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Biology 12 Cells and the environment
Cells exchange matter and energy
In: Out:
Cells exchange matter and energy
In:
Oxygen
Nutrients eg glucose
(carbon dioxide and light energy in plants)
Water
Ions
Out:
Carbon dioxide
Wastes eg urea
(oxygen in plants)
Water
Ions
Heat energy
Processes:
Respiration
Synthesis
Growth
Division
Photosynthesis (in plants)
Responding to the environment
• Internal environment = cell cytoplasm• External environment –Unicellular organisms Multicellular
organisms
Responding to the environment
• Internal environment = cell cytoplasm• External environment – Unicellular organisms Multicellular organisms
Outside world blood, intercellular fluid
Unicellular responses to the environment 1
• Engelmann’s experiment
Unicellular responses to the environment 1• Engelmann’s experiment
Light split by lens
Alga growing under split light – produce less oxygen under green light
Bacteria move to where there is more oxygen
Unicellular responses to the environment 2
NaCl concentration (M) Number of contractions/min
0.00 6.5
0.01 6.2
0.02 6.0
0.03 5.7
0.04 5.5
0.05 4.9
0.10 4.4
0.15 3.9
0.20 1.2
effect of salt concentration on contractions
0
1
2
3
4
5
6
7
00.
020.
040.
060.
08 0.1
0.12
0.14
0.16
0.18 0.
2
Na Cl Concentration M
Nu
mb
er
of
co
ntr
ac
tio
ns
Number of contractions/min
Unicellular responses to the environment 2
NaCl concentration (M) Number of contractions/min
0.00 6.5
0.01 6.2
0.02 6.0
0.03 5.7
0.04 5.5
0.05 4.9
0.10 4.4
0.15 3.9
0.20 1.2
Contractile vacuole changes activity depending on salt concentration
Unicellular responses to the environment 3
• Euglena
Eyespot detects lightFlagellum moves organism toward slight or foodContractile vacuole changes activity depending on salt concentration
Surface area and volumeCalculate the volume and surface area for these:
Surface area and volumeCalculate the volume and surface area for these:
1 cubic unit 6 square units
8 cubic units
24 square units
Does size matter?
As size increases:What happens to volume?What happens to surface area?What happens to surface area to volume ratio?
Does size matter?
As size increases:What happens to volume?What happens to surface area?What happens to surface area to volume ratio?
decreases
increases
increases
Surface area and volume 2Size 1x1x1 2x2x2 3x3x3 4x4x4
Surface area
Volume
SA: Vol
Size of sides
10
2 3 4
Surface area
volume
SA:Vol
1
2
3
4
5
6
7
1
20
30
40
50
60
70
80
90
100
50
Surface area and volume 2Size 1x1x1 2x2x2 3x3x3 4x4x4
Surface area
6 24 54 96
Volume 1 8 27 64
SA: Vol 6:1 3:1 2:1 1.5:1
Size of sides
10
2 3 4
Surface area
volume
SA:Vol
1
2
3
4
5
6
7
1
20
30
40
50
60
70
80
90
100
50
Affect of shape on surface area and volume
Calculate the volume and surface area for these:2x 2x2
1x1x8
4x2x1
Affect of shape on surface area and volume
Calculate the volume and surface area for these:2x 2x2
1x1x8
4x2x1
8 cubic units
8 cubic units
8 cubic units
24 square units
28 square units
34 square units
Potato experiment
Starting the experiment:
Potato experiment 2
• What hypothesis is being tested?
• What was the control?
• What was the independent variable?
• What was the dependent variable
• What variables were controlled?
• Predict the results you will see.
Potato experiment 2
• What hypothesis is being tested?
• What was the control?
• What was the independent variable?
• What was the dependent variable
• What variables were controlled?
• Predict the results you will see.
Size or shape will affect the absorption of iodine
Smallest cube in water
Size & shapeof potato
Amount of mass gainedColour change
Results of potato experimentWhat can be seen?
What does this indicate?
Results of potato experimentWhat can be seen? – potatoes have turned black where
iodine has entered. What does this indicate? More iodine has entered the
smaller & flatter shaped ones. Larger shapes have less surface area for exchange & so iodine hasn’t reached their centres
Exchange of material
Occurs at the cell membrane
Involves the processes of diffusion, osmosis and active transport
Occurs slowly
How cells increase their surface area
• Size • Shape• Folding • Cell extensions
pseudopods
microvilli
Determining the components of the cell membrane
Beetroot lab – part A
acid base
water Distilled water
detergent
Beetroot experiment part A
• What hypothesis is being tested?
• What is the control?
• What is the independent variable?
• What is the dependent variable
• What variables are controlled?
• How will this tell you about the components of the cell membrane?
Size of objects under the microscope 1
Magnification x100, field of view 1500 m
Size of objects under the microscope 1
Magnification x100, field of view 1500 m
~ 500 m
Size of objects under the microscope 2
Magnification x400, field of view for x100 = 1600 m
Size of objects under the microscope 2
Magnification x400, field of view for x100 = 1600 m
Field of view for x400 = 400 m
Size = 400 m
Magnification and field of view -review 1
magnification x 40 magnification x 400
field of view 4000 m field of view m
Magnification has by a factor of
Field of view has by a factor of
Magnification and field of view - review 2
magnification x 100 magnification x 400
field of view m field of view 400 m
Magnification has by a factor of
Field of view has by a factor of
Label the cell
Label the cell
Cell membrane Mitochondrion
Golgi body
Vacuole
Smooth endoplasmicreticulum
Ribosomes
Rough endoplasmicreticulum
Cytoplasm
Nucleus
Nucleolus
Chromatin/DNA