B1

• All living things are made of cells, which can either be prokaryotic or eukaryotic.
• Prokaryotic cells are small and have DNA out in the cytoplasm and example is bacteria. The structure of the cell is simple.
• Eukaryotic cells are large and have DNA in the nucleus. Some examples are animal, plant and fungi. The structure of the cell is complex.
• deci-0.1 of a meter (10^-1)

  centi- 0.01 of a meter (10^-2)

  milli- 0.001 of a meter (10^-3)

  micro- 0.000,001 of a meter (10^-4)

  nano- 0.000,000,001 of a meter (10^-5)
• Organelles in an animal cell


  • Nucleus
  • Cytoplasm
  • Mitochondria
  • Ribosome
  • Cell membrane
• Organelles in a plant cell


  • Mitochondria
  • Cytoplasm
  • Vacuole
  • Cell wall
  • Cell membrane
  • Ribosome
  • Chloroplasts
  • Nucleus
• Organelles in a bacterial cell


  • Cytoplasm
  • Cell membrane
  • Cell wall
  • Single circular strand of DNA
  • Plasmids
• Describe the differences between a prokaryotic and a eukaryotic cell

  1. A prokaryotic cell does not have a nucleus, but a eukaryotic does
  2. A prokaryotic cell is smaller than a eukaryotic one
  3. A prokaryotic cell does not have a mitochondria
  4. Prokaryotic cells have plasmids and eukaryotic cells do not
• Describe the differences and similarities between a prokaryotic cell and a plant cell

  1. Both have a cell wall
  2. Both have cytoplasm, cell membrane and ribosomes
  3. Plant cells have vacuole and chloroplast but prokaryotic ones do not
• Nucleus


  Contains genetic information (DNA)
• Cell membrane


  Controls what enters and leaves the cell
• Cytoplasm


  A gel like substance where most chemical reactions occur, contains enzymes and organelles are found in it
• Mitochondria


  Where aerobic respiration reactions occur providing energy for the cell
• Ribosomes

  Where protein synthesis occurs
• Vacuole


  Contains sap (a weak solution of sugar and salt)to help keep the cell turgid
• Cell wall


  Rigid structure made from cellulose it supports and strengthen the cell
• Chloroplast


  Contains chlorophyll which absorbs light energy needed for photosynthesis
• Sperm cells function is to fertilise the female egg cell

  1. It contains lots of mitochondria to release energy from respiration to allow the sperm to swim to the egg
  2. The head contains enzymes to allow the sperm to break through the membrane of the egg cell
  3. The head contains DNA from the father
• Nerve cells are used to carry information from one part of the body to another

  1. It has lots of mitochondria
  2. Nerve fibres to carry electrical impulses
• Muscle cells are used to produce movement by contracting

  1. They contain lots of mitochondria to release energy from respiration for contracting and relaxing muscles
• The root hair cells absorb water and minerals from the soil

  1. They have lots of hairs for a large surface area for absorbing water and minerals
  2. Thin hair which have thin walls to allow a short diffusion pathway
  3. Lots of mitochondria for active transport
• Xylem cells are used to transport water and minerals up the plant from the roots to the shoots

  1. they are arranged and to end to form a continuous tube so water and mineral irons can move through
• Phloem cells are used to carry the products photosynthesis to all parts of the plant

  1. End wall of cells like a sieve to allow sugar through
  2. Cells arranged end to end
• A cell is the basic unit that organisms are made up of
• A tissue is a group of similar cells that work together to carry out a specific function
• An organ is a group of different tissues that work together to carry out a specific function
• An organ system is a group of organs working together to perform a specific function
• Magnification is the number of times bigger the image size is compared to the real size
• resolution is the ability to distinguish between two points
• Give two advantages of the electron microscope over the light microscope

  • Higher resolution to see organelles in more detail
  • Higher magnification
• Light microscope has a magnification of X 2000. It has a resolution of 200 nm. It uses mirrors and light to create an image. It is portable ,relatively cheap and produces a coloured image and is used to see living and dead biological material.
• Electron microscope has a magnification of X2,000,000. it has a resolution of 0.2 nm and uses electrons to create the image. it is very large and fixed. It is expensive and produces a black-and-white image and it can be used to only view dead biological material
• Light microscope

  
• Total magnification = magnification of objective lens x magnification of eyepiece lens
• Microscopy practical

  1. Peel a thin layer of tissue, it has to be thin enough to allow light to pass through
  2. Tissue on glass slide and add two drops of iodine the iodine will stay in the cell so we can see the structures and organelles
  3. Place the covers slip on the slide using a mounting needle place at an angle to avoid air bubbles
  4. View under the microscope start with the lowest objective lens then focus
• Viewing through a microscope

  1. Change the objective lens to the lowest magnification e.g X4
  2. Use the course wheel to bring the slide up to focus
  3. Use the fine focus to make the image clearer
  4. Change the objective lens to a higher one to view image
• Magnification = image size/actual size
• Cell cycle

  1. Cell is not dividing-the cell grows and increases the number of organelles (e.g mitochondria, ribosome) ready for cell division
  2. MITOSI-The cell duplicates it’s DNA DNA is copied and forms X shaped chromosomes
  3. The chromosomes, then lineup at the centre of the cell cell fibres pull them apart opposite ends of the cell
  4. Nuclei divide into two
  5. Cytoplasm and cell membrane divide into two. The number of chromosomes at each end of the cell are identical to the parent cell.
• Importance of mitosis

  • For growth
  • Repair and replacement
  • Asexual reproduction
• Mitosis is when a cell divides and splits to form two genetically identical daughter cells which have the same number of chromosomes and are identical to the parent cell