Bio 173 - Exam #1 Textbook Assigned reading notes

4/1/24 - Section 1.2 & 33.3

• Chemical and Physical Principles

  • scientific inquiry shows that living organisms come from other living organisms

  • the living and non-living worlds follow the same chemical rules and obey the same physical laws

    • 1st law of thermodynamics, 2nd law of thermodynamics

• Homeostasis

  • definition: the active maintenance of stable conditions inside of cells and organisms

  • can be achieved by negative feedback

    • a process in which the output or product of a pathway opposes the initial stimulus to primary maintain conditions

    • homeostasis relies on negative feedback loops to maintain a set point

4/2/24 - Chapter 6

• Metabolism

  • organisms can be classified according to their energy and carbon sources

    • phototrophs, chemotrophs → heterotrophs & autotrophs

  • metabolism is the set of chemical reactions that sustain life

    • divided into two branches: catabolism and anabolism

  • kinetic energy and potential energy are the two basic forms of energy

    • chemical energy is a form of potential energy

  • ATP is readily accessible form of cellular energy

    • the energy is held in the bonds connecting the phosphate groups

  • a chemical rxn occurs when molecules interact

    • the reaction can be reversible; can achieve chemical equilibrium or a balanced rate of forward and backwards reaction

  • the laws of thermodynamics determine whether a chemical reaction requires or releases energy available to do work

    • Gibbs Free Energy (± delta G)

    • exergonic & endergonic

    • enthalpy (delta H)

  • the hydrolysis of ATP is an exergonic reaction

  • nonspontaneous reactions are often coupled to spontaneous reactions

    • energetic coupling

4/3/24 - Chapter 7

4/4/24 - Chapter 8

4/8/24 - Section 8.4 & 8.5, 25.2 & 25.3, 29.1 & 29.2

• Challenges to photosynthesis

  • if more light energy is absorbed than the Calvin cycle can use, excess energy can damage the cell

    • a buildup of unstable energy in the electron transport chain increases the probability of creating reactive oxygen species

  • RUBSICO binds to oxygen instead of carbon dioxide

• defenses that photosynthetic organisms utilize to avoid complications with the Calvin cycle

  • high concentration of antioxidants in chloroplasts

  • preventative measures taken against the formation of reactive oxygen species

    • xanthophylls reduce excess light energy by converting the light energy into heat & is activated by low lumen pH (their activity is coupled with the electron transport chain)

• Photorespiration leads to a net loss of energy and carbon

  • the process consumes ATP & ATP is used to recycle the compounds formed when oxygen combines with RuBP

    • drains energy because it results in the oxidation and loss of carbon atoms that have already been incorporated and reduced by the Calvin cycle

    • consumes ATP

• the slow process of the Calvin cycle is a trade-off for how picky RUBISCO is to favoring environments with lower oxygen abundance

  • a key constraint for photosynthetic organisms for the trade-off of selectivity and speed

• evolution of photosynthesis

  • the ability to capture energy from sunlight is likely to have evolved in steps

    • because UV rays can damage DNA and macromolecules, an adaptation to shielding those rays effectively was implemented

  • the ability of using water as an electron donor in photosynthesis impacts:

    • where photosynthesis could take place (anywhere with sufficient sun and water to survive)

    • the hydrolysis of water leads to a proton and oxygen (donates it’s electrons)

  • eukaryotic organisms gained the ability to photosynthesize by endosymbiosis

• eukaryotic origins

  • chloroplasts are descendants of symbiotic cyanobacteria that resided in eukaryotic cells

    • genetic material between the chloroplasts (cyanobacteria) and photosynthetic eukaryotes were lost during evolution

  • mitochondria ancestry can also be traced back to bacteria

    • even if a eukaryotic cell does not contain a mitochondria, the hypothesis that mitochondria have evolved through symbiosis cannot be discarded because their nuclear genome contain mitochondria genetic material

4/9/24 - Section 30.1, 30.2, 30.3

• Primary growth of shoots (increase in length)

  • shoots exhibit modular growth - elongation of the plant by active shoot apical meristem which extends the length by producing the same unit of construction over and over & the apex of each stem is a site of rapid cell division

    • shoot apical meristems produce new cells that expand and differentiate to form the cells of the plant & initiates leaves and produces axillary buds

  • cell expansion drives the elongation of stems

    • the driving force for cell expansion is the turgor pressure that develops inside plant cells (the cell wall extends more easily in length than width)

    • cells near the shoot apex maintain their ability to divide through the expression of meristem identity genes

  • the shoot apical meristem controls the production and arrangement of leaves

    • nodes and antinodes on some plants form a recognizable pattern

  • flower development terminates the growth of shoot apical meristems

• Primary growth of roots

  • roots grow by producing new cells at their tips

  • difference of roots primary growth compared to shoots primary growth

    • the root apical meristem is covered by a root cap that protects the meristem

    • the root apical meristem does not produce lateral organs whereas the shoot apical meristem produces leaves

  • the formation of new root apical meristems allows roots to branch

  • the structures and functions of root systems are diverse in morphology

• Secondary growth (increase in width)

  • secondary growth is necessary to strengthen the stem by increasing in girth and by increasing the transport capacity of the vascular system above and belowground

  • secondary growth is the result of two lateral meristems

    • one distinct lateral meristem produced during secondary growth is vascular cambium which is the source of new xylem and phloem

    • the second distinct lateral meristem produced during secondary growth is cork cambium which renews & maintains an outer layer of protection

  • differences between lateral meristems and apical meristems

    • they are located near the periphery of stems and roots rather than at the tip

    • lateral meristems only form after primary growth so the new cells grow in diameter and not length

    • lateral meristems become larger over time because as the stem or root becomes thicker, the number of meristem cells needed to encircle the stem increases

  • the vascular cambium produces secondary xylem and phloem

    • the vascular cambium forms a continuous layer that extends around the entire length of the plant

    • the cells on the inside of this layer become the secondary xylem whereas the cells produced on the outside become secondary phloem

  • the cork cambium produces an outer protective layer

    • lenticels are small regions where the outer bark cell are tightly less tightly packed to allow for gas exchange and diffusion to occur

4/15/24 - Section 29.1 & 29.2

• Photosynthesis on Land

  • hazard of potential desiccation

    • bryophytes: mosses, liverworts & hornworts that live in proximity to a water source, dependent on their environment to whether they will wither

    • vascular plants: rely on water from the soil to maintain a more stable level of hydration

• carbon dioxide gain and water loss

  • CO2 uptake results in water loss: transpiration

  • the waxy cuticle restricts water loss from leaves but inhibits the uptake of CO2

  • stomata allow leaves to regulate water loss and carbon gain

  • CAM plants use nocturnal CO2 storage to avoid water loss during the day

  • C4 plants suppress photorespiration by concentrating CO2 in bundle-sheath cells or the immediate vicinity of RUBISCO

4/16/24 - 26.2 & 29.3

• diffusion is effective only over short distances

  • diffusion: the net movement of molecules from areas of higher concentration to areas of lower concentration due to random motion

    • exerts a strong constraint on the size, shape, and function of cells & limits the size and shape of bacterial cell