Biology, 2: Cells

• Cells contain different structures to help them fulfill their roles
• Animals and plant cells:

  
• Animal cells contain…

  • Nucleus
  • Cytoplasm
  • Cell membrane
  • Mitochondria
• Plant cells contain…

  • Nucleus
  • Cytoplasm
  • Cell membrane
  • Mitochondria
  • Cell wall
  • Chloroplasts
  • Vacuole
• What is the function of the cell membrane?

  Holds cell together

  Controls substances entering and leaving the cell
• What is the function of the cytoplasm?

  Supports small cell structures

  Where chemical processes occur

  Contains water and dissolved solutes
• What is the function of the nucleus?

  Contains genetic material in chromosomes

  Controls how cell grows and works

  Controls cell division
• What is the function of the cell wall?

  Made of cellulose

  Gives cell extra support

  Defines cell shape
• What is the function of the vacuole?

  Contains cell sap

  Used for storage of materials

  Supports cell wall

  If there is not enough cell sap in vacuole, plant may wilt
• What is the function of the chloroplasts?

  Contains chlorophyll (green pigment)

  Absorbs light energy needed for photosynthesis
• Specialized cells are cells that have a specific function and are adapted to perform that function.
• What are the specialized cells?

  • Ciliated cells
  • Root hair cells
  • Palisade mesophyll cells
  • Red blood cells
  • Sex cells
• Ciliates cells keep the lungs clean and are adapted for movement of mucus in the trachea and bronchi.
• What is the cilia and its functions?

  Tiny hair-like projection covering certain cells

  Can be moved by cells co-ordinating movement

  Allows cilia to move liquid in particular direction
• What is the ciliated epithelial cells and its functions?

  It is in the lining of the respiratory tract

  Moves mucus and the dust and bacteria in it

  Emptied in oesophagus, swallowed in the stomach
• Ciliated cells:

  
• What is the root hair cells and its functions?


  Adapted for absorption

  Is elongated, increasing surface area available to absorb water and mineral ions

  Becomes waterproof with time, not functioning after

  New ones grow constantly
• What is the palisade mesophyll cells and it’s functions?

  Adapted for photosynthesis

  Contains large numbers of chloroplasts

  Found in the upper part of the leaf
• What is the red blood cell and it’s function?

  Adapted for transport of oxygen

  No nucleus, more space

  Full of haemoglobin, picks up O2

  Biconcave shape allows for rapid diffusion

  Made in the bone marrow

  Contains: RBC, WBC, plasma, platelets
• Composition of blood

  
• What does the RBC do?

  Carries O2
• What does the WBC do?

  Produces antibodies

  Ingests pathogens (phagocytosis)
• What does the plasma do?

  Transports CO2, digested food molecules, urea, and hormones

  Distributes heats
• What does the platelets do?

  Clots blood
• What is the sperm and its function?

  Adapted for reproduction

  Contains very little cytoplasm around the nucleus

  Acrosomes digest hole in the egg membrane so sperm can enter and fuse

  Mitochondria provides energy to move flagellum
• What is the egg cells and it’s functions?


  Large

  Cannot move on its own

  Large amount of cytoplasm to provide nutrient when cell is fertilised

  Jelly coat hardens after sperm fertlisies
• Magnification formula

  
• Diffusion is the net movement of particles from a region of higher concentration to a region of lower concentration down a concentration gradient as a result of their random movement
• What is diffusion influenced by?

  Surface area, temperature, concentration gradient, diffusion distance
• Osmosis is the net movement of water molecules from a region of higher w.p (dilute) to a region of lower w.p (concentrated), through a partially permeable membrane
• Water potential is the ability to draw water into itself. This decreases as more solutes are added.
• Turgid cells are full of water.

  There is turgor pressure, due to the pressure of water in cytoplasm against the cell wall.

  This prevents more water from entering.
• Plasmolysed cells are dehydrated.

  The cytoplasm shrinks, leaving a gap between the cell wall and membrane.

  It is flaccid.
• Water molecules move into the root hair cell, across the cells of roots down a w.p gradient.

  The w.p gradient is maintained as xylem vessel removes water from root due to transpiration from leaves.
• Animal cells can also gain/lose water, however effects are more dramatic due to absence of cell wall.
• If animal cell is lowered into a solution with lower w.p, it loses water.

  It becomes crenated.
• If animal cell is lowered into a solution with higher w.p, it gains water.

  It swells and bursts (lyse).