Cells

• What are the smallest building blocks for living organisms?

  Cells
• What are organisms which are made of only one cell called?

  Unicellular organisms
• What are organism which are made up of millions of cells called?

  Multicellular organisms
• The living materials of an animal cell.

  Protoplasm
• Protoplasm of animal cells:

  Cell membrane

  Cytoplasm

  Ribosomes

  Mitochondria

  Nucleus
• What is protoplasm?

  The living materials of an animal cell
• The boundary enclosing the protoplasm; made up of fats and proteins. Contains small pores to allow small molecules to pass through (selectively permeable).


  Cell membrane
• Functions of cell membrane:

  • controls the entry and exit of substances into and out of the cell
  • prevents leakage of cytoplasm
  • gives shape to the cell
• A jelly like substance made up of 80% water and 20% dissolved substances.


  Cytoplasm
• Function of cytoplasm

  The site for chemical reactions
• Cytoplasm contains structures called -

  Organelles
• The largest organelle in a cell surrounded by nuclear membrane and contains nucleolus and thread like structures called chromosomes.


  Nucleus
• Made up of DNA twisted around proteins (histones)


  Chromosomes
• Functions of the nucleus:

  • It controls the activity taking place in the cell
  • The chromosomes determines the characteristics of an organism
  • Important for cell division
• Rod shaped or circular structure found in the cytoplasm; surrounded by a double membrane and contain circular DNA and many ribosomes.


  Mitochondria
• Functions of mitochondria:

  • the site for aerobic respiration
  • produces energy which is stores in the for of adenosine triphosphate, ATP
• The smallest organelle in the cytoplasm divided into two sub units; large subunit and small subunit. Present in mitochondria and chloroplasts.


  Ribosome
• made up of cellulose which is hard and rigid and porous (fully permeable)


  Cell wall
• Functions of cell wall:

  • Provides mechanical support to the plant cell and allows the cell to become turgid
  • Gives a definite shape to the cell
  • prevents the cell from bursting when water enters it.
• Small organelles containing green pigment called chlorophyll.


  Chloroplast
• Functions of chloroplast:

  • Chlorophyll absorbs light which is used in photosynthesis.
  • Stores starch which is food for animals and plants
• A fluid filled sac enclosed by a partially permeable membrane called the tonoplast; its content is the cell sap


  Large central vacuole
• Functions of large central vacuole:

  • Acts as a store of food
  • provides turgor pressure to support the cell
  • Stores waste product to be removed from the cell.
• Single celled microorganism which doesn't contain a nucleus.

  Bacteria
• Protoplasm of bacteria:

  • Plasmid
  • Cell wall
  • cell membrane
  • cytoplasm
  • circular DNA
  • Ribosome
• Red blood cell is a specialised cell which carries oxygen throughout the body
• Adaptation of red blood cells:

  • It has a biconcave shape to increase its surface area for rapid diffusion of oxygen.
  • Contains red pigment called haemoglobin which combines with oxygen to form oxyhaemoglobin.
  • It doesn't have a nucleus to provide space for packing more haemoglobin.
• The nerve cell transmits nerve impulses and helps in the coordination of different body parts.
• Adaptations of Nerve cell:

  • It has an elongated body to transmit impulses.
  • It has gaps for rapid transmission of impulses.
• The sperm cell is a male gamete; it carries genetic information and is specialised for fertilisation.
• Adaptation of sperm cell:

  • It has a tail which helps it swim into the uterus.
  • It is small and light produced in large amount to increase the chance of fertilisation.
• An egg cell is bigger than sperm cell; contains yolk, a store of energy. And the genes of the mother is found in the nucleus of the cell.
• Ciliated cells are found in air passages of the lungs and oviducts; they have cilia on their surfaces.
• Adaptations of ciliated cells:

  • in airways, cilia moves the mucus that traps pathogens and dust up to the nose and throat.
  • In oviducts, cilia move the eggs to the uterus.
• Root hair cells absorb water and mineral ions from the soil; they are found in large amount to provide anchorage to the plant.
• Adaptation of root hair cells:

  • Has a long extension which increases surface area for rapid absorption of water and minerals.
  • Its vacuole is concentrated to absorb water by osmosis.
• Xylem vessel is a cylindrical tube found in plant that transports mineral ions and water from the root to all parts of the plant. And provide support to the plant.
• Adaptation of xylem vessels:

  • The wall is strengthen by a deposit of waterproof material call lignin which supports the plant.
  • They have hollow tube which allows continuous flow of water.
  • They have no end wall that interrupts the flow of water.
• Palisade mesophyll cell is a long cylindrical cell with numerous chloroplast in its cytoplasm; it absorbs light for photosynthesis.
• Adaptations of palisade mesophyll cell:

  • Contains numerous chloroplasts to maximise absorption of light.
  • They have large vacuole which pushes the chloroplast towards the top to absorb sunlight.
  • Its walls have tough cellulose which strengthen the cell.