BIOL1115: Lab 5 - Energy Transformations In Cells

what does life require?

energy

what is photosynthesis?

captures the energy of sunlight and converts it into a more easily usable form of complex organic compounds, carbohydrates (or sugars)

what organisms can perform photosynthesis?

- plants

- algae

- cyanobacteria

what is cellular respiration and fermentation?

metabolic pathways by which the energy from complex organic compounds can be released and converted into ATP

which organisms can perform both cellular respiration and fermentation?

- plants

- animals

- bacteria

- fungi

- protists

what is the equation for cellular respiration?

C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + ATP energy

what are the four stages of cellular respiration?

- glycolysis

- pyruvate processing (acetyl CoA Synthesis)

- citric acid cycle

- electron transport chain and oxidative phosphorylation

what is the role of oxygen in cellular respiration?

act as the terminal electron acceptor in the electron transport chain

what molecule captures approximately 34% of the energy released during cellular respiration?

ATP

what happens to the 66% of energy that is NOT captured as ATP during cellular respiration?

released as heat

do all the stages of cellular respiration occur in the mitochondrion?

no, glycolysis occurs in the cytoplasm

- pyruvate processing (mitochondrial matrix)

- citric acid cycle (mitochondrial matrix)

- ETC (inner mitochondrial membrane)

what happens to the carbon dioxide produced by cells in cellular respiration?

diffuses out of cells into the blood. it is transported (mainly as bicarbonate ions) to the lungs, where it diffuses from the blood into the alveoli and is then exhaled

what can carbon dioxide produced during cellular respiration react with?

water, to produce carbonic acid (H2CO3) and could decrease blood pH

what is the equation for blood pH/carbonic acid?

CO2 + H2O ⇌ H2CO3 ⇌ H+ + HCO3

what can changes in pH do?

have dramatic effects on the normal working of a cell. many proteins when subjected to a change in pH will denature

what is denaturation?

the loss of secondary and tertiary structure of the protein

what happens once the protein has loss its secondary and tertiary structure?

it no longer functions

how does the vertebrate body minimize change in blood pH?

through the bicarbonate buffer system

what does the body do to sequester the excess H+ produced when the CO2 dissolves in the blood?

there are excess HCO3- that are made by the kidneys and are presented in the blood that will react with the extra H+

what was the lab demonstration that demonstrated CO2 effects?

exhaling CO2 into flasks and observing pH changes in the presence and absence of a pH 9 buffer

what indicator was used in the CO2 demonstration and what colours were there?

bromothymol blue

- yellow (acidic, pH < 7)

- green (neutral, pH = 7)

- blue (basic, pH > 7)

what causes the bromothymol blue solution to turn yellow when you exhale into it?

the CO₂ in exhaled breath dissolves in water to form carbonic acid, lowering the pH below 7 (acidic), causing the solution to turn yellow

what is the reason flask B required more breaths than flask A to turn yellow?

flask B contained a pH 9 buffer which resists pH changes, so more CO₂ was needed to overcome it and make the solution acidic enough to turn yellow

why was it necessary to add an additional 10 mL of water to flask A in Step IV?

to act as a control, ensuring both flasks had the same total volume so that any difference in results was due to the buffer in flask B only, keeping the experiment a fair comparison

what can the consumption of oxygen be used as since it's used as a reactant in cellular respiration?

an indicator of cellular respiration activity

what is the finger pulse oximetre?

detect a person's oxygen saturation level and pulse

what is an oxygen saturation level?

the percent of hemoglobin in arterial red blood cells that is carrying oxygen

what is pulse rate?

the number of heart beats per minute

what is ventilation rate?

the number of inhale-exhale cycles per minute

what measurements increase after exercise compared to rest?

pulse rate and ventilation rate increase because muscles demand more oxygen and produce more CO₂, requiring the heart and lungs to work harder

what measurement stays the same after exercise and why?

O₂ saturation stays the same because the body compensates by increasing heart rate and breathing rate, keeping the blood fully oxygenated

what reasons explain variations in cellular respiration measurements between individuals?

differences in fitness level, age, body size, lung capacity, and overall health. fitter individuals show smaller increases because their bodies are more efficient at delivering oxygen

what does production of heat be an indication of?

that cellular respiration is occurring

what does the temperature increase in germinating seeds indicate?

that germinating seeds are actively undergoing cellular respiration, releasing energy in the form of heat as a byproduct of glucose breakdown

what does the lack of temperature change in dormant seeds tell us?

that dormant seeds are not actively respiring, so no heat is being produced

what process is responsible for heat production in germinating seeds and how do we know it is not photosynthesis?

cellular respiration, because the seeds are stored in a closed thermos flask with no light, making photosynthesis impossible as it requires light to occur

what happens in the absence of oxygen?

fermentation can occur to produce ATP

what is an example of fermentation in humans?

lactic acid fermentation

what happens during lactic acid fermentation?

occurs in muscle cells during intense exercise when oxygen supply runs out. glucose is broken down into lactic acid to continue producing ATP, causing a burning sensation in the muscles

what are yeasts?

single-celled fungi that can survive and even grow and reproduce using fermentation to supply their energy needs

what are yeasts known for?

their ability produce ethanol by alcoholic fermentation

what experiment demonstrated the production of CO2 during fermention?

the fermentation experiment using yeast, sucrose, and limewater

what is limewater (CaOH2)?

the classic test for the presence of CO2. CO2 reacts with the CaOH2 to form calcium carbonate (CaCO3) which precipitates out of solution according to the formula:

Ca(OH)2 + CO2 -> H2O + CaCO3

what does the presence of CaCO₃ in flask 1b tell us about yeast and sucrose?

it confirms that CO₂ was produced by the yeast and sucrose mixture, as CO₂ reacts with limewater (Ca(OH)₂) to form calcium carbonate (CaCO₃), turning it cloudy

what does the absence of CaCO₃ in flask 2b tell us about sucrose alone?

it confirms that sucrose alone cannot produce CO₂, yeast is necessary for fermentation to occur

what reagent is used to test for ethanol?

potassium dichromate and sulphuric acid

what is a positive control?

shows what positive results look like, also checks that reagents are working correctly

what is a negative control?

checks to be sure the compound that is being looked for isn't an accidental contaminant

what information can you obtain in the test tubes labelled "+C" in the alcohol fermentation experiment?

the colour change confirms that ethanol is present and that the reagents (potassium dichromate and sulphuric acid) are working correctly

what information can you obtain in the test tube labelled "-C" in the alcohol fermentation experiment?

no colour change confirms that no ethanol is present, showing that the reagents alone do not produce a colour change and that ethanol is not a contaminant

what information can you obtain in the test tube labelled "E" in the alcohol fermentation experiment?

the experimental tubes showed the same colour change as the positive control, confirming that yeast produced ethanol through fermentation under anaerobic conditions

what principle of good experimental design is shown by having duplications of each test tube in the alcohol fermentation experiment?

replication, because duplicates ensure results are reliable and not due to chance or error

what are the products of fermentation in yeast cells?

ethanol and CO2

are the same products of yeast fermentation found in human cells?

no, in human cells ethanol and CO2 does not get produced, instead lactic acid gets produced (lactic acid fermentation)

what is the major reactants and end products in fermentation in yeast?

Glucose -> 2Ethanol + 2CO2

what is the major reactants and end products in fermentation in humans?

Glucose -> 2Lactate

what is the summary equation of photosynthesis?

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

what does photosynthesis require?

energy, while respiration releases it

what is the waste products of cellular respiration?

raw materials for photosynthesis and the photosynthetic waste material, oxygen, is a critical reactant in cellular respiration

where does the plant get the energy to perform photosynthesis?

from sunlight, plants capture light energy using chlorophyll in their chloroplasts

what are the two stages of photosynthesis?

- light reactions (in the thylakoid membrane)

- calvin cycle (in the stroma)

what is glucose as a product in photosynthesis?

the high-energy molecule that can be used by all living cells for work or for building other organic molecules

what is the production of organic compounds by photosynthesis sometimes called

primary productivity

what is primary productivity?

the first and foremost production process upon which all other metabolic pathways depend

what are the primary producers?

plants, algae, and certain bacteria

what features allows the organisms to be primary producers and leaves the rest as dependent consumers?

chlorophyll

what happens to chlorophyll molecules in photosynthesis?

it becomes sufficiently energized by light waves to split water molecules. oxygen is a by-product and leaves the cell as a free gas.

what is the absorption spectrum?

shows which wavelengths of light a pigment absorbs

what two colours of light are absorbed best by chlorophyll?

red and blue-violet light

why do most plants appear green?

because chlorophyll reflects green light

what are accessory pigments that assist chlorophyll?

carotenoids (in plants) and phycobilins (in red algae)

what are carotenoids?

accessory pigments found in plant chloroplasts that absorb blue-green light and reflect yellow and orange wavelengths

what is a colour of a particular photosynthetic organism due to?

its particular mix of photosynthetic pigments plus any other pigments, such as anthocyanins, that may be there for such diverse reasons as pollinator attraction and UV protection

what are anthocyanins?

red, purple, or blue pigments that occur in all tissues of higher plants such as flowering plants. they do not contribute to photosynthetic activity

what is a common lab technique for separating mixtures?

chromatography

what is chromatography?

separates the pigments in a mixture on the basis of their different polarities

what do photopigments have?

one or more polar groups. the number of these groups will affect their tendency to "stick" to the chromatography paper and therefore affect the rate at which they migrate

what happens to pigments with fewer polar groups?

they are more soluble in the non-polar solvent, and less attracted to the polar paper, so they migrate further in the time allowed

what happens to pigments with more polar groups?

they stick to the paper and move a shorter distance

which pigment travels the furthest and why?

carotene, because it has 0 polar groups making it the least polar, it barely sticks to the paper

what is the cuticle of a plant?

helps plant resist drying

what is the epidermis of a plant?

protect the plant from water loss, disease-causing agents, and herbivores

what are the photosynthetic tissue of plants?

- palisade mesophyll

- spongy pesophyll

what is the palisade mesophyll?

primary site of photosynthesis in the leaf

what is the spongy mesophyll?

allows gases to diffuse through the leaf

what are the vascular tissues in plants?

xylem and phloem

what is the xylem?

conducts water and dissolved nutrients in one direction: from the root system to the shoot system

what is the phloem?

conducts sugar, amino acids, hormones, and other substances in two directions: from roots to shoots and from shoots to roots

what are guard cells in plants?

regulate gas exchange and water loss by opening and closing the stomata depending on conditions

what cells in the epidermis contain chloroplasts?

guard cells

what two cell layers does the majority of photosynthesis occur?

palisade mesophyll and spongy mesophyll

what pigment leaves the leaf during the first heating (in water)?

anthocyanin

what pigment is extracted from the leaf when alcohol is added?

chlorophyll

what have you learned about pigment solubility from the experiment?

anthocyanin is water-soluble and is removed when heated in water, while chlorophyll is not water-soluble but dissolves in alcohol and is only extracted when alcohol is used

what compound gives a positive reaction with iodine?

starch

what compound is stored in a photosynthesizing leaf?

starch

in which organelle is starch stored in?

chloroplasts (short-term daytime storage), but long-term in amyloplasts

why does only one leaf react with iodine?

only the leaf exposed to light carried out photosynthesis and produced starch, so it reacts with iodine. the dark-kept leaf did not photosynthesize, so no starch was produced