Investigating Cells

Investigating Cells

Investigating Cells

Interactive Summaries

This is an interactive exercise were you can fill in the correct blanks as you go! The Investigating Cells unit is divided into 4 sub-units:

  • Investigating Living Cells
  • Investigating Diffusion
  • Investigating Enzymes
  • Investigating Cell Division

The first sets of summaries in each sub-unit are all at GENERAL LEVEL!

To select an answer for each blank simply click on the grey box and choose your answer. You can check your answer by using the F1 key.

Investigating Living Cells

What are cells?

  • Cells are the basic units of all
  • A unicellular organism is made up of one cell. For example a
  • A multicellular organism is made up of many cells. For example a cactus plant.
  • When a Biologist wants to observe cells they use a microscope. The Biologist will stain the cells to allow them to see the more clearly.
  • An example of a stain that could be used is

Structures of Animal and Plant Cells

  • The diagram below shows cell.


  • The diagram below shows cell.
  • The structure coloured blue is the , the structure coloured green is the and the structure coloured red is the .

Structure and Functions of Cells

Structure / Function
cell wallnucleuscell membrane / Controls all the cell activities
Cytoplasm / Where all storagechemical reactionsabsorption take place
nucleuscell wallcell membrane / Controls what enters or exits a cell
cell wallcelll membranenucleus / Gives the cell support
Vacuole / Stores energywaterstarch in the cell
Chloroplast / Site of respirationanaerobic respirationphotosynthesis

Summary of Animal and Plant Cells

Structure / Present in animal cell? / Present in plant cell?
Nucleus / presentabsent / presentabsent
Cell membrane / presentabsent / presentabsent
Cytoplasm / presentabsent / presentabsent
Cell wall / presentabsent / presentabsent
Chloroplast / presentabsent / presentabsent
Vacuole / presentabsent / presentabsent

Investigating Diffusion

What is Diffusion?

  • The molecules of a liquid and a move about freely all the time.
  • Diffusion is the movement of a from a region of concentration to a region of concentration until concentrations are.

Diffusion in Cells

  • Diffusion allows substances to enter and exit cells. Substances that would enter a cell by diffusion are and . Substances that would exit a cell by diffusion are and waste.
  • The controls the passage of substance into and out of cells.
  • The is freely permeable to small substances. Large molecules such as are unable to pass through.

Cell membrane


  • Osmosis is the movement of water from a region of water concentration to a region of water concentration across a membrane.

Investigating Enzymes

What is an Enzyme?

  • A chemical that a chemical reaction and yet remains itself unaltered is called a.
  • Anis a biological catalyst and it is made of.
  • Many different enzymes are made by and are present in all.
  • In the absence of enzymes, biological processes such as respiration would proceed at a rate to maintain life.
  • Enzymes are required for the functioning of living cells because they the rate of biochemical reactions to a level high enough to support life.

Breakdown Reactions

  • A breakdown or degradation reaction involves the breakdown of molecules into molecules.
  • A substance in which an enzyme acts on is called the.
  • The substance(s) produced by a reaction is called the product.
  • The table shows examples of breakdown reactions:

substratereactor / Enzyme / Product(s)
Starch / lipaseamylasephosphorylase / simple fatsugarprotein (maltose)
fathydrogen peroxidelactic acid / catalase / carbon dioxidecarbon monoxideoxygenand water
Protein / lipasepepsinphosphorylase / fatty acids and glycerolpeptidesglucose

Build up Reactions

  • A build up or reaction builds up simple molecules into large complex molecules.
  • The reaction below is an example of a build up reaction:

Glucose – 1 – phosphate starch

The Effect of Temperature on Enzyme Activity

  • Enzymes are fairly at low temperatures, but not destroyed.
  • As temperature increases enzyme activity will gradually until an ideal temperature is reached.
  • As temperture increases beyond this ideal temperature, enzyme activity will . This is because at temperatures at or above 50ºC enzymes are normally destroyed or .

The Effect of Different pH Ranges on Enzyme Activity

  • Each enzyme works best at a particular pH.
  • The pH range will depend on the conditions in which it normally operates. For example is suited to the acidic conditions of the stomach which are pH .
  • The working pH range of the enzyme catalse is pH 7-11. It is most active at around . Catalse outside this pH range.
  • Within an ideal pH range of an enzyme its activity will gradually until it reaches its ideal pH. After this point the enzyme activity will .

Investigating Cell Division

What is cell division?

  • Cell division is the means by an organism its number of cells.
  • In a unicellular organism cell division is a form of , making two new individuals.
  • In a multicellular organism cell division results in growth of the original organism.

  • is the biological term for cell division.
  • In this process the nucleus divides into two nuceli each of which have exactly the same number of as were present in the original nucleus.
  • The following diagram below shows the six main stages of mitosis:
  • Stage (a) & (b) The nucleus contianing uncoiled chromosomes each to form two identical chromatids.
  • Stage (c) The chromosomes become and more visible. membrane disappears.
  • Stage (d) The chromosomes line up along the of the cell. Spindle fibres form amd each choromsome becomes attached by its .
  • Stage (e) Pair of identical chromatids separate and move to opposite of the cell.
  • Shage (f) Seperated chromatids now called . New Nuclear membrane will form. divides to form two identical cells containing the same number of chromosomes as the original cell.

This is the end of the General section. Well done!!

Take note of sections you found difficult and remember to ask your Biology teacher for help!

Now try the Credit section of Investigating Cells!