BIO Topic 1: Cells

• What is a cell?

  the basic unit of life
• Cells are too small to be seen using naked eyes. Hence, we use a light or electron microscope to see the cells' structures.
• What makes up the protoplasm(living structures) of a cell?


  cell membrane, cytoplasm and nucleus
• Cells can exist as unicellular or multicellular.
• examples of unicellular cells(singe cell)


  amoeba, bacteria, paramecium
• examples of multicellular cells (more than 1 cell)


  red blood cells, root hair cells, muscle cells
• Bacterium cell

  
• Difference between prokaryotic cells and eukaryotic cells

  • Genetic material in eukaryotic cell has a nuclear membrane surrounding it while genetic material in prokaryotic cell lies freely in the cytoplasm.
  • Prokaryotes are always unicellular, while eukaryotes are often multicellular
• Features of cell membrane

  • partially permeable (allows only some substance to pass through it)
  • made up of proteins and lipids
• Function of cell membrane

  Controls small substances from entering and leaving the cell
• Features of cytoplasm

  Contains mainly water, food substances and chemical compounds, and specialized organelles laying on it
• Functions of cytoplasm

  it is where chemical reactions of the cell take place
• Features of nucleus

  • consists of nucleolus, nucleoplasm and chromatin which is surrounded by a nuclear membrane
  • nuclear membrane is partially permeable
  • chromatin is made up of proteins and linear DNA
  • heredity information is stored in the DNA and is passed from one generation to another
  • DNA carries instructions that a cell needs to carry out is activities
• Function of nucleus

  1. controls all cell activities (cell growth / repairing of tissues)
  2. helps in cell division
• Features of mitochondria

  • rod shaped organelles
  • can only be seen under electron microscope
• Functions of mitochondria

  Releases energy from food substances through aerobic respiration
• Features of cell wall

  • non living structure
  • surrounds the cell membrane
  • made of cellulose
  • fully permeable
• Functions of cell wall

  Protects, supports and maintains the shape of the cell
• Features of large central sap vacuole

  • contains sap solution/cell sap (solution made up of mostly sugars and other substances)
  • enclosed by a partially permeable membrane(tonoplast)
  • small and temporary (in animal cells)
  • large and permanent (in plant cells)
• Functions of sap vacuoles

  • stores food and water
  • maintains turgidity of plant cells by osmosis
• Features of chloroplast

  • smaller than nucleus
  • contains chlorophyll (green pigments which make the leaves green)
• Functions of chloroplast

  chlorophyll found in chloroplast absorbs light energy for photosynthesis
• Functions of pili

  helps bacteria to adhere / grab on to surfaces
• Functions of capsule

  • protects bacteria from being digested by white blood cells
  • outermost layer of bacterium cell
• Features of ribosomes

  small and round structures
• Functions of ribosomes

  synthesizes proteins in cell
• features of plasmid

  • small circular double rounded DNA molecules
• functions of plasmid

  • genes carried provide bacteria with genetic advantages such as antibiotic resistance
  • used as a foreign vector to introduce a foreign DNA into bacteria in biotechnology
• Features of flagellum

  whip like structure
• Functions of flagellum

  helps in movement
• Animal cells VS Plant cells

  Plant cells contain chloroplasts, a cell wall and a large central sap vacuole but animal cells do not.

  
• Function of Root hair cell

  Absorbs water and mineral salts from the soil
• Function of erythrocytes (red blood cell)

  to transport oxygen from the lungs to respiring body tissues
• Functions of xylem vessels

  1. transport water and mineral salts from roots to all part of the plant
  2. provide mechanical support for the plant
• Root hair cell (Adaptation + function related)

  1. long and narrow - increases the surface area to allow rapid absorption of mineral salts and water
  2. has a large vacuole more concentrated than the soil - creates a concentration gradient which allows it to absorb as much water as it can
• Erythrocytes (Adaptation + function related)

  1. contains haemoglobin - enables red blood cell to carry oxygen(forming oxyhaemoglobin) to be transported to the body tissues
  2. no nucleus - cytoplasm can carry more haemoglobin so more oxygen can be carried
  3. has a biconcave shape - provides a larger surface area for rapid oxygen absorption
• Xylem vessels (Adaptation + function related)

  1. long, hollow and narrow with continuous lumen - allows the transport of water and mineral salts up the plant
  2. walls thickened by lignin - helps to strengthen wall & prevents the collapse of the vessel
  3. no protoplasm - water can flow easily without disruption
  4. present in bundles - provides mechanical support for the plant
• What is a tissue?

  a group of similar cells working together to perform a specific function
• What is an organ?

  A group of tissues that work together to perform a specific function.
• What is an organ system?

  An organ system is a group of organs that work together to perform a specific function.