Download Revision summary 2. Movement, Molecules and Enzymes File

Revision notes 2: biological molecules, movement of substances into / out of cells, enzymes
BIOLOGICAL MOLECULES AND ENZYMES
2.5
Recall the chemical elements present in carbohydrates, proteins and lipids (fats and
oils)
Carbohydrates and lipids: C,H,O;
Proteins also have nitrogen so their elements are C,H,O,N
2.6
C = carbon, H = hydrogen,
O = oxygen; N = nitrogen
Describe the structure of carbohydrates, proteins and lipids as large molecules
made up from smaller basic units:
starch and glycogen from simple sugar (glucose); protein from amino acids; lipid from fatty
acids and glycerol
2.7
Describe the tests for glucose and starch
Glucose: Benedict's
solution, heated
Colour of solution changes from blue through green and
yellow to brick red if glucose is present.
Starch: Iodine
solution
Colour change from yellow-brown to blue-black if starch is
present
2.8
Understand the role of enzymes as biological catalysts in metabolic reactions (there
is more about specific enzymes in the notes about nutrition and digestion)
2.9
Understand how the functioning of enzymes can be affected by changes in
temperature
All enzymes have an optimum temperature where they work fastest
Low temperatures: less kinetic energy means fewer collisions between enzyme
and substrate
High temperature: the enzyme is denatured (changes shape making the enzyme
inactive)
2.1
Understand how the functioning of enzymes can be affected by changes in pH
All enzymes have an optimum pH where they work fastest
At high or low pH, the enzyme is denatured so is inactive or less active
2.11
Describe how to carry out simple controlled experiments to illustrate how enzyme
activity can be affected by changes in temperature
The experiment in the syllabus is using amylase to break down starch.
Iodine (on a spotting tile) is used to test whether starch is still present (see point2.70),
The amylase / starch mixture is tested at different temperatures, e.g. 20°C, 30°C, 40°C,
50°C
Revision notes 2: biological molecules, movement of substances into / out of cells, enzymes
D) MOVEMENT OF SUBSTANCES INTO AND OUT OF CELLS
2.12
2.13
recall simple definitions of diffusion, osmosis and active transport
understand that movement of substances into and out of cells can be by diffusion,
osmosis and active transport
Diffusion: Movement of particles from a region of higher concentration to a region of lower
concentration. It is passive – it does not need energy from respiration as it depends on the
movement energy of the particles themselves (their kinetic energy)
Osmosis: net movement of water molecules from an area of higher water concentration
(water potential) to an area of lower water concentration (or water potential) across a
semi-permeable membrane
Alternatively, osmosis can be described as the net movement of water molecules from a
more dilute (or hypotonic) solution to a more concentrated (hypertonic) solution across a
semi-permeable membrane.
Active transport: movement of particles from a region of lower concentration to a region of
higher concentration using energy from respiration
Can also be described as movement against the concentration gradient (whereas
passive diffusion moves substances down their concentration gradient)
2.14
understand the importance in plants of turgid cells as a means of support
The vacuole fills with water and puts pressure on the cytoplasm,
which presses against the cell wall and makes the cell turgid
(stiff)
2.15
understand the factors that affect the rate of movement of
substances into and out of cells
the rate of movement of substances increases when the



surface area to volume ratio is high,
temperature is high, and
concentration gradient is steep (big difference in concentration)
the distance that a substance has to move is also important in root hair cells (see point
2.53), in the small intestine (see point 2.31), and in gas exchange between the alveoli and
capillaries ( 2.46)
2.16
describe simple experiments on diffusion and osmosis using living and non-living
systems.
Diffusion: Absorption of coloured substances by cubes of agar
gel (small cubes => fast diffusion as SA:Volume ratio is higher)
Osmosis: Potato stick experiment (increased mass when in
distilled water)
Factors investigated:
SA:Volume ratio, temperature;
concentration gradient
Revision notes 2: biological molecules, movement of substances into / out of cells, enzymes
D) ENZYMES AND POLYMERS
2.5
Recall the chemical elements present in carbohydrates, proteins and lipids (fats and
oils) 
2.6
Describe the structure of carbohydrates, proteins and lipids as large molecules
made up from smaller basic units: 
2.7
Describe the tests for glucose and starch 
2.8
Understand the role of enzymes as biological catalysts in metabolic reactions 
2.9
Understand how the functioning of enzymes can be affected by changes in temperature 
2.1
Understand how the functioning of enzymes can be affected by changes in pH 
2.11
Describe how to carry out simple controlled experiments to illustrate how enzyme activity
can be affected by changes in temperature 
D) MOVEMENT OF SUBSTANCES INTO AND OUT OF CELLS
2.12
recall simple definitions of diffusion, osmosis and active transport 
2.13
understand that movement of substances into and out of cells can be by diffusion, osmosis
and active transport 
2.14
understand the importance in plants of turgid cells as a means of support 
2.15
understand the factors that affect the rate of movement of substances into and out of cells

2.16
describe simple experiments on diffusion and osmosis using living and non-living systems. 