Chapter 4 Cellular Process - Weebly



Chapter 4 Cellular Process

I. Cellular Energy

A. Autotrophes – organisms that make their own food. (plants and algae)

B. Heterotrophes – organisms that depend on other organisms for their energy. (animals, fungi, and most bacteria).

C. Photosynthesis- converting absorbed light energy into stored chemical energy. * One of the most important biological processes. * Green plants use water, affect the air, require light and make organic matter.

1. Chlorophyll and light- chlorophyll is the green colored pigment which is the primary catalyst (speeds up but not changed) of photosynthesis.

a. iron is necessary for chlorophyll to be formed in plants. (when plants lack iron they look pale and yellow- lack chlorophyll).

b. Chlorophyll – found in the grana of chloroplast. (where they replace some of the lipids in the grana membrane).

2. ATP – adenosine triphosphate – small unit of energy stored in this molecule.

a. Made up of : 1 adenosine and 3 phosphate groups.

b. Between each phosphate group are high energy bonds.

c. ATP is found in the mitochondria.

d. When an ATP is used for energy, one phosphate is broken and energy is released. The bond molecule is then called ADP – adenosine diphosphate.

e. Your body can recycle the ADP and one phosphate group and form ATP.

3. Conditions for photosynthesis

a. proper temperature – best at 70 F.

b. proper amounts of water. * Hot dry summer days – many plants cease photosynthesis.

4. Process of Photosynthesis

a. chlorophyll absorbs light energy

b. photolysis occurs – energy from chlorophyll is used to break apart a water molecule.

c. Oxygen is released - from the water molecule. Some are used in the cytoplasm, some escape into the environment as 02 (oxygen gas).

d. Hydrogen and electrons are bonded. – they are passed from one carrier molecule to another.

e. An ATP molecule is made – from the energy of the energized chlorophyll.

f. Carbon dioxide is fixed. CO2 bonds with RuDP- this is unstable and splits into two PGA molecules (3carbon sugar w/P)

g. PGA is converted to PGAL – using product of the photophase

h. H2O is given off – into the stroma- during the conversion of PGA to PGAL

i. PGAL is converted to glucose.

5. Photosynthesis occurs in two separate steps.

a. photophase – light reactions – light energy is absorbed and energizes a chlorophyll-a molecule.

1. H2O broken apart * photolysis – breaking apart of water by energized chlorophyll

2. Form ATP from ADPs plus phosphates

• when water is broken apart, oxygen is released in the cell and the concentration becomes high. Some escapes into the atmosphere. The H and some electrons pass from one carrier molecule to another ( energy is released one ATP is made.

b. dark phase – dark reactions – can take place in the presence of light or in the dark but requires the products of light reaction . CO2 is used and split and glucose is formed.

D. Cellular Respiration

1. Break down of a food substance into usable cellular energy in the form of ATP

a. aerobic – requiring oxygen

b. anaerobic – not requiring oxygen

2. Aerobic Respiration (see equation on board)

(Glucose) C6H12O6 + O2 ( H2O + ATP + CO2

3. Comparing photosynthesis/respiration

Photosynthesis Respiration

- captures light energy - uses stored chemical energy

- converts to stored

chemical energy

- converts to, ready to use chemical energy (ATP)

- occurs in chloroplast - occurs in mitochondria

- occurs in autotrophes - occurs in all organisms that require oxygen to live

4. ATP energy from a glucose molecule (3-step process)

a. glycolysis – 2 ATP molecules are gained

b. citric acid cycle – 2 ATP molecules are gained

c. hydrogen – electron transport system – 32 ATP molecules gained.

5. 3 phases of cellular respiration

a. glycolysis – first phase – break down of glucose into pyruvic acid. (takes place in the cytoplasm.) The products (pyruvic acid, hydrogen and electrons) are shuttled to the mitochondria. (requires 2 ATP –makes 4ATPs – net gain is two ATPs).

b. citric acid cycle – (krebs cycle) second phase of cellular respiration (takes place in the mitochondria). – gives off H, CO2 and electrons (net gain of 2ATPs)

c. Hydrogen electron transport system – third step in cellular respiration. – enzymes and carrier molecules are bound to the membranes of the cristae in the mitochondria. As electrons pass from one enzyme to the next, energy is lost. The energy is enough to form ATP. At the end of the chain, O binds with two hydrogens to form water. (32 ATPs are gained.) Therefore, O must be present or the chain shuts down and ATP is not made. Cell will start to shut down.

6. Cellular Fermentation – breakdown of food w/o oxygen.

a. alcoholic fermentation - an alcohol molecule is formed from pyruvic acid and carbon dioxide is given off. Ex: bacteria carry on this process in the formation of alcoholic beverages and by yeast in baking. In baking the alcohol is evaporated and the carbon dioxide causes the bread to rise.

b. Lactic acid fermentation – pyruvic acid is converted to lactic acid. Produces only two ATPs. EX: bacteria form yogurt and cottage cheese by this process.

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