry water and minerals from the roots to the leaves
  • Have very thick walls containing lignin to provide support
  • Have cell walls sealed with lignin, causing the cells to die
  • Have end walls that have broken down, forming a long tube for easy flow of water and minerals
  • Have no nucleus, cytoplasm, vacuole or chloroplasts, making it easier for water and minerals to flow
• Phloem


  • Carry dissolved sugars up and down the plant
  • Consist of two cell types: phloem vessel cells and companion cells
  • Phloem vessel cells have no nucleus and limited cytoplasm
  • Phloem vessel cells have pores called sieve plates in their end walls, allowing dissolved sugars to move through
  • Companion cells are connected to the vessel cells by pores and provide them with energy from their mitochondria
• The nucleus is the control center of the cell.
• Ribosomes make proteins.
• Vacuoles store food and waste products.
• Chloroplasts convert sunlight into sugar.
• Chloroplasts produce food (glucose) through photosynthesis.
• Mitochondria produce ATP (energy) through respiration.
• Mitosis


  The process of cell division in which a single cell divides into two or more daughter cells
• Chromosomes


  • Found in the nucleus
  • Made of the molecule DNA
  • Body cells contain 23 pairs
  • Gametes have 23 single chromosomes
  • Carry a large number of genes which determine many of our features
• Cell cycle


  1. DNA replicates to form two copies of each chromosome

  2. Cell grows and copies its internal structures (organelles)

  3. Mitosis takes place

  4. Nucleus divides

  5. Cytoplasm and cell membrane divide to form two identical cells
• Mitosis


  • Essential for growth and repair
  • Occurs during asexual reproduction
  • Occurs when an organism repairs itself
• Fertilisation


  When a sperm cell joins with an egg cell
• Embryo development


  1. Fertilised ovum undergoes mitosis

  2. Cells continue to undergo mitosis

  3. Cells change and begin to form specialised cells through differentiation
• Stem cells


  Undifferentiated cells which can differentiate to form other types of cells