Photosynthesis and Cellular respiration

How are plants and humans similar?04-03-2013

Topic of this Unit

• Topic: photosynthesis and cellular respiration

Topic of today

• Topic: Energy

• Learning goals:– After todays lesson you will be able to:• Describe what is energy?• List the different types of energy• Explain in what ways energy can be converted

Energy

• What is energy?– It has the capacity to cause change

• Energy in everyday life– Examples...?

Energy

• Energy in everyday life (examples)– you expend energy to turn the pages of this book– your cells expend energy in transporting certain

substances across membranes

• Energy exists in various forms, and the work of life depends on the ability of cells to transform energy from one form to another.

Forms of energy

• Free energy • Bound energy

• Free energy forms:– Warmth– Movement (Kinetic energy)– Light– Electricity– Sound

• Bound or fixed energy (potential energy) can be seen as stored energy.

HydroelectricityGlen Canyon Dam

Hydroelectricity• Around the dam the water is highly elevated, there is a lot of

potential energy• Water falls down from high altitude potential energy is

released or becomes free as kinetic energy (movement)• The falling water brings a turbine in motion, which generates

electricity• Motion energy is transformed in

electric energy

Battery

• This electric energy can be used to charge a battery

• So this kinetic electric energy can be transformed again in fixed/bound energy in a battery

• The energy stored in the battery can later be released as either light, motion, warmth, sound, etc.

How is energy converted from one form to another?

1

2

3

4

1. What energy is converted into another type of energy here?2. What type of energy has become more now that he is elevated above

the water?3. What energy is converted into another type of energy here?4. What type of energy has become less now that he is in the water instead

of on the platform?

Assignment: Fill in the gaps

• Use the following words: chemical, kinetic (2x), potential (2x)

• The young woman climbing the ladder to the diving platform is releasing _______ energy from the food she ate for lunch and using some of that energy to perform the work of climbing. The _______ energy of muscle movement is thus being transformed into _______ energy due to her increasing height above the water. The young man diving is converting his _______ energy to _______ energy, which is then transferred to the water as he enters it. (A small amount of energy is lost as heat due to friction.)

Answer

• The young woman climbing the ladder to the diving platform is releasing chemical energy from the food she ate for lunch and using some of that energy to perform the work of climbing. The kinetic energy of muscle movement is thus being transformed into potential energy due to her increasing height above the water. The young man diving is converting his potential energy to kinetic energy, which is then transferred to the water as he enters it. A small amount of energy is lost as heat due to friction.

Chemical energy• Free energy can also be converted into chemical energy

• Complex molecules, such as glucose, are high in chemical energy.

• Catabolic reaction– some bonds are broken and others formed, releasing energy and

resulting in lower-energy breakdown products.

Example car engine:• This transformation also occurs, in the engine of a car when the

hydrocarbons of gasoline react explosively with oxygen, releasing the energy that pushes the pistons and producing exhaust.

Chemical Energy Lunch at WIS

• Similar reaction in biological systems • Food molecules with oxygen provides chemical energy• Producing carbon dioxide and water as waste products

• Biochemical pathways enable cells to release chemical energy from food molecules and use the energy to power life processes.

Assignment

During summer apples grow bigger and bigger. Around the beginning of autumn the apple falls from the tree. When you find this apple in the grass, you can of course eat this nice and tasty apple.

Think-pair-share: 1. Describe, first on your own, the forms of energy found in

an apple as it grows on a tree, then falls, then is digested by someone who eats it.

2. Discuss and compair your answer with your neighbour.3. Share your answer with the rest of the class.

Answer

• The apple has potential energy in its position hanging on the tree, and the sugars and other nutrients it contains have chemical energy.

• The apple has kinetic energy as it falls from the tree to the ground.

• Finally, when you eat the apple and it is digested and its molecules broken down, some of the chemical energy is used to do work, and the rest is lost as thermal energy.

Assimilation and Dissimilation

• In cells molecules are constantly converted into other molecules.The total of these chemical processes = Metabolism

• Part of these metabolism reactions consists of building bigger molecules from smaller molecules

• In bigger molecules atoms are held together by energy-rich bonds

• Free energy is needed to create these bonds• During the breakdown of an organic molecule this energy from

this bond is again released

Assimilation

• The construction of bigger molecules out of smaller molecules

• Organic compounds are formed by the process of assimilation, which give rise to our cells– Photosynthesis

Dissimilation

• The breakdown of organic compounds into smaller molecules

• Energy released by the process of dissimilation is used for processes in the cell– Combustion (= dissimilation with oxygen)

Autotrophic vs. Heterotrophic

• Autotrophic:– Able to construct organic compounds from

inorganic compounds, like CO2 and H2O carbon assimilation

Needed:– Free energy (plants use sunlight)

Autotrophic vs. Heterotrophic

• Heterotrophic:– NOT able to construct organic compounds from inorganic

compoundsNeeded:– Fixed or bound energy

• Great portion of organic compounds taken in by eating food are broken down into smaller organic molecules (digestion)

• These organic molecules can be dissimilated into even smaller compounds or used to build other organic compounds

The cell’s energysource

• Three main kinds of cell’s work:1. Chemical work • the pushing of reactions that would not occur

spontaneously, such as the synthesis of polymers from monomers

2. Transport work • the pumping of substances across membranes against the

direction of spontaneous movement

3. Mechanical work• the beating of cilia, the contraction of muscle cells, and the

movement of chromosomes during cellular reproduction

ATP

• Adenosine triphosphate (ATP)– Molecule to transfer chemical energy from one

compound to another

ADP

• When third phosphate group is split off by hydrolysis ADP (adenosine diphosphate) + energy is formed

ATP cycle• During dissimilation energy is released• This energy can be used to bind a phosphate

group to ADP again making ATP phosphorylation

Recapping

• What have we learned so far?

Plant and Animal Cells

• What are the differences between plant and animal cells?

Assignment Animal and Plant Cells

Wroclaw University of Science Cell Art Competition

Plant cells and Animal CellsCell structure/organelle Function Present in

Animal cell?Present in Plant cell?

Plasma membrane

Nucleus

Golgi apparatus

Chloroplast

Cell wall

Mitochondrion

Cytoplasm

Ribosome

Vacuole

Endoplasmic reticulum (ER)(Rough ER and Smooth ER)Plasmodesmata

In plant cells but not in animal cells: -

---