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Enzymes are necessary because they cause reactions to happen.

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Presentation on theme: "Enzymes are necessary because they cause reactions to happen."— Presentation transcript:

1 Enzymes are necessary because they cause reactions to happen.

2 Metabolism Chemical reactions of life forming bonds between molecules
dehydration synthesis synthesis anabolic reactions breaking bonds between molecules hydrolysis digestion catabolic reactions That’s why they’re called anabolic steroids!

3 Examples dehydration synthesis (synthesis) hydrolysis (digestion)
enzyme hydrolysis (digestion) enzyme

4 Enzymes work by decreasing the potential energy difference between reactant and product

5 Catalysts So what’s a cell got to do to reduce activation energy?
get help! … chemical help… ENZYMES Call in the ENZYMES! G

6 As a result of its involvement in a reaction, an enzyme permanently alters its shape.

7 Enzymes vocabulary substrate product active site active site products
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 active site products substrate enzyme

8 Properties of enzymes Reaction specific Not consumed in reaction
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

9 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.

10 Managing water balance
Cell survival depends on balancing water uptake & loss freshwater balanced saltwater

11 Aquaporins 1991 | 2003 Water moves rapidly into & out of cells
evidence that there were water channels protein channels allowing flow of water across cell membrane Peter Agre John Hopkins Roderick MacKinnon Rockefeller

12 Do you understand Osmosis…
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

13 Cellular respiration is only done by heterotrophs because autotrophs can make their own energy.

14 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 CO2 H2O N P K


16 The purpose of fermentation is to produce a small amount of energy when cells don’t have access to oxygen.

17 Alcohol Fermentation pyruvate  ethanol + CO2 Dead end process
bacteria yeast recycle NADH 1C 3C 2C pyruvate  ethanol + CO2 NADH NAD+ back to glycolysis Dead end process at ~12% ethanol, kills yeast can’t reverse the reaction Count the carbons!

18 Lactic Acid Fermentation
animals some fungi recycle NADH O2 pyruvate  lactic acid 3C NADH NAD+ back to glycolysis Reversible process once O2 is available, lactate is converted back to pyruvate by the liver Count the carbons!

19 Plants use water only as a means of keeping their cells full and holding the plant itself upright.

20 ETC of Photosynthesis Chloroplasts transform light energy into chemical energy of ATP use electron carrier NADPH Two places where light comes in. Remember photosynthesis is endergonic -- the electron transport chain is driven by light energy. Need to look at that in more detail on next slide generates O2

21 The second step of photosynthesis is called the dark reactions because it only happens in the dark.

22 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?

23 From Light reactions to Calvin cycle
chloroplast stroma Need products of light reactions to drive synthesis reactions ATP NADPH stroma ATP thylakoid

24 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)



27 One trait = one gene


29 All proteins are made of enzymes.

30 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) Storage: beans (seed proteins) Movement: muscle fibers Cell surface proteins: labels that ID cell as self vs. foreign Antibodies: recognize the labels ENZYMES!!!!

31 Structural homologies only exist in animals, never in plants.


33 When the environment changes all species living in it will change to adapt to it.




37 Whales lost their hind limbs because they stopped using them.

38 Homologous structures
Similar structure Similar development Different functions Evidence of close evolutionary relationship recent common ancestor


40 Analogous structures Separate evolution of structures
similar functions similar external form different internal structure & development different origin no evolutionary relationship Don’t be fooled by their looks! Solving a similar problem with a similar solution

41 Convergent evolution Flight evolved in 3 separate animal groups
analogous structures Does this mean they have a recent common ancestor?

42 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!

43 Bird and bat wings can only be described as homologous structures, not as analogous structures.


45 The strongest evidence supporting the endosymbiotic theory is that mitochondria and bacteria are the same size and have a similar shape.


47 The primitive atmosphere had to contain oxygen before life could evolve.

48 Plants are simple organisms with no tissues or organs.

49 Plant TISSUES Dermal Ground Vascular epidermis (“skin” of plant)
single layer of tightly packed cells that covers & protects plant Ground bulk of plant tissue photosynthetic mesophyll, storage Vascular transport system in shoots & roots xylem & phloem

50 Basic plant anatomy 3 root shoot (stem) leaves root tip root hairs
nodes internodes buds terminal or apical buds axillary buds flower buds & flowers leaves mesophyll tissue veins (vascular bundles)

51 Plants actively move water up their trunks.

52 Transport in plants H2O & minerals transport in xylem Transpiration
Adhesion, cohesion & Evaporation Sugars transport in phloem bulk flow Gas exchange photosynthesis CO2 in; O2 out stomates respiration O2 in; CO2 out roots exchange gases within air spaces in soil Why does over-watering kill a plant?

53 Ascent of xylem fluid Transpiration pull generated by leaf

54 Plants get food from the ground.

55 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 H2O potential water flows in from xylem cells increase in pressure due to increase in H2O causes flow can flow 1m/hr In contrast to the unidirectional transport of xylem sap from roots to leaves, the direction that phloem sap travels is variable. However, sieve tubes always carry sugars from a sugar source to a sugar sink. A sugar source is a plant organ that is a net producer of sugar, by photosynthesis or by breakdown of starch. Mature leaves are the primary sugar sources. A sugar sink is an organ that is a net consumer or storer of sugar. Growing roots, buds, stems, and fruits are sugar sinks. A storage organ, such as a tuber or a bulb, may be a source or a sink, depending on the season. When stockpiling carbohydrates in the summer, it is a sugar sink. After breaking dormancy in the spring, it is a source as its starch is broken down to sugar, which is carried to the growing tips of the plant. A sugar sink usually receives sugar from the nearest sources. Upper leaves on a branch may send sugar to the growing shoot tip, whereas lower leaves export sugar to roots. A growing fruit may monopolize sugar sources around it. For each sieve tube, the direction of transport depends on the locations of the source and sink connected by that tube. Therefore, neighboring tubes may carry sap in opposite directions. Direction of flow may also vary by season or developmental stage of the plant. On a plant… What’s a source…What’s a sink?

56 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

57 Plants do not do sexual reproduction.

58 The life cycle of an angiosperm
Nucleus of developing endosperm (3n) Zygote (2n) FERTILIZATION Embryo (2n) Endosperm (food supply) (3n) Seed coat (2n) Seed Germinating seed Pollen tube Sperm Stigma grains Style Discharged sperm nuclei (n) Egg nucleus (n) Mature flower on sporophyte plant (2n) Key Haploid (n) Diploid (2n) Anther Ovule with megasporangium (2n) Male gametophyte (in pollen grain) Microspore (n) MEIOSIS Microsporangium Microsporocytes (2n) Generative cell Tube cell Surviving megaspore (n) Ovary Megasporangium Female gametophyte (embryo sac) Antipodal cells Polar nuclei Synergids Egg (n)

59 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 Two sperm about to be discharged Endosperm nucleus (3n) (2 polar nuclei plus sperm) Zygote (2n) (egg plus sperm)

60 Seed structure Seed coat Epicotyl Hypocotyl Radicle Cotyledons
(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 Endosperm Scutellum (cotyledon) Coleoptile Coleorhiza Pericarp fused with seed coat

61 Ectotherms do not regulate their body temperature in any way


63 Most materials are transported through the blood stream of mammals and into and out of tissues by active transport.

64 Arranged as a Phospholipid bilayer
Serves as a cellular barrier / border sugar H2O salt polar hydrophilic heads nonpolar hydrophobic tails impermeable to polar molecules polar hydrophilic heads waste lipids

65 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

66 Many Functions of Membrane Proteins
“Channel” Outside Plasma membrane Inside Transporter Enzyme activity Cell surface receptor “Antigen” Signal transduction - transmitting a signal from outside the cell to the cell nucleus, like receiving a hormone which triggers a receptor on the inside of the cell that then signals to the nucleus that a protein must be made. Cell surface identity marker Cell adhesion Attachment to the cytoskeleton

67 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

68 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 The four human blood groups (A, B, AB, and O) differ in the external carbohydrates on red blood cells.

69 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

70 1st line: Non-specific External defense
Barrier skin Traps mucous membranes, cilia, hair, earwax Elimination coughing, sneezing, urination, diarrhea Unfavorable pH stomach acid, sweat, saliva, urine Lysozyme enzyme digests bacterial cell walls tears, sweat Lining of trachea: ciliated cells & mucus secreting cells

71 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

72 Destroying cells gone bad!
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 vesicle natural killer cell perforin cell membrane perforin punctures cell membrane cell membrane virus-infected cell

73 3rd line: Acquired (active) Immunity
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) B cell

74 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 “self” “foreign”

75 Lymphocytes B cells T 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 Tens of millions of different T cells are produced, each one specializing in the recognition of oen particar antigen.

76 Antibodies Proteins that bind to a specific antigen
Y Y Y Y Y Y Y Y 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!” Y Y Y Y Y Y antigen- binding site on antibody antigen Y Y Y variable binding region Y Y each B cell has ~50,000 antibodies

77 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

78 Attack of the Killer T cells
Destroys infected body cells binds to target cell secretes perforin protein punctures cell membrane of infected cell apoptosis vesicle Killer T cell Killer T cell binds to infected cell cell membrane perforin punctures cell membrane cell membrane infected cell destroyed target cell

79 Blood and filtrate move in the same direction through the nephrons of the kidney and this helps conserve energy.

80 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 Descending limb of the loop of Henle. Reabsorption of water continues as the filtrate moves into the descending limb of the loop of Henle. This transport epithelium is freely permeable to water but not very permeable to salt and other small solutes. For water to move out of the tubule by osmosis, the interstitial fluid bathing the tubule must be hyperosmotic to the filtrate. Because the osmolarity of the interstitial fluid does become progressively greater from the outer cortex to the inner medulla, the filtrate moving within the descending loop of Henle continues to loose water. Ascending limb of the loop of Henle. In contrast to the descending limb, the transport epithelium of the ascending limb is permeable to salt, not water. As filtrate ascends the thin segment of the ascending limb, NaCl diffuses out of the permeable tubule into the interstitial fluid, increasing the osmolarity of the medulla. The active transport of salt from the filtrate into the interstitial fluid continues in the thick segment of the ascending limb. By losing salt without giving up water, the filtrate becomes progressively more dilute as it moves up to the cortex in the ascending limb of the loop. the value of a counter current exchange system

81 why selective reabsorption & not selective filtration?
Summary why selective reabsorption & not selective filtration? 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 Excreted urea excess H2O u excess solutes (glucose, salts) toxins, drugs, “unknowns”

82 Neurons are at equilibrium at resting potential.

83 Nervous system cells Neuron a nerve cell Structure fits function
signal direction dendrites cell body Structure fits function many entry points for signal one path out transmits signal axon signal direction synaptic terminal myelin sheath dendrite  cell body  axon synapse

84 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) + This is an imbalanced condition. The positively + charged ions repel each other as do the negatively - charged ions. They “want” to flow down their electrical gradient and mix together evenly. This means that there is energy stored here, like a dammed up river. Voltage is a measurement of stored electrical energy. Like “Danger High Voltage” = lots of energy (lethal). +

85 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 Gate + channel closed channel open The rest of the dominoes fall! + Na+ wave 

86 Action potential graph
Resting potential Stimulus reaches threshold potential Depolarization Na+ channels open; K+ channels closed Na+ channels close; K+ channels open Repolarization reset charge gradient Undershoot K+ channels close slowly 40 mV 4 30 mV 20 mV Depolarization Na+ flows in Repolarization K+ flows out 10 mV 0 mV –10 mV 3 5 Membrane potential –20 mV –30 mV –40 mV Hyperpolarization (undershoot) –50 mV Threshold –60 mV 2 –70 mV 1 Resting potential 6 Resting –80 mV

87 The nervous and endocrine systems send completely different kinds of messages so they never work together.

88 Chemical synapse Events at synapse ion-gated channels open
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 axon terminal action potential synaptic vesicles synapse Ca++ Calcium is a very important ion throughout your body. It will come up again and again involved in many processes. neurotransmitter acetylcholine (ACh) receptor protein muscle cell (fiber) We switched… from an electrical signal to a chemical signal

89 LE 11-4 Local signaling Long-distance signaling Target cell
Electrical signal along nerve cell triggers release of neurotransmitter Endocrine cell Blood vessel Neurotransmitter diffuses across synapse Secreting cell Secretory vesicle Hormone travels in bloodstream to target cells Local regulator diffuses through extracellular fluid Target cell is stimulated Target cell Paracrine signaling Synaptic signaling Hormonal signaling

90 All hormones have the same types of effects on cells, no matter what they are made of.

91 Relay molecules in a signal transduction
EXTRACELLULAR FLUID CYTOPLASM Plasma membrane Reception Transduction Response Receptor Activation of cellular response Relay molecules in a signal transduction pathway Signal molecule

92 LE 11-6 Hormone EXTRACELLULAR (testosterone) FLUID The steroid
hormone testosterone passes through the plasma membrane. Plasma membrane Testosterone binds to a receptor protein in the cytoplasm, activating it. Receptor protein Hormone- receptor complex The hormone- receptor complex enters the nucleus and binds to specific genes. DNA mRNA The bound protein stimulates the transcription of the gene into mRNA. NUCLEUS New protein The mRNA is translated into a specific protein. CYTOPLASM

93 LE 11-7b Signal molecule Signal-binding site a Helix in the membrane
Tyrosines Tyr Tyr Tyr Tyr Tyr Tyr Tyr Tyr Tyr Tyr Tyr Tyr Tyr Tyr Tyr Tyr Tyr Tyr Receptor tyrosine kinase proteins (inactive monomers) Dimer CYTOPLASM Activated relay proteins Cellular response 1 Tyr Tyr P Tyr P Tyr P Tyr Tyr P Tyr Tyr P Tyr Tyr P P P Tyr Tyr Tyr Tyr P Tyr Tyr P P Tyr Tyr P Cellular response 2 6 ATP 6 ADP Activated tyrosine- kinase regions (unphosphorylated dimer) Fully activated receptor tyrosine-kinase (phosphorylated dimer) Inactive relay proteins

94 LE 11-10 First messenger (signal molecule such as epinephrine) Adenylyl cyclase G protein G-protein-linked receptor GTP ATP Second messenger cAMP Protein kinase A Cellular responses

95 LE 11-8 Signal molecule Receptor Activated relay molecule Inactive
protein kinase 1 Active protein kinase 1 Inactive protein kinase 2 ATP ADP Active protein kinase 2 P Phosphorylation cascade PP P i Inactive protein kinase 3 ATP ADP Active protein kinase 3 P PP P i Inactive protein ATP ADP P Active protein Cellular response PP P i

96 All populations will increase continuously, regardless of outside factors.

97 Survivorship curves Generalized strategies
What do these graphs tell about survival & strategy of a species? Generalized strategies 25 1000 100 Human (type I) Hydra (type II) Oyster (type III) 10 1 50 Percent of maximum life span 75 Survival per thousand I. High death rate in post-reproductive years II. Constant mortality rate throughout life span A Type I curve is flat at the start, reflecting low death rates during early and middle life, then drops steeply as death rates increase among older age groups. Humans and many other large mammals that produce few offspring but provide them with good care often exhibit this kind of curve. In contrast, a Type III curve drops sharply at the start, reflecting very high death rates for the young, but then flattens out as death rates decline for those few individuals that have survived to a certain critical age. This type of curve is usually associated with organisms that produce very large numbers of offspring but provide little or no care, such as long–lived plants, many fishes, and marine invertebrates. An oyster, for example, may release millions of eggs, but most offspring die as larvae from predation or other causes. Those few that survive long enough to attach to a suitable substrate and begin growing a hard shell will probably survive for a relatively long time. Type II curves are intermediate, with a constant death rate over the organism’s life span. This kind of survivorship occurs in Belding’s ground squirrels and some other rodents, various invertebrates, some lizards, and some annual plants. III. Very high early mortality but the few survivors then live long (stay reproductive)

98 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

99 Logistic rate of growth
Can populations continue to grow exponentially? Of course not! no natural controls K = carrying capacity Decrease rate of growth as N reaches K effect of natural controls What happens as N approaches K?

100 Population growth predicted by the logistic model
dN dt 1.0N Exponential growth Logistic growth 1,500  N 1,500 K  1,500 5 10 15 500 1,000 2,000 Number of generations Population size (N)

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