BIOL& 160: Exam 2

define photosynthesis

process by which solar energy is stored as chemical energy in the bonds of sugar

what kind of organisms carry out photosynthesis

photoautotrophs

ex: plants

why do all organisms rely on photosynthesis

organisms either directly create energy/food or become that source for others

what is the chemical formula for photosynthesis

6CO2 + 6H2O + light energy —> C6H12O6 + 6O2

what part of the electromagnetic spectrum reaches the earth and how does it emits energy

visible light, which emits energy via long or short wavelengths

which wavelengths of light have more energy

short, tight waves

how do plants and other photosynthesizers absorb the energy from sunlight

chlorophyll in chloroplasts give up an excited electron which is brought to the ETC and stored as ATP and NADH

what is the role of pigments in absorbing energy in sunlight

pigments absorb many different wavelengths of light and the wavelengths = energy

mesophyll cells

middle layer of leaves containing chloroplasts

thylakoids

stacked, disc shaped structures in chloroplasts where light-dependent reactions occur

granum

stack of thylakoids

stroma

space/fluid surrounding granum where calvin cycle occurs

stomata

small, regulated openings where exchange of carbon dioxide and oxygen occurs

explain how photosystems work in light reactions

photosystems are made up of pigment molecules which absorb light energy (photons)

what is the light/light-dependent reaction of photosynthesis and what are the reactants and products

chlorophyll and other molecules embedded in chloroplast thylakoid membranes capture sunlight energy and convert some into chemical energy

• reactants: H2O, sunlight energy, NADP+, and ADP

• products: O2, ATP, and NADPH

what is the carbon/calvin cycle reaction of photosynthesis and what are the reactants and products

enzymes in stroma use CO2 and chemical energy from energy carriers to synthesize a 3 carbon sugar that will be used to make glucose

• reactants: CO2, ATP, and NADPH

• products: C6H12O6, ADP, and NADP+

know the specific steps of the light reactions starting with pigments absorbing energy from the sunlight and electrons moving down the ETC. include the process of how chemiosmotic phosphorylation produces ATP

• pigment molecule in photosystem absorbs one photon

• photon travels to chlorophyll and excited electron breaks free from chlorophyll

• water molecule is split to replace electron

• results in O2 and H+ in thylakoid space

• energized electron travels along ETC II and H+ is pumped into thylakoid space

• pumping creates a high concentration of H+ inside the space to the surrounding stroma

  • H+ flows down its concentration gradient through a thylakoid channel protein (ATP synthase), generating ATP from ADP

know the steps of the carbon reactions and how sugar is produced in these reactions. explain the interactions between ribulose bisphosphate (RuBP), RuBisCO, and CO2 in the reactions

• CO2 enters through the stomata and diffuses into the stroma

• RuBisCO catalyzes a reaction between CO2 and RuBP which forms a 6 carbon compound that is converted to two 3 carbon compounds

• ATP and NADPH use stored energy to convert the 3 carbon compound (3 PGA) to G3P

• ADP and NADP+ go back to light reactions and G3P leaves calvin cycle to form glucose (6 carbon atoms = 6 cycles)

  • remaining G3P molecules regenerate RuBP to prepare for start of carbon reaction

explain the different between C3, C4, and CAM plants

• C3: use a 3 carbon compound called 3 PGA, carbon fixation and calvin cycle both occur in mesophyll cells, and stomata are open during the day (suited for cool and temperate environments)

• C4: use a 4 carbon compound called malate, CO2 is captured in mesophyll cells but calvin cycle occurs in bundle sheath cells, and stomata are open during the day (suited for warm and tropical environments)

• CAM: use a 4 carbon organic acid called malic acid, open stomata at night to take in CO2 to fix acid using PEP, but close stomata during the day and run calvin cycle (suited for hot and desert environments)

what is aerobic cellular respiration

the process by which cells break down glucose into usable energy

explain the role of ATP, carbon dioxide, and oxygen in cellular respiration

• ATP is the energy that cells are trying to capture

• carbon dioxide is a waste product

• oxygen is an electron acceptor at the end of the ETC and ensures ATP generation continues

what is the chemical formula for cellular respiration

C6H12O6 + 6O2 —> 6CO2 + 6H2O + ATP energy + heat energy

why does cellular respiration occur in a series of small steps instead of all in one step

too much energy would be released all at once and cells wouldn’t be able to trap it safely

what are the specific steps in cellular respiration

glycolysis, acetyl CoA formation, krebs cycle, and oxidative phosphorylation (ETC and chemiosmosis)

what is happening during glycolysis and what are the inputs and outputs

glucose splits into 2 pyruvate molecules and energy/electrons are harvested to produce some ATP

• inputs: 1 glucose molecule, 2 ATP, and 2 NAD+

• outputs: 2 pyruvate molecules, 4 ATP (net gain = 2), and 2 NADH

what is happening during acetyl CoA formation and what are the inputs and outputs

pyruvate is transformed into a 2 carbon acetyl group which is picked up by coenzyme a

• inputs: 2 pyruvate, 2 CoA, and 2 NAD+

• outputs: 2 acetyl CoA, 2 CO2, and 2 NAD

what is happening during the krebs cycle and what are the inputs and outputs

acetyl CoA attaches to a 4 carbon molecule, creating a 6 carbon molecule (citric acid) which is stripped so the electrons can be brought to the ETC to generate more energy

• inputs: 2 acetyl CoA, 6 NAD+, and 2 FAD

• outputs: 4 CO2, 6 NADH, 2 FADH2, and 2 ATP

what is happening during the electron transport chain and what are the inputs and outputs

electrons are passed from one complex to the next until they reach oxygen —> oxygen combines with hydrogen ions in intermembrane space to form water —> hydrogen ions form an electrochemical gradient and pass through the inner membrane via ATP synthase which produces ATP

• inputs: 10 NADH, 2 FADH2, and 6 O2

• outputs: 10 NAD+. 2 FAD, 6 H2O, and 32 ATP

where does aerobic cellular respiration occur in prokaryotes

glycolysis and krebs cycle = cytoplasm

etc = plasma membrane

where does aerobic cellular respiration occur in eukaryotes

glycolysis = cytoplasm

krebs cycle = mitochondrial matrix

etc = inner mitochondrial membrane

what is happening at each step of glycolysis

• energy investment stage: phosphate groups and energy from each of the 2 ATP are added to glucose to produce fructose bisphosphate —> broken down into 2 G3P molecules

• energy harvesting stage: the 2 G3P molecules are converted into 2 pyruvate molecules, resulting in 4 ATP and 2 NADH molecules (NAD+ is reduced)

what happens to the pyruvate molecule from glycolysis in preparation for the krebs cycle? explain how this is an oxidation reduction reaction

pyruvate is split, forming a 2 carbon acetyl group and releasing CO2 —> acetyl group reacts with coenzyme a, forming acetyl CoA

• during the reaction, NAD+ picks up electrons removed from the acetyl group and a hydrogen ion, reducing to NADH

what molecule does acetyl CoA react with at the beginning of the krebs cycle

a 4 carbon molecule called oxaloacetate

what is happening at each step of the krebs cycle

acetyl CoA and oxaloacetate reaction releases CoA and forms a 6 carbon citrate molecule —> citrate is oxidized and high energy electrons and H+ are picked up by NAD+ and FAD —> NADH and FADH2 are formed

• each acetyl group produces 3 NADH, 1 FADH2, and 1 ATP

what is the role of NADH and FADH2 in the ETC

they are electron carriers

why is oxygen needed in the ETC

it accepts spent electrons and combines them with H+ from the mitochondrial matrix forming H2O

• this ensures the ETC doesn’t get backed up and stop

describe the pathway of electrons down the ETC

electrons are passed through protein complexes 1 - 4 —> released energy pumps H+ from matrix to intermembrane space creating electrochemical gradient —> H+ can only flow back to the matrix through ATP synthase —> this produces ATP

where is ATP produced in all the steps of aerobic cellular respiration and how many molecules are produced in each step and in total

glycolysis = cytoplasm, 2 ATP

krebs cycle = mitochondrial matrix, 2 ATP

etc = inner mitochondrial membrane, 32 ATP

• total = 36 ATP

explain how other molecules such as carbohydrates and proteins enter the cellular respiration pathway to extract energy

• glycogen can be taken out of storage if extra energy is needed and will enter glygolysis

• amino acids can enter at different stages depending on what the body needs, but amino group has to be removed first

why is NAD+ required in glycolysis

it is an electron acceptor

• when electrons and H+ are removed from G3P, it accepts them and allows glycolysis to continue

how is NAD+ regenerated in aerobic respiration

it’s regenerated by the ETC

• NADH drops off electrons and H+, changing it back to NAD+

how is NAD+ regenerated in anaerobic respiration

it’s regenerated by the ETC except there’s a different organic molecule accepting electrons at the end ensuring the ETC doesn’t back up

how is NAD+ regenerated in lactic acid fermentation

lactate dehydrogenase transfers electrons and H+ from NADH to pyruvate creating lactic acid and NAD+

how is NAD+ regenerated in ethanol fermentation

pyruvate loses CO2 to make acetaldehyde and NADH loses electron to form NAD+ —> acetaldehyde accepts electron becoming ethanol

how are photosynthesis and cellular respiration related

they are inverse processes

compare which molecules are consumed and released in photosynthesis and cellular respiration

photosynthesis

• consumed: CO2, H2O, and light energy

• released: C6H12O6 and O2

cellular respiration

• consumed: C6H12O6 and O2

• released: CO2, H2O, ATP, and heat energy

describe the sexual life cycle of eukaryotic cells and where mitosis and meiosis fit into this cycle

divide, grow, differentiate, and divide again

• mitosis: allows for asexual reproduction of cells

• meiosis: allows for sexual reproduction

what role does mitotic cell division have in the life of organisms

allows for cell growth, tissue repair and regeneration, and asexual reproduction

what role does apoptosis have in the life of organisms

it eliminates damaged cells or ones that could cause harm to the body (programmed cell death)

what is DNA replication and why does it needed to occur

process of making an identical copy of a cell’s DNA, which is important so daughter cells receive complete and accurate genetic information

how is DNA replication a semiconservative process

each double strand is made up of one parental (old) strand and one complementary (new) strand

what are the molecular mechanisms involved in producing the leading strands at the replication fork

primase adds a single RNA primer and DNA polymerase continuously adds nucleotides

what are the molecular mechanisms involved in producing the lagging strands at the replication fork

primase repeatedly synthesizes RNA primers since this strand is built in fragments (okazaki) and DNA ligase joins the fragments into a strand at the end

how do prokaryotes divide their DNA

binary fission

describe the steps involved in binary fission

prokaryotic chromosome (circular DNA double helix) is attached to the plasma membrane at a point —> DNA replicates and resulting 2 chromosomes attach to plasma membrane at nearby points —> new plasma membrane is added between the attachment points, pushing the 2 chromosomes farther apart —> plasma membrane grows inward at middle of cell, creating 2 identical cells

what does it mean when chromosomes condense before eukaryotic DNA replication

they go from being long and string-like to tightly coiled making transport easier and ensuring no tangling or breakage

chromatin

long, string-like form of the DNA protein complex

chromosome

tightly coiled chromatin

chromatid

one half of a replicated chromosome

what are the phases involved in the cell cycle

interphase, mitosis, and cytokinesis

name the 3 parts of interphase and what happens in each of these phases

• G1: time for acquisition of nutrients and growth to proper size

• S: characterized by DNA synthesis during which every chromosome is replicated

• G2: includes completion of cell growth and preparation for division of the cell

how is interphase different from mitosis

interphase is cell growth and DNA replication

mitosis is when the DNA and cell contents separate and cell divides in 2

what are the phases of mitosis

prophase, metaphase, anaphase, and telophase

prophase/prometaphase

• chromosomes condense and become visible