1
Q
Three elements make up 96% of the dry mass of the plant:
A
- Carbon
- Hydrogen
- Oxygen
2
Q
The remaining 4% of the dry mass is composed of Six
additional elements (considered “macronutrients”).
They are obtained from the soil.
A
- Nitrogen: N (NO3- or NH4+)
- Potassium: K+
- Calcium: Ca2+
- Magnesium: Mg2+
- Phosphorous: H2PO4-
- Sulfur: SO42-
3
Q
What happens when a mobile nutrient is in short supply
A
N, K, P, and Mg can be readily transferred from older leaves
to newer leaves when in short supply:
Scarcity is reflected in deterioration of older leaves
4
Q
What happens when an imobile nutrient is in short supply
A
Ca and Fe remain tied up in older leaves:
Scarcity is reflected in deficiency symptoms in newer leaves
5
Q
what is the best kind of soil for plants
A
Loamsbest soil for plants, contain equal amounts of sand,
slit, and clay along with high proportions of humus (dark, organic material in soil formed when plant and animal matter fully decomposes)
6
Q
Elements required for plant growth occur in the soil as…
A
ions (ions are electrically charged particles), in elemental or molecular ion form
7
Q
Anions
A
- ions with negative charges, interact with water
molecules via hydrogen bonding: - As solutes, anions are readily available to plants for
absorption but are easily washed out of soil by rain
*
8
Q
Cations
A
- ions with positive charges:
- Dissolve in soil water but are not immediately available because they interact with negative charges found on soil particles:
1. Organic matter that is rich in negatively charged organic acids
2. The surfaces of clay particles that are rich in mineral
anions
8
Q
leeching
A
Loss of nutrients via movement of water through soil is
called leaching
9
Q
cations bind to…
A
clay particles and organic
matter
10
Q
anions bind to…
A
Anions tend to stay in
solution (do not bind)
11
Q
Change in pH of soil causes what?
A
Cation exchange releases nutrients bound to soil
particles;
12
Q
Nutrient depletion
forces
A
continual
root growth.
13
Q
how do Ions enter roots?
A
along electrochemical gradients created
by the root using proton pumps
a). protien pumps establish an electrochemical gradient
b). cations enter root hairs via channels
c). Anions enter roothairs via cotransporters
14
Q
What are Mycorrhizal Fungi ?
A
mutualistic and aid
plants in nutrient
scavenging (>95% of all
plants have them)
Greatly increases the
surface area for nutrient
scavenging and
absorption.
15
Q
Passive Exclusion is what?
A
is when a plant prevents harmful substances (like toxic ions or excess salts) from entering its roots without using energy.
16
Q
Where does passive exclusion occur?
A
Occurs at the Plasma Membrane by
absence of channels or carriers
17
Q
what is active exclusion?
A
Active exclusion is when a plant uses energy (ATP) to actively prevent harmful or excess ions from entering its cells — or to pump them back out.
18
Q
how does active exclusion work?
A
- H⁺ (protons) move one way (usually down their concentration gradient)
- Na⁺ (sodium) moves the opposite way (often against its gradient)
- This helps plants:
- Remove excess sodium
- Maintain proper pH balance
- Survive in salty soilsOne substance moves into the cell
- Another substance moves out of the cell
- The movement of one helps power the movement of the other
19
Q
How does Active Exclusion neutralize ions
A
20
Q
Nitrogen Fixation
A
Nitrogen gas(N2 )
2N :
Makes up 80% of the atmosphere
Plants and other eukaryotes cannot use nitrogen in this form2N
is unreactive; great deal of energy needed to
break its triple bond
Plants absorb nitrogen such as ammonium( )
4NH +
or nitrate ions( )
3NO :−
Plant growth often limited by availability of usable nitrogen
21
Q
Where do
Nitrogen-Fixing Bacteria Live
A
In Some Plants, Roots Form Nodules
22
Q
How does Symbiotic Bacteria do nitrogen fixation
A
Species of bacteria and archaea absorb N2 and convert it
to NH3, NO2 or NO3
23
Q
Nitrogen fixation uses what kind of enzymes
A
equires series of specialized enzymes
and cofactors including large multi-enzyme complex called
nitrogenase
24
Where are nitrogen-fixing rhizobia found
Infected root cells of legumes form distinctive nodules where nitrogen-fixing rhizobia (beneficial soil bacteria that form a symbiotic relationship with legumes) are found:
25
What is the energy source for Nitrogen fixation
equires of 8 high-energy electrons and
16 A T P molecules for nitrogenase to reduce one molecule
of N2 to two molecules of NH3
26
Why are nodules pink
because they contain leghemoglobin,
oxygen-binding molecule similar to hemoglobin
Leghemoglobin protects nitrogenase, which is poisoned
by oxygen, by maintaining low levels of free oxygen
27
What is the first infection event
Young roots release compounds called flavonoids:
Tend to attract rhizobia
When rhizobia contact the flavonoids, they produce
Nod factors:
Nod factors bind to signaling proteins on membrane
surface of root hairs
28
Epiphytic Plants
they often grow on the trunks or branches of trees. For this reason they are called epiphytes (“upon-plants”). Epiphytes are not parasitic.
* they often grow on the trunks or branches of trees. For this reason they are called epiphytes (“upon-plants”). Epiphytes are not parasitic.
* dont affect fitness of host
29
Parasitic Plants
Parasites
are organisms that live in close physical contact with individuals from another species and that lower the fitness of those individuals, usually by obtaining water or nutrients from the host.
30
carnivorous plants
Parasites
are organisms that live in close physical contact with individuals from another species and that lower the fitness of those individuals, usually by obtaining water or nutrients from the host.
* hese results suggest carnivory is a trait that shows phenotypic plasticity
* Plants increase investment in prey-capture structures when nitrogen is rare, but they decrease investment in such structures when nitrogen is readily available.
31
Soil texture matters because it affects:
Root penetration
Water holding capacity
Oxygen availability
32
How Roots Influence Soil pH
Roots release H⁺ (protons).
This:
Displaces cations from soil particles
Causes cation exchange
Makes nutrients available
(Page 19)
33
How Plants Absorb Nutrients & Prevent Toxins
Roots use ATP-powered proton pumps to:
Create electrochemical gradients
Drive ion uptake
(Page 22)
Cations enter via channels
Anions enter via cotransporters
34
Passive & Active Control of Toxins
* Passive exclusion:
Absence of channels prevents entry
* Active exclusion:
Antiporters move Na⁺ into vacuoles
(Page 25–26)
* Metallothioneins & phytochelatins:
Bind toxic ions inside cells Neutralize them
35
How Bacteria Infect Legumes
Roots release flavonoids
Rhizobia produce Nod factors
Nod factors bind to root hair receptors
Nodules form
(Page 33 & 30)
Nodules contain:
Rhizobia
Leghemoglobin (pink)
Protects nitrogenase from oxygen
36
Autotroph vs. Heterotroph
Autotroph: Makes its own food (e.g., plants using sunlight).
• Heterotroph: Must consume other organisms for energy (animals).
37
38
Major Nutrients Important to Animals
Carbohydrates
• Proteins
• Lipids
• (Plus vitamins, minerals, and water — though not shown on that specific slide)
39
Mouthparts
Saber-toothed cats → Large canines for stabbing/slicing (carnivore).
• Snakes → Flexible jaws to swallow prey whole.
• Humans → Mixed teeth (omnivores).
Structure reflects diet type.
40
Mouth
Mechanical + chemical digestion (salivary amylase)
41
Esophagus
Transports food
42
Stomach
Mechanical mixing + protein digestion
43
Small intestine
Chemical digestion + absorption of AA
44
Large intestine
Water absorption + gut microbes
45
Liver
makes bile
46
Gallbladder
Stores bile
47
Pancreas
Secretes digestive enzymes
48
differences in digestive tracts btw animals
Cows (herbivores) → Larger fermentation chambers.
• Birds → Gizzard for grinding.
• Snakes → Expandable stomach.
• Carnivores → Shorter intestines.
49
Carbohydrates
* difested in Mouth, Small intestine
* Salivary amylase, Pancreatic amylase, Lactase/Maltase
* Absorption:Monosaccharides → bloodstream
50
Proteins
* Digested: Stomach, Small intestine
* Enzymes:Pepsin, Trypsin & other proteases
* absorption:Amino acids → bloodstream
51
Lipids
Digested by:Small intestine
Enzymes:Bile + Pancreatic lipase
Absorbed:Fatty acids → lymph → bloodstream
52
Bile vs Lipase
Bile: Emulsifies fats (breaks large droplets into smaller ones).
Lipase: Chemically digests triglycerides into monoglycerides + fatty acids.
Bile = physical breakdown
Lipase = chemical breakdown
53
Why the Stomach Produces Acid
Stomach produces HCl:
Activates pepsinogen → pepsin
Kills bacteria
Creates acidic environment for protein digestion
Parietal cells use a proton pump (ATP) to secrete H⁺ into stomach lumen.
54
Blood Glucose Negative Feedback Loop
If glucose is HIGH:
Pancreas releases insulin
Cells take up glucose
Liver stores glucose as glycogen
Blood glucose decreases
If glucose is LOW:
Pancreas releases glucagon
Liver breaks glycogen → glucose
Blood glucose increases
Maintains homeostasis.
55
Type 1diabities
* caused by no insulin production
* happens in young ppl
* tx: insulin injections
* prevalance: less comon
56
Type 2 diabeities
* Cause: insulin resistance
* age: middle aged
* tx: diet, exersize, drugs
* Prevalance: more common
57
Appendix
Contains immune tissue;
harbors symbiotic bacteria
58
Cerebrum
responsible 4: Conscious thought
Sensory perception
Voluntary movement
Learning & memory
59
frontal lobe
decision-making, personality, motor control
60
Parietal
sensory processing
61
Occipital
vission
62
temporal
hearing and memory
63
Diencephalon
Homeostasis (includes hypothalamus)
Hormone regulation
Relay center (thalamus)
64
Brain Stem
Basic life functions (breathing, heart rate)
Connects brain to spinal cord
65
Cerebellum
Balance
Coordination
Fine motor control
66
Neuroplasticity
the brain’s ability to change structure and function.
* Example: Learning strengthens synapses.
SRIs (Prozac slide 16–17) increase serotonin signaling and may promote neurogenesis.
67
Neurogenesis
new neurons formed (songbirds’ brain regions grow in spring)
68
Neuronal migration
neurons move to new locations
69
Synaptogenesis
formation of new synapses
70
Synaptic plasticity
strengthening/weakening of synapses
71
Central Nervous System (CNS)
Brain + spinal cord
Information processing
72
Peripheral Nervous System (PNS)
Afferent division and efferent divission
73
Afferent division
Sensory input → CNS
74
Efferent division
somatic and autonomic responses
75
somatic response
voluntary control
76
autonomic
involuntary control
Sympathetic → fight or flight
Parasympathetic → rest and digest
77
Dendrites
receive information
78
Cell body (soma)
integrate signals
79
Axon
propagate action potential
80
Axon terminals
transmit to next cell
81
Information flow in a neuron
Dendrites → Soma → Axon → Synapse
82
Resting Membrane Potential
Resting potential ≈ –65 mV
83
How is resting membrane potential established
Unequal ion distribution (Na⁺ outside, K⁺ inside)
K⁺ leak channels
Na⁺/K⁺ pump
Negatively charged proteins inside cell
Inside is negative relative to outside.
84
Action Potential in neurons
Resting potential
Threshold reached
Depolarization → voltage-gated Na⁺ channels open → Na⁺ rushes in
Repolarization → Na⁺ channels close, K⁺ channels open
Return to resting
85
Propagation:
Depolarization spreads down axon
In myelinated axons, action potentials “jump” between nodes of Ranvier (saltatory conduction)
(Slide 14)
86
Voltage-gated channels
Open in response to membrane potential changes
Important in action potentials
Voltage = electrical trigger
87
Ligand-gated channels
Open when neurotransmitter binds
Found at synapses
Ligand = chemical trigger
88
Synaptic Transmission
Action potential reaches presynaptic terminal
Neurotransmitters released
Neurotransmitters cross synaptic cleft
Bind receptors on postsynaptic membrane
Ligand-gated channels open
New signal generated
89
How plants detect and respond to environmental stimuli
Sensory cells detect stimulus (light, gravity, touch).
Signal is transduced into an internal signal.
Target cells respond → growth or movement.
Plants use hormones (especially auxin) as signaling molecules.
90
How cells process sensory information
Signal transduction pathway:
Receptor activated
Phosphorylation cascade (ATP used)
Ca²⁺ second messenger release
Gene transcription changes or membrane protein changes
This amplifies the signal.
91
How cells respond to hormones
Hormones bind receptors → trigger:
Gene expression changes
Cell elongation
Cell division
Ion channel activity
Example: Auxin causes differential growth in phototropism (Slides 12–19).
92
4. Phototropic growth response
Light sensed at coleoptile tip
Hormone moves downward
Lower cells elongate
Plant bends toward light
93
Blue light and phototropism
Plants bend specifically in response to blue light.
94
Role of auxin in phototropism
Auxin redistributes to shaded side
Cells on shaded side elongate more
Plant bends toward light
Agar experiments confirm auxin diffuses as chemical signal.
95
Phytochrome and Red/Far-Red Light
Phytochrome exists in two forms:
Pr (absorbs red light ~660 nm)
Pfr (absorbs far-red light ~735 nm)
Red light:
Pr → Pfr → germination
Far-red light:
Pfr → Pr → no germination
This is photoreversible (Slide 31–32).
The ratio of Pfr/Pr determines:
Seed germination
Stem elongation
Flowering (Slide 33–36)
96
Gravitropism
Statoliths (amyloplasts)
Starch-filled organelles
Settle at bottom of root cells
Detect gravity
Auxin role in roots
Gravity causes auxin redistribution
Higher auxin on lower side
In roots, auxin inhibits elongation
Root bends downward
(Important: opposite effect of auxin in shoots.)
97
Physical Forces & Touch in cells
Thigmotropism:
Plants respond to touch
Tendrils coil
Venus flytrap closes via action potentials
Cells swell to trap prey
98
Auxin
elongation, apical dominance
99
Gibberellins
stimulate growth & seed germination
100
Jasmonic acid
defense response
101
Systemin
herbivore response
102
Ethylene
(implied in senescence topic)
103
Abscisic acid
(ABA) (comparison objective)
104
Auxin & Apical Dominance
pical meristem produces auxin
Auxin suppresses lateral buds
Removing tip → lateral shoots grow
105
Cytokinins & Cell Division
Cytokinins:
Promote cell division
Work with auxin to regulate growth patterns
106
Gibberellins (GA):
Stimulate growth
Trigger α-amylase production in seeds
Promote germination
107
Abscisic Acid (ABA):
Promotes dormancy
Opposes GA
Involved in stress responses
108
Brassinosteroids
Promote cell expansion
Affect plant body size
109
Ethylene & Senescence
Ethylene:
Promotes fruit ripening
Promotes aging (senescence)
Involved in stress responses
110
Hypersensitive defense response
Localized cell death to stop pathogen spread
SAR (systemic acquired resistance)
111
Systemin defense response
Produced after herbivore attack
Triggers jasmonic acid production
Leads to proteinase inhibitors
112
How various tastes are sensed
Taste receptors are located in papillae on the tongue.
Dissolved chemicals enter a pore.
Taste cells detect specific chemicals (salt, acid, sweet, bitter, umami).
Signal travels through an afferent neuron to the brain.
Taste = chemoreception.
113
How smells are sensed
Odor molecules dissolve in mucus in the nasal cavity.
Bind to receptors on olfactory receptor neurons.
Action potentials travel to the olfactory bulb.
Signals processed in brain (glomeruli).
Smell also = chemoreception.
114
Outer ear step 1
Sound waves enter ear canal.
Vibrate tympanic membrane (eardrum).
115
middle ear step 2
Ossicles amplify vibrations.
Stapes pushes on oval window.
116
Inner ear (cochlea) stage 3
Fluid waves bend basilar membrane.
Bending stereocilia on hair cells:
K⁺ channels open
Membrane depolarizes
Ca²⁺ enters
Neurotransmitter released
Signal sent to brain
Frequency detection:
Base (stiff) = high frequency
Apex (flexible) = low frequency
117
Structure & function of insect eye
Insect eyes = compound eyes:
Many ommatidia
Wide field of vision
Motion detection
118
Cornea
Transparent outer layer
Bends (refracts) incoming light
Provides most of the eye’s focusing power
It’s the first structure light passes through.
119
Iris
Function:
Colored part of the eye
Controls the size of the pupil
Regulates how much light enters
Muscle contraction changes pupil size.
120
Pupil
Function:
Opening in the center of the iris
Allows light to enter the eye
Gets larger in dim light, smaller in bright light
It does not focus — it controls light amount.
121
Lens
Function:
Fine-tunes focus of light onto the retina
Changes shape (accommodation)
Thick = near vision
Thin = distance vision
Works with the cornea to focus the image.
122
Retina
Function:
Contains photoreceptors (rods & cones)
Converts light into electrical signals
Begins visual processing
Layers include:
Rods & cones → detect light
Bipolar cells → relay signal
Ganglion cells → send signal to brain
123
Fovea
Small region of retina with highest cone density
Sharpest, most detailed vision
Critical for reading and fine detail
Mostly cones → strong color and daylight vision.
124
Optic Nerve
Bundle of ganglion cell axons
Carries visual information to the brain
This is where the electrical signal leaves the eye.
125
Retinal activation by light
Rhodopsin = opsin + retinal.
Retinal in cis form (inactive).
Light converts retinal → trans form.
Opsin activated.
Signal cascade begins.
cis → light → trans (active)
126
Rods
Sensitive to low light
No color
Night vision
127
Cones
Detect color
Three types (humans):
S (blue ~420 nm)
M (green ~530 nm)
L (red ~560 nm)
Color vision depends on comparing cone activity.
128
Species with stronger color or black-and-white vision
Nocturnal animals (e.g., bats) → more rods → strong black-and-white vision.
Primates, birds → strong color vision (multiple cone types).
Predators active at night → rod-dominant.
129
Ultraviolet vision
Many insects (flowers reflect UV)
Birds
130
Infrared (thermoreception)
Pit vipers (snake image)
131
Electroreception
Electric fish
Sharks
132
Magnetoreception
Migratory birds
133
Endocrine chemical signal
hormones travel through bloodstream to distant targets.
134
Paracrine – chemical signal
act on nearby cells.
135
Autocrine – chemical signal
act on same cell that released them.
136
Neurohormones chemical signal
– neurons release hormones into blood (e.g., ADH).
137
Pheromones – chemical signal
signals between individuals of same species.
138
Exocrine signaling – chemical signal
secreted through ducts (not hormonal, but chemical signaling contrast).
139
ACTH
produced: Anterior pituitary
target: Adrenal cortex
function: Stimulates release of cortisol (stress hormone)
140
FSH (Follicle-stimulating hormone)
produced: Anterior pituitary
target: Ovaries / Testes
function: Stimulates gamete production (eggs & sperm)
141
LH (Luteinizing hormone)
produced: Anterior pituitary
target:Ovaries / Testes
function: Stimulates sex hormone production (estrogen, progesterone, testosterone)
142
Hypothalamus–Pituitary Connections
Posterior Pituitary
Direct neural connection.
Hypothalamic neurons extend axons into posterior pituitary.
Hormones (ADH, Oxytocin) stored and released.
Anterior Pituitary
Connected by blood vessels (hypophyseal portal system).
Hypothalamus releases regulatory hormones into bloodstream.
These stimulate anterior pituitary.
143
Why “Master Glands”?
Because:
Hypothalamus controls pituitary.
Pituitary controls other endocrine glands.
Cascading regulation system.
144
Negative Feedback Example: HPA Axis
Example: CRH → ACTH → Cortisol
Hypothalamus releases CRH.
Anterior pituitary releases ACTH.
Adrenal gland releases cortisol.
Cortisol inhibits CRH and ACTH.
This is negative feedback inhibition.
145
Peptides/Polypeptides (hormone)
example:Insulin
receptor location: plasma memberane
-water soluble
146
Amino acid derivatives (hormone)
example:Epinephrine
receptor location: plasma membrane
-water soluble
147
Steroids (hormone)
Example: cortisol and testosterone
receptor location: intracellular
-lipid souble
148
Steroid Hormones from Cholesterol
Steroids derived from cholesterol backbone.
Testosterone can be converted to estradiol via aromatase.
Estrogen formed by modifying testosterone structure.
149
Best Experimental Design for Hormone Action
Strong design includes:
Removal of hormone source (castration)
Reimplantation control
Comparison groups
Demonstrating bloodstream transmission
Controls + manipulation + replication = robust design.
150
Endocrine Disruption
Definition:
Chemicals that interfere with hormone signaling.
Examples:
Synthetic steroids
Environmental estrogens
BPA
Pesticides
They may mimic hormones or block receptors.
151
Water-soluble hormones
Bind receptor
Activate G-protein
cAMP cascade
Amplificatio
152
Bio 162
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