Chapter 1: Cells

• Mitochondria produce energy through aerobic respiration.
• Chloroplasts contain chlorophyll and carry out photosynthesis.
• The nucleus is the control centre of the cell, containing DNA which controls all activities within the cell.
• Light microscope:

  Lower magnification (up to 1000x)

  Lower resolution

  Image is coloured

  Light and smaller, easier to be set-up
• Electron microscope:

  Higher magnification (more than 200,000x)

  Higher resolution

  Image is black and white

  Huge and heavy, difficult to set up
• Protoplasm=cytoplasm+nucleus+cell membrane
• Description of cytoplasm:

  Jelly-like substance that fills the inside of the cell

  Enclosed by the cell membrane

  Contains other cell organelles such as mitochondria

  Part of the protoplasm
• Function of cytoplasm:

  Site for most chemical reactions to occur within the cell
• Description of nucleus:

  • surrounded by membrane called nuclear membrane
  • Contain genetic information in the form of chromosomes
• Functions of nucleus:

  • Controls cell activities such as growth and repair of worn-out parts
  • Is essential for cell division
  • Contains genetic information
• Description of cell membrane:

  • Cell membrane surrounds the cytoplasm of the cell
  • Cell membrane is made up of lipids and proteins
  • It is a partially permeable membrane which means that it only allows certain substances to pass through it
• Function of cell membrane:

  • The cell membrane controls the movement of substances in and out of the cell
• Description of cell wall:

  • Cell wall can only be found in plant cells and not in animal cells
  • Cell wall encloses the entire plant cell, surrounding the cell membrane
  • Made up of cellulose and is fully permeable so it does not control the type of substances entering or leaving the cell
• Functions of cell wall:

  • It protects the cell from injury and gives the plant cell a fixed shape
• Description of ribosomes:

  Small round structures

  2 types of ribosomes:

  • Lie freely in the cytoplasm
  • Attached to the rough endoplasmic reticulum (RER)
• Function of ribosomes:

  To synthesize proteins in the cell
• The ribosomes attached to the RER make proteins that are usually transported out of the cell

  The ribosomes lying freely in the cytoplasm make proteins that are used within the cytoplasm of that cell
• Description of RER:

  • Ribosomes are attached to it's outer surface
  • RER is continuous with the nuclear membrane
• Functions of RER:

  • transports proteins made by ribosomes to the Golgi body for secretion out of the cell
  • Site for protein synthesis
• Description of smooth endoplasmic reticulum (SER):

  • Does not have ribosomes attached to it's membrane
  • SER is more tubular than RER
  • SER is connected to the RER
• Function of smooth endoplasmic reticulum:

  • Synthesises substances such as fats, lipids and steroids
  • Converts harmful substances into harmless substances through a process known as detoxification
• Description of Golgi body :

  • Shaped like a disc
  • Consists of a stack of flattened spaces surrounded by membranes
• Functions of Golgi body:

  • Chemically modifies substances made by the endoplasmic reticulum
  • These modified substances are then stored and packaged in vesicles for secretion out of the cell
• How substances made by the ER are moved out of the cell :

  1. Vesicles transport substances within the cell. Small vesicles containing substances made by the ER are pinched off from the ER
  2. These vesicles then fuse with the Golgi body and release their contents into the Golgi body. The substances made by the ER may be modified inside the Golgi body
  3. Secretory vesicles containing these modified substances are pinched off from the Golgi body. They then move to the cell membrane
  4. The secretory vesicles fuse with the cell membrane and their contents are released out of the cell
• Lipid synthesised from SER are also transported to the Golgi body for modification
• Description of Mitochondria:

  • Mitochondria are small oval or sausage-shaped organelles
  • Mitochondria (plural)
  • Mitochondrion (single)
• Function of mitochondria:

  • A site for aerobic respiration to occur so that food can be broken down to release energy
  • The released energy may be used to carry out cell activities such as growth and reproduction
• Aerobic respiration:

  • Occurs in mitochondria
  • Glucose + oxygen -> carbon dioxide+water+energy
• Anaerobic respiration

  • Occurs in the cytoplasm
• Description of chloroplasts

  • Round -oval structures that are only found in plant cells
  • Chloroplasts contain a green pigment called chlorophyll
  • A cell organelle that will trap sunlight
• Function of chloroplasts:

  • The green pigment found in chloroplasts will trap sunlight from the leaves
  • The sunlight trapped will be used with water and other reactants to undergo photosynthesis
  • Carbon dioxide+ water -> oxygen + food (glucose) [-> is sunlight]
  • Chloroplast also gives the plant it's green colour
• Vacuole:

  • Plant cells have a large central vacuole which stores a liquid called cell sap, which contains dissolved substances such as sugars, mineral salts and amino acids
  • Animal cells have many small vacuoles that contain water and food
• Description of Vacuoles:

  • Fluid-filled space enclosed by a partially permeable membrane
  • Store substances within the cell
  • Membrane - bound cell organelle
  • Animal cells: vacuoles are generally small and help sequester (hide away) waste products
  • Plant cells : vacuoles help maintain water balance. At times can take up most of the interior space of the plant cell
• Functions of Vacuoles:

  • Both plant and animal vacuoles have the same function
  • Store substances within the cell
• Vacuole for plant cells:

  • The central vacuole helps to maintain turgor pressure within the plant cell
  • ***Turgor pressure is the pressure exerted within the cell that presses the cell membrane against the cell wall. This provides structural integrity of the plant cell
• Difference between the vacuoles in animal and plant cell:

  • Plant cells have a large central vacuole whereas animal cells have many small vacuoles
  • Vacuole in plant cells contain a liquid called cell sap while vacuoles in animal cells contain water and food substances
  • Vacuole is permanent in plant cells while in animal cells they usually exist temporarily
• Key differences between plant and animal cells:

  Plants cells:

  • Cell wall present
  • Presence of a large, central vacuole
  • Chloroplasts present

  Animal cell:

  • Cell wall absent
  • Presence of many small vacuoles
  • Chloroplasts absent
• Blood contains red blood cells, white blood cells, platelets and plasma
• Mature red blood cells adaptations to functions:

  Adaptation: Contains haemoglobin (a red pigment)

  Function: Which binds to oxygen and transports it around the body

  Adaptation: Has a circular, biconcave shape

  Function: which increases the surface area-to-volume ratio so that oxygen can diffuse in and out at a higher rate

  Adaptation: lacks a nucleus

  Function: to store more haemoglobin for transport of oxygen

  Adaptation: Is flexible

  Function : can squeeze through capillaries easily
• Muscle cell adaptation to function:

  Adaptation: Is elongated and cylindrical in shape, contains many nuclei and mitochondria

  Function: to pack more in parallel array to increase strength of muscle

  (Insert name): Has mitochondria to release the energy for the contraction of the muscle cell