Enzymes
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 Photosynthesis
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 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 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 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 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 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 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 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 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
Glycolysis
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 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 PLANTS
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 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 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): → 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
Unit 3: Cellular Energetics