Signal Transduction and Plant Hormones

Signal Transduction Stages

• Reception happens on the plasma membrane.
• A ligand or environmental trigger links to a receptor.
• Transduction transmits a signal through relay proteins and secondary messengers.
• A cellular response is activated which could trigger gene expression or enzyme activation.

Phytochrome I Role

• Phytochrome I activates in the cytoplasm via light.
• Activated Phytochrome I opens Ca2+ channels acting as a secondary messenger for protein kinase 2.
• Secondary messenger concentration rises due to phytochrome activation, which then triggers protein kinase 1.
• The opening of the Ca2+ channels triggers protein kinase 2.
• These kinases conduct phosphorylation which is the addition of phosphate groups.
• Protein kinases then trigger transcription factors in the nucleus.
• These transcription factors get translated into de-etiolation responses of proteins.

Auxin Role

• Auxin can start cell elongation.
• As per the acid growth hypothesis, auxin triggers proton pumps in the plasma membrane to lower the pH in the cell wall, which then activates expansins. Expansins loosen the cell wall which allows for elongation.

Ethylene Role

• Ethylene responds to mechanical stress to avoid the stress
• It also triggers ripening, which then triggers more ethylene release.

Gibberellins Role

• Gibberellins encourage seed and bud germination.
• It encourages stem elongation and leaf growth.
• Gibberellins also encourage flowering and fruit growing.

Plant Defense Methods

• Pathogen-Associated Molecular Patterns (PAMPs) is the first line of defense.
• PAMPs recognition signals the production of antimicrobial chemicals and toughening of the cell wall.
• Hypersensitive Response causes cell/tissue death near the infection by causing enzyme production.
• This stimulates cell wall changes which confine the pathogen.
• Systemic Acquired Resistance leads to defense gene expression and is long lasting.
• Methyl salicylic acid is made around the infection spot.
• It moves in the phloem to remote sites to become salicylic acid to then trigger defenses against infections.

Seed Germination

• Seed germination needs gibberellins.
• Water is absorbed and triggers gibberellins from the embryo.
• This signals seeds to germinate, releases amylase, and starts root and shoot growth.

Animal and Plant Challenges

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Animal Body Size and Shape

• Thicker skeletons are needed for support as animal size increases
• Internal systems must also change.

Tissues & Fluids Defined

• Tissues: specialized cells that are organized and have distinct jobs.
• Organs: Tissues form organs, and organs make up an organ system.
• Interstitial Fluid: the fluid-filled gaps between cells.

Animal Tissue Types

• Epithelial covers the outside of the body and lines organs/cavities containing different cell shapes w/different functions.
• Simple: Single cell layer
• Stratified: Multiple cell tiers
• Pseudostratified: A single layer of cells of varying length
• Connective Tissue has sparsely packed cells scattered through an extracellular matrix.
• Fibroblast secretes the protein of extracellular fibers
• Macrophages are part of the immune system
• Muscle Tissue enables body movement
• Actin & Myosin enable muscle contraction
• Nervous Tissue enables the receipt, processing, and transmission of information.
• Neurons communicate with each other through neurotransmitters.
• Includes Neurons and Glia

Animal Heat Sources

• Endothermic animals generate heat with metabolism.
• Birds and mammals are endotherms.
• Ectothermic animals gain heat from outside.
• Includes invertebrates, fishes, amphibians, and non-avian reptiles.

Homeostasis/Body Temp

• Homeostasis keeps a steady state regardless of the outside environment.
• Body temperature is kept with thermoregulation.
• This helps animals keep an internal temp in a reasonable range.

Feedback Loop

• Positive Feedback amplifies a stimulus and does not usually result in homeostasis in animals.
• Negative Feedback assists to restore a variable to a normal range.

Metabolic Rate/Body Size

• Metabolic rate decreases as body size increases.
• Smaller animals have a higher metabolic rate than bigger animals.

Body Thermostat

• Thermoregulation is managed in mammals by the hypothalamus.
• The hypothalamus triggers heat loss or gain.

Metabolic Rates

• Metabolic Rate calculates energy use in a period of time.
• Basal Metabolic Rate (BMR) calculates metabolic rate on an endotherm at rest at a "comfortable" temperature.

Glucose Regulation

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Food Processing Phases

• Ingestion: Food is taken in through mechanical digestion and mixed with saliva to begin digestion.
• Digestion: Food moves down the digestive tract.
• Includes mechanical and chemical digestion (enzymatic hydrolysis).
• Absorption: Nutritional molecules move into the body cells.
• Elimination: Undigested waste discharges as urine/feces.

Digestion Location

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Mammalian Processes

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Macromolecules Digestion

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Nutrient Absorbtion

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Small Intestine Specialization

• The small intestine contains pancreatic enzymes for all four macromolecules of food.
• The small intestine contains microvilli along the epithelial cells.
• This increases the surface area for greater absorption of nutrients.

Digestion Strategies

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Hormonal Regulation

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