Grade 12 Biology

this one isn’t a real study doc, just a collection of Jiao’s impromptu lectures :)

Plants v2 Lesson 03/31

I. Tropisms

1. Tropism = The way a plant responds to specific stimuli
   1. light and gravity
   2. positive = agreeing with stimuli, negative = opposing stimuli
   3. positive phototropism = growing towards sunlight; negative = growing away from light
2. Phototropism = responding to light
   1. Most plants want to be positive (more light energy for photosynthesis)
   2. All cells in the plant try to go towards
   3. All shade cells produce auxin in dark areas, which makes them want to go towards
      1. Releases H+ into plant cells, making it more acidic, loosens cellulose so when water rushes in, stretches cell towards the light permanently (like the p word)
      2. Auxin is killed by light
3. Gravitropism = responding to gravity
   1. Roots exhibit positive gravitropism; stem/leaves exhibits negative

II. Growth

1. Meristems are the cells that grow
2. Primary (apical) = length
   1. Found in places that need vertical growth (eg. roots, tips of shoots)
   2. Unspecialized cells inside the meristem undergo aggressive mitosis 
   3. New cells undergo vacuolation = poking a bunch of holes
   4. They specialize and become root / stem / etc cells
3. Secondary (lateral) = girth
   1. Cambium = Adding to tissue 
   2. Cork Cambium = Adding to bark
   3. Important for perennial plants, because they still need to survive in the winter
4. Micropropagation = making plants
   1. Unspecialized cells in the meristem can be harvested 
   2. Adding agar, auxin to DIY your own plants
   3. If there’s one problem with that plant, it affects them all
   4. Can be used to resist viruses

III. Reproduction

1. Pollination
   1. Animals carry sperm from one plant to another (or wind, water)
   2. Plants have weird adaptations to attract pollinators
      1. rafflesia arnoldii is built to look like raw meat and smell like rotting flesh
2. Fertilization
   1. Sperm goes on a long journey from antennae through tube to the egg (in an ovum in middle)
   2. Flower pollen is just sperm :)
3. Seed dispersal
   1. Seed tries to get super far from the parent plant for resources (dandelion fluff, helicopter seeds, pinecones, animals shit it out, exploding seeds)
4. Germination
   1. Germination is the process in which an organism sprouts from a seed or a spore. It is affected by a multitude of factors including temperature, water, exposure to light, and exposure to oxygen. Germination occurs when the hypocotyl emerges from the seed, causing the radicle to elongate into what will eventually become the root (Joshi, 2018). For this to occur, the seed must first undergo the imbibition of water where water fills the seed. After this, the water will activate enzymes in the seed, causing it to swell and the radicle to break through the endosperm which covers it. (Mischa, 2021) (Zhang, 2022)
   2. Forms gibberellin which produces amylase, which breaks down starch into maltose
      1. Water - gibberellin - amylase - maltose - glucose
      2. glucose - energy for future
      3. glucose - cellulose for cell wall
   3. Simultaneously, lipids and proteins undergo hydrolysis to become enzymes, phospholipids, triglycerides as plant food until it can do photosynthesis
      1. Until the bean pokes through

IV. Photoperiodicity

When do plants flower?

1. Phytochrome = photoreceptor that changes in response to light
   1. PR 
   2. PFR
   3. When exposed to daylight, PR → PFR; when exposed to darkness, vice versa
2. Types of blooming plants
   1. Long day = max amount of darkness to still bloom (summer)
      1. need a lot of PFR
   2. Short day = min amount of darkness to still bloom (winter)
      1. need a lot of PR
3. You can trick plants to bloom by giving them darkness / light
4. This is done to petunias during Easter, roses during Valentines, 

Plants Lesson 03/10

Topics

1. Water (key)
2. Minerals
3. Sugar

Tubes (both transfer water), creates a loop, blub blub blub

1. Xylem: transports mineral ions
2. Phloem: transports sugars

Xylem

1. Minerals go from soil → roots
   1. Diffuse into them bc nothing’s in the roots
   2. Mass transport of water-carrying molecules (adhesion)
   3. Fungi around the roots help (using their spindle-y roots, trade offer)
   4. When concentration becomes too high: Protein pumps use active transport
2. Water osmosis into roots
   1. Roots → Xylem → Leaves → Evaporation
3. Water Roots → Xylem
   1. Symplastic: through cells, into cytoplasm
   2. Apoplastic: around cells, into cell walls (and other intercellular spaces)
4. . Leaves → Evaporation
   1. Goes into air sacs → diffuses into stomata
   2. Area of negative pressure, causing new water to rush in
   3. This is because water is polar → cohesive and adhesive
   4. Sticks to capillary walls and itself → pulling itself up, continuous suction
5. Factors that impact this
   1. Hotter - faster
   2. Humid - less
   3. Plant losing water rapidly - Abiscics acid close stomata to stop evaporation

Phloem

1. Leaves photosynthesize
   1. Creating glucose, fructose, sucrose, some stored as starch
   2. Producers = source; Users = sink
   3. Same thing: low concentration water, high concentration sugar
   4. Water goes from Xylem → Phloem
   5. Force of the water rushing over pushes sugars over
   6. Transformation UP, translocation ANY DIRECTION
2. Other cells that help this
   1. Phloem are made of sieve cells (alive) which can do active transport, while Xylem cells are dead (passive)
   2. Companion cells :) move sugars from source to sieve cells
   3. Carrier proteins help move sugar from companion cells to sieve cells
   4. Co-transporter cells move from companion to sieve cells
3. In the Xylem, there are new minerals
   1. Water flows back into the Xylem, creating a loop
   2. That’s why sap (water + sugar + minerals) has a pressure gradient (loop)

Questions

1. Why have cells evolved in this way?
   1. Passive transport
   2. Phloem have no nuclei, thus no barriers to stop the water
   3. Nuclei go into companion cells (strategically) to produce ATP
2. What happens to a dry plant?
   1. Rolls up its leaves
   2. Thick layer of wax on leaves to stop evaporation
   3. Plants in salt water have a place in their leaves to spit out salt
   4. Plants in wet areas do the opposite → big leaves for evaporation

Breathing Lesson 02/25

Breathing

• tidal volume: air in = air out
• inspiratory reserve volume: double breath in
• expiratory reserve volume: double breath out
• residual volume: amount of air left
• lung capacity: TV + IRV + ERV
• breaths are measured with a spirometer

Gas exchange: lung → blood, tissue → blood

• High CO2, lungs → blood 
• High O2, blood → tissue

How you breathe

• Alveoli in lungs (sacs), Diaphragm
• Boyle’s Law: p1v1 = p2v2
• To inhale: Diaphragm contracts, expanding volume, lowering pressure, oxygen comes in
• To exhale: Diaphragm relaxes, decreasing volume, increasing pressure, oxygen leaves
• Could also contract abdominal muscles

When to breathe

• We know when to breathe with the pH in our blood
• Because CO2 (carbonic acid HCO3) and O2 (hemoglobin)
• Chemoreceptors tell the medulla oblongata to breathe

Hemoglobin carries oxygen 

• 4 lobes - each has Fe, binds to O
• They change their shape so Oxygen gets in easier (cooperative binding)

Carbon dioxide transported in blood

1. CO2 + H2O → H2CO3
2. H2CO3 → HCO3- + H+
3. HCO3- + Na+ → NaHCO3 (not baking soda)
4. NaHCO3 goes into lungs and gets exhaled

Erythrocyte - liquids which contain red blood cells

• HCO3- is in this liquid and must go into the RBC
• Leaves an empty space which gets filled with Cl- which keeps the liquid uncharged
  • Chloride shift
• H+ from step 2 makes the Erythrocyte acidic and signals O2 release
• Binds with hemoglobin , creating a buffer