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