NUTRITION

* The activities by which organisms obtain and process materials needed for energy, growth, repair, and regulation.
* There are two types:

AUTOTROPHIC vs. HETEROTROPHIC
(makes food)........... (has to get food)

I. AUTOTROPHIC NUTRITION--
* the ability by which most plants and certain monerans (bacteria) and protists to manufacture organic compounds (has carbon and hydrogen) from inorganic compounds (does not have carbon and hydrogen)

A) Chemosynthesis: a way where monerans can get the nutrients they need directly from chemicals; these are not digested in any manner!

B) Photosynthesis: the process where plants, some protists, and some monerans can manufacture nutrients from light, water, and carbon dioxide

DURING PHOTOSYNTHESIS, LIGHT (RADIANT) ENERGY IS CONVERTED INTO THE CHEMICAL ENERGY OF ORGANIC MOLECULES!

Remember which organic compound supplies energy to living things....CARBOHYDRATES!

1) This chemical energy is where most of the energy used by living things comes from.

2) A waste product of photosynthesis is oxygen gas, which is let off by plants.

The sun is supplies the plants with a means to make their food, which is used for energy. This is then eaten by animals who then use this energy for themselves.


THE PROCESS OF PHOTOSYNTHESIS

* Most cells that carry out photosynthesis contain chloroplasts...

* ...which contain the green pigment chlorophyll, which absorbs the energy of the sunlight...which is actually all the colors of the spectrum together.

* The green light is reflected off the chlorophyll, which is why you see the plant to be green. Plants actually absorb the red and blue wavelengths of light the best!

Nutrition

a cute interactive demo showing the molecules of photosythesis
take a peek at how photosynthesis was discovered
watch as Dr. Rodriguez shows one reason why we study plants
take a look at some of the different pigments found in leaves

INSIDE THE CHLOROPLAST...

CO2 (carbon dioxide) + H2O (water)...are used to form simple sugar molecules and O2 (oxygen gas)

HERE IS THE "WORD" FORMULA...

carbon dioxide + water ------> glucose + water + oxygen

LIGHT
ENERGY
+
CHLOROPHYLL
+
ENZYMES

6CO2 + 12H2O ------> C6H12O6 + 6H2O + 6O2

...FOLLOWED BY MOLECULAR FORMULAS

PLANTS MAKE SIMPLE SUGARS...
a.k.a. GLUCOSE
a.k.a. MONOSACCHARIDES

So, what happens to the glucose after it is manufactured?

1) It is used as an energy source directly by the organism.
2) It can be synthesized into other metabolic compounds (lipids, proteins).
3) It can be converted to storage products, polysaccharides (starch!!!). This is done by the process of DEHYDRATION SYNTHESIS!
They can always be broken back down to monosaccharides by adding water, called HYDROLYSIS.


OKAY? NOW HERE'S THE TRICKY PART...

*There are 2 major reactions that happen in the choroplast during the process of PHOTOSYNTHESIS...

above is a chloroplast

These happen in the GRANA (stacks of layered membranes that contain enzymes and chlorophyll) and STROMA (a thick watery fluid that contains enzymes)

THESE REACTIONS ARE CALLED THE:

LIGHT REACTIONS (in the grana) and the DARK REACTIONS (in the stroma)

Nutrition

a cute interactive demo showing the molecules of photosythesis
what exactly makes most plants green?
do all plants get what they need from light, water, and oxygen...watch the answer to that question
A basic of review of photosynthesis
see how you can separate plant pigments in a neat home experiment

OKAY? NOW HERE'S THE TRICKY PART...

*There are 2 major reactions that happen in the choroplast during the process of PHOTOSYNTHESIS...

above is a chloroplast

These happen in the GRANA (stacks of layered membranes that contain enzymes and chlorophyll) and STROMA (a thick watery fluid that contains enzymes)

THESE REACTIONS ARE CALLED THE:

LIGHT REACTIONS (in the grana) and the DARK REACTIONS (in the stroma)

The Light (Photochemical) Reactions:
* here, light energy is changed into chemical energy

1) light hits the chlorophyll in the grana
2) the light energy does 2 things:

A) splits water (H2O) into hydrogen (H) and oxygen (O)--called PHOTOLYSIS--light/split (splitting with light); this is where we get the O2 (oxygen gas) to breathe!

B) creates ATP, which is used as energy

The Dark (Carbon Fixation) Reactions:
* here, carbon dioxide (CO2) molecules are changed to PGAL (phosphogylceraldehyde C3H6O3--which is 1/2 of a glucose molecule

* takes place in the stroma, enzymes combine CO2 and the hydrogen from the light reactions (from PHOTOLYSIS) into a molecule of the aforementioned PGAL...

* then, 2 PGALs combine to make one molecule of glucose (C6H12O6)

So, here's everything that happens:

1) Light from the sun hits the chlorophyll in the grana, where it then splits water (H2O) into hydrogen (H) and oxygen (O) by the process of the PHOTOLYSIS.

2) Carbon dioxide (CO2) and hydrogen (H)--from step #1combine to form PGAL (C3H6O3)in the stroma.

3) Then in the stroma, two PGAL (C3H6O3) molecules combine to form one molecule of glucose (C6H12O6).

 

Nutrition

a cute interactive demo showing the molecules of photosythesis
a nice overall review of photosynthesis

ADVANCED! here are two John Kyrk links of the light and dark reactions of photosynthesis

a brief look at the light reactions inside the chloroplast
more looks inside the chloroplast

ADAPTATIONS FOR PHOTOSYNTHESIS

* algae (either unicellular or multicellular) can absorb the necessary materials for autotrophic nutrition directly through its cell membrane.
* MOST photosynthetic reactions occur from algae in the world's oceans.
* in complex, terrestrial (land) plants, photosynthesis happens in leaves

LEAVES: are broad, flat structures that allow a lot of light (red and blue wavelengths are most effective--green is least effective) to be absorbed at once

Here is a cross section of a leaf...


* cuticle--the waxy coating that covers the top of a leaf; has 3 functions:

1) protects the inside of a leaf
2) prevents excess water loss
3) helps resist invasion by fungi-SKIN

* upper epidermis--the outer layer of cells; leaves have an upper epidermis and a lower epidermis

* palisade layer--the place in a leaf where most photosynthesis takes place;

P for photosynthesis P for palisade layer

* spongy layer--a layer of the leaf where gases (namely CO2 and O2) circulate; some photosynthesis happens here

S for sponge (full of air) S for spongy layer

* stomates--openings in the lower epidermis; allows the exchange of O2, CO2, and H2O between the internal (inside) and external (outside) environments; the size of the opening is controlled by the...

* guard cells--control the opening of the stomates; have a few chloroplast to use to obtain energy to open and close

* veins--larger tubes that carry materials; there are 2 types

1) XYLEM--carry water and materials up
2) PHLOEM--carry food down

Nutrition

plants under water?
review your leaf cross section parts with this interactive
II. HETEROTROPHIC NUTRITION--
* carried out by organisms that are UNABLE to make organic molecules form inorganic raw materials
* these organisms must obtain preformed organic molecules from their environment

PROCESSES FOR HETEROTROPHIC NUTRITION

1) ingestion--the process of taking in food

2) digestion--the process of breaking down larger food molecules to smaller soluble (easily dissolved) molecules; can happen inside the cell (intracellular) or outside the cell (extracellular--like us)

* there are 2 types of digestion...

A) mechanical digestion:

* foods are physically broken down so that it increases the surface area for enzymes to go to work
* this is accomplished by cutting, grinding, or tearing of food

B) Chemical Digestion:

* where large, insoluble (hard to dissolve) molecules are changed chemically by enzymes to smaller, more soluble molecules by the process called ENZYMATIC HYDROLYSIS (using enzymes) (to split with water)

 

LARGE MOLECULES END PRODUCT

carbohydrates ----------------> simple sugars

lipids ----------------> fatty acids & glycerol

proteins ----------------> amino acids


3) egestion--the removal of undigested or indigestible material; heterotrophs might not be able to digest all foods because they may not have all the needed enzymes.

 

Nutrition

ADAPTATIONS FOR HETEROTROPHIC NUTRITION

Here are a few examples of how different heterotrophs from different kingdoms carry out the process of getting their food.

I. FUNGI--

* multicellular fungi live in or directly on their food supply
* fungi use filaments (tubes) called rhizoids which secrete enzymes right on the food; the food is digested OUTSIDE the fungus (this is an example of EXTRACELLULAR DIGESTION)
* the nutrients are then 'funneled' up the rhizoids (like a straw)

II. PROTOZOANS--

* these are the animal-like protists
* protists do not have organs because they are unicellular (have one cell)
* food is digested INSIDE the cell (INTRACELLULAR DIGESTION) with the help of lysosomes

A) AMEBA
* food is ingested by pseudopods ("fake feet") that surround and engulf food particles by the process of PHAGOCYTOSIS
* once food is absorbed, it is stored in a FOOD VACUOLE, where lysosomes combine with it.
* any waste products are stored in a VACUOLE until shipped out of the cell


B) PARAMECIUM--
* the sweeping action of small hairs (CILIA) on the outside of the paramecium move food to the ORAL GROOVE
* the food particles are then enclosed in a FOOD VACUOLE inside the cell
* INTRACELLULAR DIGESTION occurs as a lysosomes come over to it and digests it
* the end products of digestion that are not utilized by the cell are released through a fixed opening called the ANAL PORE

*paramecium also have a CONTRACTILE VACUOLE to help keep the water level in the cell balanced

Nutrition