Unit 3: Cellular Energetics

Extracellular Components
Extracellular components and connections between cells help coordinate cellular activities
Most cells synthesize and secrete materials that are external to the plasma membrane
These extracellular (outside plasma membrane) structures include
Cell walls of plants- major structural component of plant cells made of cellulose, also found in prokaryotes, protists and fungi (peptidoglycan)
Cell wall protects the plant cell, maintains its shape and prevents excessive uptake of water
Plant cell walls are made of cellulose fibers embedded in other polysaccharides and proteins
Thin Flexible Primary Cell Wall
Thick Secondary Cell Wall
In between plasma membrane and primary wall gives structural integrity
Middle lamella - material between cell walls
Plasmodesmatagaps in cell wall allowing for communication and movement of things between plant cells, rigid cell walls are restrictive unlike permeable membranes
Extracellular matrix (ECM) of animal cells instead of cell walls
Series of glycoproteins such as collagen (major), proteoglycans, and fibronectin make up ECM
Fibronectin connects collagen to integrin
Proteoglycans perform adhesion (glue)
Proteins bind to receptor proteins in the plasma membrane called integrins
Intercellular junctions physically connect cells, adhere interact or communicate through direct contact
Plasmodesmatagap-like channels that perforate cell walls
Tight Junctions membranes of neighboring cells are pressed together preventing leakage of extracellular fluid in between cells (in stomach)
Desmosomes (anchoring junctions) fasten cells together into strong sheets--strongest function (muscle cells)
Gap junctions (communicating junctions) provide cytoplasmic channels between adjacent cells (heart cells), enable multiple cells to act as one
The most important reaction in all of nature, makes food
Converts solar energy into chemical energy
Directly and indirectly nourishes all living things
Autotrophs/Producers - organisms that produce their own food through photosynthesis
Algae (protist, eukaryotic organism), plants, cyanobacteria - first living organisms to perform photosynthesis
Heterotrophs/Consumers - must eat in order to obtain energy, eating products of photosynthesis
Energy (light, invested energy) + 6CO2 + 6H2O → C6H12O6 + O2
Opposite of cell respiration (which is exergonic, produces ATP), photosynthesis is endergonic
Water is oxidized to O2, CO2 is reduced → glucose
Photosynthetic part of a plant (organ): Leaf
Holes in leaf: stomata, where water evaporates (transpiration) and CO2 enters and O2 leaves
Creates transpirational pull from roots
Xylem are cells that water travels through
Plants want water to evaporate out of the plants, no transpirational pull without evaporation
Plant would dehydrate if too much water evaporated, need to balance transpiration
Increase transpiration and dehydration
Heat (temperature)
Dryness (humidity)
STOMATA CLOSE to balance out environment with the guard cells
Calvin Cycle cannot occur (no CO2) can’t make sugar
RuBisCo can ALSO fix O2 to RuBP in place of CO2 → cant produce G3P
Wastes NADPH and ATP
C3 Plants make 3-Carbon compound, PGA in the calvin cycle
C4 Plants live in dry conditions (midwest), have adaptations to prevent photorespiration → STORE CARBON DIOXIDE
Doesnt matter if stomata are closed or open
Used stored CO2,
C4 Plant
Uses enzyme PEP Carboxylase → pulls in CO2 stores carbon as 4 carbon molecule Oxaloacetate
Calvin cycle takes place in Bundle-sheath cell, but still have mesophyll cells
CAM Plant - the extremes (cacti, desert plants)
Store carbon as crassulacean acid, organic acid
CAM Plant opens stomata at night (when it cools down)
More stomata on bottom, if more on top plant would dehydrate
Guard cells: flank stomata, control if stomata are open, closed, where gasses enter and leave, (O2/CO2), water can evaporate out of the stomata → transpiration (transpirational pull)
Mesophyll- part of a leaf that contains lots of photosynthetic cells
Cells contain chloroplast - double membrane, inside are pancake shaped discs called thylakoids, and stacks of thylakoids = granum
Fluid in membrane outside thylakoids called stroma
Two reactions:
Light Reactions - light (photo) inside the thylakoids
NADP+ and ADP + P, take H2O and oxidize it, produce NADPH, and ATP, O2 as a byproduct,
Light to make ATP - photophosphorylation
Calvin cycle (The Dark Reactions)- synthesis (builds molecule) inside stroma
Major reactant in cycle: CO2 reduced and given electrons/protons, creates glucose, given by NADPH gives CO2 the electrons/protons. Electrons - energy
Powered by ATP
Purpose of producing glucose?
Glucose is used for everything:
Sugar → cell respiration, used to make ATP to grow plant
Sugar = structure, cellulose (long chain of glucose)
Sugar = energy storage, starch
Light - electromagnetic radiation
Shorter wavelength -- high energy (UV, gamma, X ray)
Longer wavelength -- low energy (infared microwaves, radiowaves)
Different colors correspond with different wavelengths, visible light in the middle of spectrum
Chlorophyll a is the main photosynthetic pigment
Accessory pigments such as chlorophyll b broaden the spectrum used in photosynthesis
Xanthophylls - yellow
Carotenoids - orange
Reflect (bounce off) vs Transmitting (go through)
No light is absorbed by cell
Green light cannot be used by plant, would die
Plants absorb red and blue light the best
Color of sky depends on molecular composition of atmosphere
Spectrophotometer - put sample of light in, tells level of transmittance or absorption
Shoot green light through chlorophyll, high transmittance (low absorption)
Shoot blue light through chlorophyll, low transmittance (high absorption)
Absorption Spectrum - graph plotting a pigment’s light absorption versus wavelength
Larger spectrums,
Action Spectrum - profiles the relative effectiveness of different wavelengths of radiation in driving a process, totality of spectrums
Pigment - molecule that will absorb or reflect a wavelength
Color determined by what it reflects
Trees go dormant in winter, chlorophyll dies, only see carotenoids and xanthophylls (yellow + orange), not enough sunlight
Engelmann’s Experiment
Grew algae under different wavelengths
Grew aerobic bacteria on top of the algae, large growth on opposite sides of spectrum, none in green because algae isn’t photosynthesizing there
Plants not black because would absorb every wavelength, overheat, proteins denature
Chlorophyll has a Magnesium center (a vs. b has difference of one func. group)
Mg holds on to electrons, electrons from water and NADPH
Accepts unit of light - photon, excites electron, gives power to electron
Cellular Respiration

Alcohol fermentation (yeast)
Pyruvate converted to ethanol (2 carbon, releases CO2)
Brain cells = purely aerobic
Obligate anaerobes = die in the presence of O2 (bacteria), carry out fermentation/anerobic respiration
Denitrifying bacteria
Anaerobic respiration: use sulfates as final electron activity instead of O2 and substrate level phosphorylation not the electron transport chain
Oldest process
Before mitochondria, glycolysis took place
Oldest prokaryotes used this for energy
Cell respiration
Regulated by feedback inhibition
When ATP builds up, pathway is turned off
Utilizes allosteric enzymes
Turns off Phosphofructokinase (first enzyme in pathway)
AMP turns back on, forces pathway on

Fats and proteins can also be used in cellular respiration (triglycerides), not just glucose and carbohydrates
Fats provide more energy than carbohydrates, therefore more ATP
Glycerol (3 carbon molecule) and three fatty acids
Monomers of fatty acids/glycerol can enter cellular respiration
Glycerol has the same amount of carbons as a glucose pyruvate, enters process at pyruvate oxidation no need for glycolysis, more energy
Beta Oxidation
Fatty acids from lipids need to break down long chains of carbons in order to enter cellular respiration
Breaks the fatty acid chain and breaks it down into two-carbon molecules
Feeds directly into the Kreb Cycle
If you don’t have enough carbs or lipids, or too much protein, protein can be used in cellular respiration
Proteins have an atom that cannot enter cellular respiration, have to get rid of nitrogen in order to enter, stomach and small intestines break down proteins into amino acids
The amino acids can go into cellular respiration
The process by which the amino group (NH2) leaves the amino acid to enter cell respiration
Amino acid can enter multiple levels of the cellular respiration
Cellular Respiration refers to both aerobic and anerobic respiration but is mainly the aerobic respiration
Respiration usually tracked with glucose because it starts at the first step
Fermentation partial degradation of sugars that occur without O2
Keeps pyruvate happening?
Aerobic respiration consumes organic molecules and O2 and yields ATP
Anerobic Respiration similar to aerobic respiration but consumes compounds other than O2
Glycolysis occurs whether or not O2 is present
All plants evolved from a type of green algae called carophycenes, but modern plants are different (derived character) they can live on land
Evolutionary History: chronologically
Bryophytes: mosses, first group to evolve
Pteridophyta: ferns
Vascular Tissue: next derived character (xylem= water transport, phloem=sugar transport)
Evolution of Seed Plants: (MAJOR)adaptation that allows plants to no longer rely on water to reproduce → reproduce on land more
Gymnosperms: use cones as a reproductive structure, rely on wind to carry pollen from cone to cone
Angiosperms (flowering plants): produce flowers (reproductive structure)
Alternation of Generations:
Every generation plants flip between haploid to diploid and then back
Sporophyte: (2n) goes through meiosis to make haploid spores
Gametophyte: (n) goes through mitosis to make gametes, create a diploid zygote
In ANGIOSPERMS, the sporophyte version is dominant whereas the gametophyte is extremely reduced
The Flower: used to reproduce in angiosperms, help from animals, wind, and insects to transport pollen, brightly colored to attract other animals/bugs to it
Nectar: sugary substance produced by flowers to attract birds and bees to consume, the pollen will stick to the animals so pollen can go from plant to plant
Contains both male and female reproductive parts (lilies) but most flowers are either male or female
Stamen: male reproductive part
Anther: structure that produces pollen, flower is the sporophyte, whereas pollen produced has two male gametophytes (sperm)
Filament: long stalk that comes out of the anther
Carpel (pistil): female reproductive part
Stigma: sticky part where pollens gets stuck (top)
Style: long tube that connects to the ovary
Ovary: contains the ovule (inner structure) which produces/contains the female gametophyte (egg)
Contains a lot of a small eggs, but one big giant egg with polar nuclei (two nuclei)
Sepals: leaves beneath the flower
Petals: colored part to attract organisms with pollen
Cross-Pollination: gives genetic variation, pollen of one flower goes to the carpel of another flower
Self-Pollination: staying within the same flower anther sperm goes directly into the stigma, no genetic variation → can survive on its own without other individuals in the population (e.g. polyploidy)
Double-Fertilization: (used in angiosperms) pollen goes from male anther to female stigma, it grows a pollen tube down the style into the ovary into the ovule
Essentially, two sperm from pollen enter the ovary and fertilize two eggs
One egg in ovule (big one) contains two nuclei (polar nuclei), two sperm (from pollen) go down the tube and into the ovule, one sperm will fertilize one egg to make a zygote. The other will fertilize the big egg, to have three nuclei (triploid endosperm, functions as a food source for the developing embryo. The Ovule becomes a seed with the endosperm and embryo. The ovary around the seed becomes a fruit
Fruit: mature ovary used to disperse seeds (sporophyte embryos)
Fruit is made to taste good so herbivores eat fruit, they cannot digest seed, so they poop out seeds everywhere, seed gets fertilizer to grow into a new plant
You eat the endosperm which is the nutritious part of the nut/seed
Any type of flowering plant produces some sort of fruit
Embryo Development:
Germination occurs when mitosis of the seed occurs (begins to grow)
Cotyledons: first seed leaves upon germination
Monocot: one leaf (smaller angiosperms, orchids, grasses, lilies) VEINS RUN PARALLEL, with fibrous root systems, cannot grow that big without a lot of support
Dicots: two leaves, bigger angiosperms, has central tap roots to grow big, branching veins in leaves (maple trees, sunflowers, beans, etc.) BRANCHING VEINS
These are the two distinct and different types of angiosperms
Nitrogen: needed to make nucleic acids and proteins
Atmospheric N2 is the greatest nitrogen reservoir, but can’t do anything with that, you need to convert it
Nitrogen-fixing Bacteria: take in N2 and convert it into ammonium (NH4)
Ammonifying Bacteria (detritivores):break down dead organisms (humus) and convert it into ammonium
Nitrifying Bacteria: convert ammonium into nitrates (NO3)
The plants can accept the nitrates and use those to build macromolecules
Nitrates are the key ingredient in fertilizer to nourish plants
Roots have lots of hair things to increase surface area for rate of exchange
Transport: movement of materials in a plant
Cell Level: nutrients from soil -> roots
Depends on water potential (ONLY USED TO MOVE WATER IN PLANTS, everywhere else it only depends on osmosis/diffusion) (pressure potential + solute potential)
The lowest the pressure can be is 0, the highest the solute potential can be is 0 (pressure is nonnegative, the solute is nonpositive)
Solute potential = -iCRT, C= concentration of solutes/molarity, more solute you have the more negative the potential becomes
Plant roots have lots and lots of sugar → really low water potential (0 pressure and high positive amount of solute), TAKES IN WATER
Since plant roots have low potential, roots will absorb water from the environment, soil has no pressure, and some low solute content, higher water potential in the soil (water moves high → low potential) so the water will move into the roots
Roots will gain pressure from the water, until the water potential on the outside EQUALs the pressure on the inside, (not when the pressure is 0 necessarily) so you add a specific amount of pressure to the roots to get the same water potential
Turgor Pressure: BEGINS movement of water up the plant that builds up in the roots forces the water up from this initial transaction
Xylem: system of tubes water moves up
Transpirational Pull (evaporation): FINISHES movement of water up the plant; pulls water through and up the plant, also works through cohesion (water stuck to water) and adhesion (water stuck to other things) as the top water molecules are pulled out the stomata, and pull up the rest through hydrogen bonding
Stomata: holes in leaves where water leaves that can open and close
Guard Cells: can open and/or close stomata
What causes an increase in transpiration rate (bad too much water loss):
Higher temperatures
Arid/dryer conditions
→ causes guard cells to close stomata to preserve water
If O2 enters the calvin cycle instead of carbon dioxide will cause photorespiration (but C4 and CAM plants can store carbon dioxide)
Short distance: water from roots into xylem tubes (turgor pressure), or sugar from leaves into phloem (active transport)
Long distance: movement of water in xylem or sugar in phloem (sugar goes down to the roots to decrease water potential, but is built in the leaves through photosynthesis), phloem and xylem run side by side
Bulk Flow/Pressure flow/Translocation: water diffuses into phloem pushes sugar down using pressure into the roots
Xerophytes: desert plants that have adaptations for arid conditions (extreme CAM plants)
Only open stomata at night
Store water inside of them
Cacti needles are leaves without surface area, prevents water from evaporating as much (and protection from eaters)
Thick cuticle: feels waxy because the wax prevents water loss (wax = hydrophobic)
Stomata are always on the bottom of the leaves to prevent water loss
Plant Defenses/Immune Systems against Herbivores: physical and chemical defenses to prevent eating
Physical: thorns, trichomes (irritating hair things), prevent them from being eaten
Chemical: (poison ivy) release toxins
Chemicals in the saliva of an eating caterpillar causes a signal transduction pathway in the plant, plant releases volatile attractants to attract parasitoid wasps to kill the caterpillars and reproduce in them
Plant Defenses/Immune Systems against Pathogens: against organisms that can infect the plant
Virulent Pathogen: (viral lytic cycle) would kill the plant entirely
Avirulent Pathogen: the plant has a chance to defend itself and live (THIS defense system only works for this type of pathogen)
Gene-for-gene recognition:
R-genes: code for R-proteins that can activate plant immune system
Hypersensitive Response: causes cell and tissue death near the infection site → LOCALIZED, not across the entire plant, kill everything that is infected to save the rest of the plant, create changes in the cell wall of plant cells to confine the pathogen
Produced chemicals that can kill the specific pathogen
Systemic Acquired Resistance: spreads across the ENTIRE plant, causing the plant to become resistant to the virus (long term).
Salicylic Acid: chemical ligand that initiates SAR, (aspirin), spreads throughout the entire plant to make plant immune to that specific pathogen

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