Enzymes work by decreasing the potential energy difference between reactant and product
Catalysts So what’s a cell got to do to reduce activation energy? – get help! … chemical help… ENZYMES GG Call in the ENZYMES!
As a result of its involvement in a reaction, an enzyme permanently alters its shape.
Enzymes vocabulary substrate reactant which binds to enzyme enzyme-substrate complex: temporary association product end result of reaction active site enzyme’s catalytic site; substrate fits into active site substrate enzyme products active site
Properties of enzymes Reaction specific – each enzyme works with a specific substrate chemical fit between active site & substrate – H bonds & ionic bonds Not consumed in reaction – single enzyme molecule can catalyze thousands or more reactions per second enzymes unaffected by the reaction Affected by cellular conditions – any condition that affects protein structure temperature, pH, salinity
If a patient in a hospital was accidentally given an IV full of pure water they would be fine because pure water is neutral so it can’t hurt us.
freshwaterbalancedsaltwater Managing water balance Cell survival depends on balancing water uptake & loss
Aquaporins Water moves rapidly into & out of cells – evidence that there were water channels protein channels allowing flow of water across cell membrane 1991 | 2003 Peter Agre John Hopkins Roderick MacKinnon Rockefeller
Cell (compared to beaker) hypertonic or hypotonic Beaker (compared to cell) hypertonic or hypotonic Which way does the water flow? in or out of cell.05 M.03 M Do you understand Osmosis…
Cellular respiration is only done by heterotrophs because autotrophs can make their own energy.
N P K … H2OH2O What does it mean to be a plant? Need to… – collect light energy transform it into chemical energy – store light energy in a stable form to be moved around the plant or stored – need to get building block atoms from the environment C,H,O,N,P,K,S,Mg – produce all organic molecules needed for growth carbohydrates, proteins, lipids, nucleic acids ATP glucose CO 2
The purpose of fermentation is to produce a small amount of energy when cells don’t have access to oxygen.
recycle NADH Alcohol Fermentation 1C 3C2C pyruvate ethanol + CO 2 NADHNAD + Count the carbons! Dead end process at ~12% ethanol, kills yeast can’t reverse the reaction bacteria yeast back to glycolysis
recycle NADH Reversible process once O 2 is available, lactate is converted back to pyruvate by the liver Lactic Acid Fermentation pyruvate lactic acid 3C NADHNAD + Count the carbons! O2O2 animals some fungi back to glycolysis
Plants use water only as a means of keeping their cells full and holding the plant itself upright.
ETC of Photosynthesis Chloroplasts transform light energy into chemical energy of ATP use electron carrier NADPH generates O 2
The second step of photosynthesis is called the dark reactions because it only happens in the dark.
Light: absorption spectra Photosynthesis gets energy by absorbing wavelengths of light – chlorophyll a absorbs best in red & blue wavelengths & least in green – accessory pigments with different structures absorb light of different wavelengths chlorophyll b, carotenoids, xanthophylls Why are plants green?
From Light reactions to Calvin cycle Calvin cycle – chloroplast stroma Need products of light reactions to drive synthesis reactions – ATP – NADPH stroma thylakoid ATP
Diagram how a gamete with 3 chromosomes could be produced with two maternal chromosomes and one paternal chromosome. (there isn’t anything wrong in this statement)
Proteins Most structurally & functionally diverse group Function: involved in almost everything – enzymes (pepsin, DNA polymerase) – structure (keratin, collagen) – carriers & transport (hemoglobin, aquaporin) – cell communication signals (insulin & other hormones) receptors – defense (antibodies) – movement (actin & myosin) – storage (bean seed proteins)
Structural homologies only exist in animals, never in plants.
Analogous structures Separate evolution of structures similar functions similar external form different internal structure & development different origin no evolutionary relationship Solving a similar problem with a similar solution Don’t be fooled by their looks!
Convergent evolution Flight evolved in 3 separate animal groups – analogous structures Does this mean they have a recent common ancestor?
Convergent evolution Fish: aquatic vertebrates Dolphins: aquatic mammals similar adaptations to life in the sea not closely related Those fins & tails & sleek bodies are analogous structures!
Bird and bat wings can only be described as homologous structures, not as analogous structures.
Transport in plants H 2 O & minerals – transport in xylem – Transpiration Adhesion, cohesion & Evaporation Sugars – transport in phloem – bulk flow Gas exchange – photosynthesis CO 2 in; O 2 out stomates – respiration O 2 in; CO 2 out roots exchange gases within air spaces in soil Why does over-watering kill a plant?
Ascent of xylem fluid Transpiration pull generated by leaf
On a plant… What’s a source…What’s a sink? can flow 1m/hr Pressure flow in phloem Mass flow hypothesis – “source to sink” flow direction of transport in phloem is dependent on plant’s needs – phloem loading active transport of sucrose into phloem increased sucrose concentration decreases H 2 O potential – water flows in from xylem cells increase in pressure due to increase in H 2 O causes flow
Transport of sugars in phloem Loading of sucrose into phloem – flow through cells via plasmodesmata – proton pumps cotransport of sucrose into cells down proton gradient
Growth of the pollen tube and double fertilization If a pollen grain germinates, a pollen tube grows down the style toward the ovary. Stigma The pollen tube discharges two sperm into the female gametophyte (embryo sac) within an ovule. One sperm fertilizes the egg, forming the zygote. The other sperm combines with the two polar nuclei of the embryo sac’s large central cell, forming a triploid cell that develops into the nutritive tissue called endosperm. 1 2 3 Polar nuclei Egg Pollen grain Pollen tube 2 sperm Style Ovary Ovule (containing female Gametophyte, or Embryo sac) Micropyle Ovule Polar nuclei Egg Two sperm about to be discharged Endosperm nucleus (3n) (2 polar nuclei plus sperm) Zygote (2n) (egg plus sperm)
Seed structure (a) Common garden bean, a eudicot with thick cotyledons. The fleshy cotyledons store food absorbed from the endosperm before the seed germinates. (b) Castor bean, a eudicot with thin cotyledons. The narrow, membranous cotyledons (shown in edge and flat views) absorb food from the endosperm when the seed germinates. (c) Maize, a monocot. Like all monocots, maize has only one cotyledon. Maize and other grasses have a large cotyledon called a scutellum. The rudimentary shoot is sheathed in a structure called the coleoptile, and the coleorhiza covers the young root. Seed coat Radicle Epicotyl Hypocotyl Cotyledons Seed coat Endosperm Cotyledons Epicotyl Hypocotyl Radicle Scutellum (cotyledon) Coleoptile Coleorhiza Pericarp fused with seed coat Endosperm Epicotyl Hypocotyl Radicle
Ectotherms do not regulate their body temperature in any way
Most materials are transported through the blood stream of mammals and into and out of tissues by active transport.
Arranged as a Phospholipid bilayer polar hydrophilic heads nonpolar hydrophobic tails polar hydrophilic heads Serves as a cellular barrier / border H2OH2O sugar lipids salt waste impermeable to polar molecules
Proteins domains anchor molecule Within membrane – nonpolar amino acids hydrophobic anchors protein into membrane On outer surfaces of membrane in fluid – polar amino acids hydrophilic extend into extracellular fluid & into cytosol Polar areas of protein Nonpolar areas of protein
Many Functions of Membrane Proteins Outside Plasma membrane Inside Transporter Cell surface receptor Enzyme activity Cell surface identity marker Attachment to the cytoskeleton Cell adhesion “Antigen” “Channel”
Membrane Proteins Proteins determine membrane’s specific functions – cell membrane & organelle membranes each have unique collections of proteins Classes of membrane proteins: – peripheral proteins loosely bound to surface of membrane ex: cell surface identity marker (antigens) – integral proteins penetrate lipid bilayer, usually across whole membrane transmembrane protein ex: transport proteins – channels, pumps
Membrane carbohydrates Play a key role in cell-cell recognition – ability of a cell to distinguish one cell from another antigens – important in organ & tissue development – basis for rejection of foreign cells by immune system
In each of the following pairs the two terms given mean the same thing and do the same job. – leukocyte; lymphocyte – antigen; antibody – B lymphocyte; T lymphocyte – cytotoxic T cell; helper T cell
Leukocytes: Phagocytic WBCs Attracted by chemical signals released by damaged cells – ingest pathogens – digest in lysosomes Neutrophils – most abundant WBC (~70%) – ~ 3 day lifespan Macrophages – “big eater”, long-lived Natural Killer Cells – destroy virus-infected cells & cancer cells
Natural Killer Cells perforate cells – release perforin protein – insert into membrane of target cell – forms pore allowing fluid to flow in & out of cell – cell ruptures (lysis) apoptosis Destroying cells gone bad! perforin punctures cell membrane cell membrane natural killer cell cell membrane virus-infected cell vesicle perforin
Specific defense with memory – lymphocytes B cells T cells – antibodies immunoglobulins Responds to… – antigens cellular name tags – specific pathogens – specific toxins – abnormal body cells (cancer) 3rd line: Acquired (active) Immunity B cell
“self”“foreign” How are invaders recognized? Antigens – cellular name tag proteins “self” antigens – no response from WBCs “foreign” antigens – response from WBCs – pathogens: viruses, bacteria, protozoa, parasitic worms, fungi, toxins – non-pathogens: cancer cells, transplanted tissue, pollen
Lymphocytes B cells – mature in bone marrow – humoral response system attack pathogens still circulating in blood & lymph – produce antibodies T cells – mature in thymus – cellular response system attack invaded cells “Maturation” – learn to distinguish “self” from “non-self” antigens if react to “self” antigens, cells are destroyed during maturation bone marrow
Antibodies Proteins that bind to a specific antigen – multi-chain proteins – binding region matches molecular shape of antigens – each antibody is unique & specific millions of antibodies respond to millions of foreign antigens – tagging “handcuffs” “this is foreign…gotcha!” each B cell has ~50,000 antibodies Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y antigen antigen- binding site on antibody variable binding region
Vaccinations Immune system exposed to harmless version of pathogen – stimulates B cell system to produce antibodies to pathogen “active immunity” – rapid response on future exposure – creates immunity without getting disease! Most successful against viruses
Attack of the Killer T cells Killer T cell binds to infected cell Destroys infected body cells – binds to target cell – secretes perforin protein punctures cell membrane of infected cell – apoptosis infected cell destroyed cell membrane Killer T cell cell membrane target cell vesicle perforin punctures cell membrane
Blood and filtrate move in the same direction through the nephrons of the kidney and this helps conserve energy.
Osmotic control in nephron How is all this re-absorption achieved? – tight osmotic control to reduce the energy cost of excretion – use diffusion instead of active transport wherever possible the value of a counter current exchange system
Summary Not filtered out – cells u proteins – remain in blood (too big) Reabsorbed: active transport – Na + u amino acids – Cl – u glucose Reabsorbed: diffusion – Na + u Cl – –H2O–H2O Excreted – urea – excess H 2 O u excess solutes (glucose, salts) – toxins, drugs, “unknowns” why selective reabsorption & not selective filtration?
Neurons are at equilibrium at resting potential.
Nervous system cells dendrites cell body axon synaptic terminal Neuron a nerve cell Structure fits function many entry points for signal one path out transmits signal signal direction signal direction dendrite cell body axon synapse myelin sheath
Cells have voltage! Opposite charges on opposite sides of cell membrane – membrane is polarized negative inside; positive outside charge gradient stored energy (like a battery) +++++++++++++++ +++++++++++++++ –––––––––––––– ––––––––––––––
Gate +– + + channel closed channel open How does a nerve impulse travel? Wave: nerve impulse travels down neuron – change in charge opens next Na + gates down the line “voltage-gated” channels – Na + ions continue to diffuse into cell – “wave” moves down neuron = action potential ––++++++–++++++ ––++++++–++++++ ++––––––+–––––– ++––––––+–––––– Na + wave The rest of the dominoes fall!
1.Resting potential 2.Stimulus reaches threshold potential 3.Depolarization Na + channels open; K + channels closed 4.Na + channels close; K + channels open 5.Repolarization reset charge gradient 6.Undershoot K + channels close slowly Action potential graph –70 mV –60 mV –80 mV –50 mV –40 mV –30 mV –20 mV –10 mV 0 mV 10 mV Depolarization Na + flows in 20 mV 30 mV 40 mV Repolarization K + flows out Threshold Hyperpolarization (undershoot) Resting potential Resting 1 2 3 4 5 6 Membrane potential
The nervous and endocrine systems send completely different kinds of messages so they never work together.
axon terminal synaptic vesicles muscle cell (fiber) neurotransmitter acetylcholine (ACh) receptor protein Ca ++ synapse action potential Chemical synapse Events at synapse action potential depolarizes membrane opens Ca ++ channels neurotransmitter vesicles fuse with membrane release neurotransmitter to synapse diffusion neurotransmitter binds with protein receptor ion-gated channels open neurotransmitter degraded or reabsorbed We switched… from an electrical signal to a chemical signal
LE 11-4 Paracrine signaling Local regulator diffuses through extracellular fluid Secretory vesicle Secreting cell Target cell Local signaling Electrical signal along nerve cell triggers release of neurotransmitter Neurotransmitter diffuses across synapse Endocrine cell Blood vessel Long-distance signaling Hormone travels in bloodstream to target cells Synaptic signaling Target cell is stimulated Hormonal signaling Target cell
All hormones have the same types of effects on cells, no matter what they are made of.
LE 11-5_3 EXTRACELLULAR FLUID Reception Plasma membrane Transduction CYTOPLASM Receptor Signal molecule Relay molecules in a signal transduction pathway Response Activation of cellular response
LE 11-6 EXTRACELLULAR FLUID Plasma membrane The steroid hormone testosterone passes through the plasma membrane. Testosterone binds to a receptor protein in the cytoplasm, activating it. The hormone- receptor complex enters the nucleus and binds to specific genes. The bound protein stimulates the transcription of the gene into mRNA. The mRNA is translated into a specific protein. CYTOPLASM NUCLEUS DNA Hormone (testosterone) Receptor protein Hormone- receptor complex mRNA New protein
LE 11-7b Signal molecule Helix in the membrane Signal-binding site Tyr Tyrosines Receptor tyrosine kinase proteins (inactive monomers) CYTOPLASM Tyr Activated tyrosine- kinase regions (unphosphorylated dimer) Signal molecule Dimer Fully activated receptor tyrosine-kinase (phosphorylated dimer) Tyr P P P P P P ATP 6 ADP Tyr P P P P P P Inactive relay proteins Cellular response 2 Cellular response 1 Activated relay proteins 6
LE 11-10 cAMP ATP Second messenger First messenger (signal molecule such as epinephrine) G-protein-linked receptor G protein Adenylyl cyclase Protein kinase A Cellular responses GTP
LE 11-8 Signal molecule Activated relay molecule Receptor Inactive protein kinase 1 Active protein kinase 1 Inactive protein kinase 2 Active protein kinase 2 Inactive protein kinase 3 Active protein kinase 3 ADP Inactive protein Active protein Cellular response Phosphorylation cascade ATP PP P i ADP ATP PP P i ADP ATP PP P i P P P
All populations will increase continuously, regardless of outside factors.
Survivorship curves Generalized strategies What do these graphs tell about survival & strategy of a species? I.High death rate in post-reproductive years II.Constant mortality rate throughout life span III.Very high early mortality but the few survivors then live long (stay reproductive)
Reproductive strategies K-selected – late reproduction – few offspring – invest a lot in raising offspring primates coconut r-selected – early reproduction – many offspring – little parental care insects many plants K-selected r-selected
K = carrying capacity Logistic rate of growth Can populations continue to grow exponentially? Of course not! effect of natural controls no natural controls What happens as N approaches K?
Population growth predicted by the logistic model dN dt 1.0N Exponential growth Logistic growth dN dt 1.0N 1,500 N 1,500 K 1,500 0 51015 0 500 1,000 1,500 2,000 Number of generations Population size (N)