Exam 2 Flashcards
Metabolism
Sum of all chemical reactions in an organism.
Thermodynamics (first two laws)
- Energy can’t be created or destroyed. - It is transferred between forms.
- Energy transfer always increases entropy - Never perfect transfer of energy.
Spontaneous reactions release _____ energy.
Free.
Free energy - The energy of a system that can be used to do work.
Nonspontaneous vs spontaneous reactions
Reactions that do not release free energy. - nonspontaneous
A spontaneous process occurs without the need for a continual input of energy from some external source, while a nonspontaneous process requires such.
Endergonic - nonspontaneous
Exergonic - spontaneous
Endergonic Reactions
Require an input of free energy. Nonspontaneous. Creates more products than reactants. Ex: photosynthesis. (positive change of Gibbs free energy).
If a reaction is endergonic, ATP can be used by an enzyme to power the reaction.
Exergonic Reactions (provide example as well)
Release free energy. Spontaneous. More reactants than products. Ex: ATP hydrolysis. (negative change of Gibbs free energy)
ATP/ADP
ATP is the most commonly used cellular “energy molecule”. ATP has much more free energy than ADP and P. ATP can be hydrolyzed. ADP and P can undergo dehydration synthesis to make more ATP.
What does ATP do?
ATP powers reactions in a cell that increase order and/or are endergonic (non-spontaneous).
ATP phosphorylates transport proteins.
ATP binds noncovalently to motor proteins and then is hydrolyzed.
ATP hydrolysis.
ATP hydrolysis is a chemical reaction that breaks a phosphate bond on ATP, a molecule that stores and supplies energy in cells.
What makes an enzyme function different than other enzymes?
Their shape and molecular properties.
Enzymes hold onto substrates using weak forces. The interaction can change the shape of the enzyme.
Ways that stabilize the transition state of enzymes:
Bending the substrate(s)
“Micro conditions” of a reaction
Aligning two substrates next to each other in the correct orientation.
Activation Energy
All reactions require some energy to go.
Enzymes reduce the activation energy of a reaction by bending substrates, positioning them next to each other.
Denaturation
Enzymes are held together by weak bonds that can be broken easily by heat or other changes to the environment. Temperature, PH, osmolality, and other conditions can denature enzymes.
How is aerobic respiration powered?
Eating and breathing.
Oxygen is a reactant in breaking down food, CO2 is a waste product and is exhaled.
Is food being broken down exergonic or endergonic?
Is energy to convert adp and p to atp exergonic or endergonic?
exergonic
endergonic
Photosynthesis vs cellular respiration
opposite chemical reactions that transform energy from one form to the other
Photosynthesis
Uses H2O and CO2 with light energy to build glucose.
6CO2 becomes reduced and 6H2O becomes oxidized.
Fixes carbon which can be used to build organic molecules.
Plants, protists (algae), bacteria.
Cellular Respiration
Cellular respiration uses O2 and glucose to generate ATP and leaves CO2 and H2O.
Oxidizes glucose and reduces oxygen
Oxidizing Reactions
Reactions that remove hydrogen (and electrons)
Reducing Reactions
Reactions that add hydrogen (and electrons)
Redox Reactions
reducing/oxidizing reactions. These reactions are complementary, one gets reduced the other gets oxidized.
NAD+
Glucose becomes oxidized while NAD+ becomes reduced in several steps of cellular respiration.
What is cellular respiration?
A metabolic process that builds ATP from ADP and P.
Cellular Respiration breakdown into 3 stages
Glycolysis
Citric acid cycle
Oxidative phosphorylation
Glycolysis
Splits glucose into pyruvate and generates a small amount of ATP.
Splits sugar into 2 pyruvate molecules and generates 2 ATP and 2 NADH.
Citric Acid Cycle
Completes the breakdown of glucose and generates a small amount of ATP (and a lot of NADH).
Oxidative Phosphorylation
Uses NADH and O2 to phosphorylate ADP into ATP.
Phosphorylate - Introduce a phosphate group into a molecule or compound.
Glycolysis Steps
1.) Uses 2 ATP to phosphorylate glucose.
2.) The double phosphorylated 6 carbon intermediate is split
3.) Oxidizes the phosphorylated 3 carbon molecule to produce NADH
4.) Generates 4 ATP molecules.
Pyruvate Oxidation
Moves pyruvate into the mitochondria and converts it into acetyl CoA.
Citric Acid Cycle Steps
1.) Acetyl is added to Oxaloacetate making a 6 carbon sugar.
2.) Two carbons are released as CO2, and 2 NADH are produced. (Carbon is released, NADH is produced)
3.) Redox reactions regenerate oxaloacetate.
Where is most of the ATP made during cellular respiration generated?
Oxidative phosphorylation
Oxidative Phosphorylation Steps
1.) The electrons from NADH and FADH2 are used to pump H+ into the intermembrane space. (Move down electron transport chain)
2.) H+ diffuse through the ATP synthase enzyme, which uses their kinetic energy to build ATP.
What is needed to start photosynthesis and what are the biproducts?
CO2 H2O and Sunlight
O2 and Glucose
What is needed to start Cellular Respiration and what are the biproducts ?
Glucose and O2
Generates ATP, leaves CO2 and H2O
What would happen to cellular respiration if you stopped breathing?
All 3 parts of respiration could potentially stop
(potentialy beacuse alternative metabolic pathways can oxidize NADH into NAD+ allowing glycolysis to continue even in the absence of oxygen. ex. anaerobic respiration - lactic acid fermentation and ethanol fermentation)
- electrons cant be transferred to NADH to make NAD+ which would stop glycolysis and citric acid cycle.
Ethanol Fermentation
Yeast can recycle NAD+ through ethanol fermentation.
Lactic Acid Fermentation
Animals can perform this, which allows glycolysis to continue in the absence of oxygen when NAD+ is needed.
-a metabolic process by which glucose or other six-carbon sugars (also, disaccharides of six-carbon sugars, e.g. sucrose or lactose) are converted into cellular energy and the metabolite lactate, which is lactic acid in solution.
What does Dinitrophenol (DNP) do?
It makes the mitochondrial membrane leak H+.
What does Oligomycin do?
It blocks the ATPsynthase enzyme which stops ATP production.
Calvin Cycle
Enzymes in the chloroplast stroma use ATP and NADPH to fix carbon.
-Builds CO2 into sugars
- NADPH generated in light reactions is used to add hydrogen to CO2.
- ATP generated in the light reactions is used to drive the Calvin cycle reactions.
Where does photosynthesis occur?
In the chloroplast and uses the architecture of the thylakoid membrane.
Where are chloroplast found?
mesophyll cells
Thylakoid membrane
Chloroplast’s phospholipid membrane - creates cavities in chloroplasts.
Holds chlorophyll pigments that absorb light.
Why is photosynthesis so scattered across life?
Endosymbiosis - Eukaryotic cells engulfed photosynthetic prokaryotes, forming a symbiotic relationship.
Likely came through an endosymbiotic relationship with cyanobacteria.
Over time, the bacteria lost their autonomy and became organelles rather than individuals inside cells.
What changed the atmosphere from a reducing to an oxidizing atmosphere?
Photosynthesis, through releasing oxygen.
How do we know that oxygen is released from water during photosynthesis?
Many experiments, Isotope experiment - Oxygen 18 was used in CO2 and given to a plant with the output expected to be Oxygen 18 in photosynthesis, when this wasn’t the case, we realized Oxygen was released from H2O during photosynthesis.
Photosynthesis equation and how it works:
6CO2 + 12H2O + light = C6H12O6 + 6H2O + 6O2
All of the Oxygen in the products comes from the H2O in the reactants.
Light Reactions
Use light energy to generate ATP and add Hydrogen from water to NADP+.
Light reactions produce ATP, NADPH, and O2.
Summary:
- Photon strikes chlorophyll and excites an electron
- Electron is used to generate ATP
- Electron is re-excited and given to NADP+.
How is ATP generated in chlorophyll (light reactions)?
Excited electron is passed to an electron transport chain and used to generate ATP.
How is NADPH created in light reactions (in chlorophyll)?
The electron is passed to the next photosystem (PS1) where it is re-excited by a second photon of light and given to NADP+ in the outside of the thylakoid.
- Generation of NADPH reduces the concentration of H+ is the stoma.
What does the light reactions do for the calvin cycle?
Release O2, generate ATP and NADPH for the calvin cycle.
Where does the Calvin cycle occur?
It occurs in the chloroplast stroma outside the thylakoid.
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Steps of Calvin Cycle
1.) Add 3 molecules of CO2 to 3, five carbon molecules, and split into 6 three-carbon molecules. (fixes atmospheric carbon into organic carbon via enzyme rubisco)
2.) Add hydrogen (reduce) to each (6) of the 3 carbon molecules, and remove one. (reduce and remove G3P)
3.) Rebuild the starting molecules.
What are the three kinds of cell division?
Binary fisssion, Mitosis, and Meiosis.
Binary Fission
How prokaryotes reproduce.
Asexual reproduction.
The cell lengthens then splits.
Mitosis
Asexual reproduction
Unique to eukaryotes and is “general” cell division.
Daughter cells are genetically identical.
Meiosis
Sexual Reproduction
Unique to gametes (sex cells) of eukaryotes.
Reduces the amount of chromosomes by half.
How do bacteria and archaea reproduce and grow their populations?
binary fission - creates clones, genetically very similar, mutations are why they aren’t exactly similar.
How many copies of each chromosome do eukaryotes have in a normal cell?
2 copies of each chromosome (diploid, 2n)
Humans have 23 pairs (46 total)
What are chromosomes made of?
DNA + Proteins
When are chromosomes duplicated?
Prior to cell division.
How is chromatin made/what is it?
DNA is wrapped around protein (histones) to make chromatin.
Material that chromosomes are composed of.
How are chromosomes moved?
Microtubules, which are organized by centrosomes.
Why is mitosis used?
Growing and healing.
Everyday cell division which occurs when a eukaryote grows and when cells need to be replaced.
Prophase (mitosis)
Chromosomes condense. - - Centrosomes push each other apart by extending microtubules between them, forming the mitotic spindle.
Metaphase (mitosis)
Chromosomes are aligned in the center of the cell.
- Each sister chromatid is attached to a microtubule through a kinetochore.
- The force applied by each centrosome aligns the chromosomes in the center of the cell.
Anaphase (mitosis)
Chromosomes separate to each side of the cell.
- The separase enzyme cleaves cohesion proteins (centrosomes separate).
- This allows for each sister chromatid to be moved to opposite ends of the cell.
Telophase/Cytokenesis (mitosis)
Chromosomes decondense and the cell splits.
- Chromosomes decondense allowing gene expression to resume.
- New nuclear envelope form from the fragments of the old envelope and the endomembrane system.
- Microtubules from the mitotic spindle are digested.
Interphase (mitosis)
Prior to Mitosis the DNA is duplicated (s phase)
- Sister chromatids are held together by cohesion proteins at the centromere.
- The centromere also duplicates forming 2 microtubule organizing centers.
Difference between telophase and cytokenesis
Cytokinesis - The cell membrane divides the cell into two new cells
Telophase - The final stage of nuclear division in mitosis or meiosis, resulting in the reformation of two distinct nuclei within the cell.
Difference between mitosis and meiosis.
of Daughter Cells
Two daughter cells in mitosis and 4 daughter cells in meiosis.
Mitosis creates clones, meiosis creates different genetic copies from each other and parent cell.
Diploid Chromosome Number:
Mitosis preserves the diploid chromosome number. The parent cell is diploid (2n), and the daughter cells are also diploid (2n). Meiosis reduces the chromosome number to half. The parent cell is diploid (2n), while the resulting daughter cells are haploid (n).
Genetic Diversity:
Mitosis does not introduce genetic diversity because the daughter cells are genetically identical to the parent cell. No crossing over occurs.
Meiosis introduces genetic diversity through the processes of crossing over during prophase I, independent assortment of chromosomes during metaphase I, and random segregation of homologous chromosomes during anaphase I and anaphase II.
Meiosis is between gametes (sex cells).
Mitosis is somatic body cells for growth and replication.
What is switched between homologous chromosomes during meiosis?
Alleles, adds even more genetic diversity to sexual reproduction.
Homologous chromosome
Homologous chromosomes, often referred to as homologs or homologous pairs, are a pair of chromosomes in a diploid organism that have the same genes in the same order but may have different alleles (versions) of those genes. In other words, homologous chromosomes are similar in structure and function, and they carry corresponding genetic information.
What is different between maternal and paternal chromosomes?
Paternal and maternal chromosomes are two categories of homologous chromosomes in diploid organisms, and they differ in terms of their origin and the genetic information they carry.
What is the difference between two homologous chromosomes?
Different alleles that encode for different genetic information about the same trait.
Homologous recombination (crossing over)
Exchanges DNA between homologous chromosomes.
Photosystems 1 and 2
PSII and PSI are both vital components of the photosynthetic process, working together to capture light energy, convert it into chemical energy, and generate ATP and NADPH for the synthesis of sugars and other organic molecules in plants and photosynthetic microorganisms.
