Bio 101 test 3 power points49 cards

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1

Energy in Living Systems

-Metabolism is the sum of all chemical reactions in the body. -Metabolism transfers energy and follows the laws of thermodynamics.

2

Laws of Thermodynamics

-1st Law: Energy cannot be either created or destroyed -2nd Law: When reactions occur, they become more disordered

3

The Carbon Cycle and Energy

-Living organisms all require energy to survive -Sun is source of most energy on Earth -Light energy is used by producers to synthesize sugars --Plants performing photosynthesis

4

The Carbon Cycle and Energy

-For non-photosynthesizing organisms (mostly consumers), energy is acquired from food molecules. -Carbon dioxide and food molecules are involved in this energy transfer.

5

Using Energy from Food

-Energy transfer in nonliving systems can be explosive: --Carbon in wood + O2 > CO2 + H2O + energy -Energy transfer in cells must be controlled: --Carbon in food + O2 > CO2 + H2O + energy

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Transfer of Electrons

-Capturing energy requires transfer of electrons -Reactions that transfer electrons are called redox (oxidation/reduction) reactions --Oxidation—loss of electrons --Reduction—gain of electrons

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Metabolism

-All chemical reactions within living cells Anabolic --Biosynthetic: create complex molecules out of smaller compounds -Catabolic --Break down complex molecules to release energy

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Chemical reactions and thermodynamics

-A + B > C + D --Reactants: A + B --Products: C + D -Some chemical reactions need a “jump start” to proceed -Activation energy: --Energy needed to jump‑start a reaction

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Enzymes Speed Up Reactions

-Enzymes are biological catalysts --Lower the energy of activation --Increase the speed of reaction

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The Structure of Enzymes

-Very specific for reactions -Three‑dimensional shape determines function -Active site is region where the substrate binds --Induced fit: active site molds around substrate

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Enzymes in Metabolism

-Metabolic pathways in the body usually involve several reactions. -There may be several intermediates. -Each intermediate has its own enzyme.

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Enzyme Function

-Enzymes depend on random collisions. -Multiple enzymes may be located close together. -This maximizes molecular collisions.

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Metabolism and Life Span

-Slowing down metabolism increases life span -Higher metabolism results in toxic by products (free radicals) -Antioxidants help break down free radicals -Some examples of antioxidants --Vitamin E --Vitamin C --Beta-carotene

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Energy Carrier Molecules

-Receiving, storing, and delivering energy -Universal in all cells -ATP stores energy in phosphate bonds --Releases energy when loses a phosphate ---ATP > ADP > AMP -NADPH and NADH: high‑energy molecules --NADP+ + 2 e- and H+ > NADPH --NAD+

15

Photosynthesis and Cellular Respiration

An exchange of molecules and energy

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Structure of the Chloroplast

-Double membrane—intermembrane space -Stroma -Thylakoid disks—Thylakoid space

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Two Reactions of Photosynthesis

-Light reactions capture light energy --Take place in thylakoids --Use chlorophyll --Convert solar energy into chemical energy -Calvin Cycle --Occur in the stroma --Use the energy produced in the light reactions --Synthesize sugar from CO2 and

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Light Reactions

-Chlorophyll antennae --Capture energy from light --Pass energy to reaction centers

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Photosystem II

-Splitting of H2O --Electrons, O2,and H+ -Energized electrons --enter electron transport chain (ETC) -Energy from electron transport used to pump H+ across thylkoid membrane -Generates proton gradient

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ATP Synthase

-H+ gradient represents stored energy -Used by ATP synthase -H+ movement through ATP synthase drives phosphorylation --ADP > ATP

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Photosystem I

-Electrons passed to photosystem I -Light recharges electrons --Electrons enter ETC -NADPH is produced from: --Electrons from ETC --Hydrogen ions from stroma

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Calvin Cycle: Carbon Fixation

-Rubisco catalyzes CO2 fixation to ribulose -Begins the carbon fixation cycle

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Calvin Cycle: Carbon Fixation

-Three turns of cycle produce a 3C sugar --Glyceraldehyde 3-phosphate -Fate of glyceraldehyde 3-phosphate --Most used in mitochondria to produce ATP --Produce glucose for storage ---Sucrose and starch

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Catabolic Reactions

-Breaking down molecules for energy -Cellular respiration—three steps --Glycolysis ---Breaking down glucose --Krebs cycle ---Formation of energy carriers --Oxidative phosphorylation ---Use oxygen to produce ATP

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Fermentation

-Anaerobic Respiration --Energy production in the absence of O2 -In yeast and bacteria: --CO2 and ethyl alcohol produced -In animals: --Lactic acid produced

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The Krebs Cycle (Citric Acid Cycle)

-Pyruvate converted to acetyl CoA --Releasing CO2 -Acetyl CoA enters the cycle -Enzyme-driven steps resulting in: --2 CO2, 3 NADH,1 ATP

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Oxidative Phosphorylation

-Electrons passed from NADH to electron transport chain -H+ gradient produced --Drives ATP synthase --Phosphorylation of ADP to make ATP -O2 accepts electrons, producing water

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The Need for Cell Division

-Renewal and repair of tissues --Stem cells ---capable of self-renewal ---give rise to descendant cells -Asexual and sexual reproduction --Prokaryotes divide through binary fission --Eukaryote cell division is more complicated

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Cell cycle: Two Main Stages

-Cell cycle --Series of events in life cycle of a cell --Time to complete cell cycle ---Dependent on organism, type of cell, life stage --Two main stages ---Interphase ----Most cells spend 90% of lifespan in this stage ---Cell division --Mito

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Interphase: The Longest Stage

-The period between divisions --Longest phase of the cell cycle --The cell prepares to divide -Divided into 3 stages: --G1: growth after mitosis --S: synthesis of DNA --G2: growth before mitosis

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G1 and G2 phases

-G stands for “gap” --Early biologists saw a gap ---Between S phase and cell division --Important for two reasons periods of growth ---size of cell and protein content increase ---preparation for next phase checkpoint that ensures conditions a

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G0 Phase

Most cells are not actively dividing -These cells are in G0 phase --Can last days to years --Some cells will divide again; e.g. liver cells --Some cells stay in G0; e.g. nerve cells

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DNA Packaged as Chromosome

-DNA molecules are enormously long --Double helix nearly 2 meters in length -DNA is tightly packaged with proteins Chromatin --DNA and proteins -Chromosome --Tightly packed

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Karyotype

-Chromosomes are visible during mitosis -Their number and shape can be studied -Humans have 46 chromosomes

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Homologous Chromosomes

-46 chromosomes are arranged in 23 pairs --One came from each parent -22 pairs are autosomes --Both chromosomes are homologues -1 pair are sex chromosomes --Can be homologous; XX for females --Can be different; XY for males

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Mitosis

-Consists of five phases --Prophase --Prometaphase --Metaphase --Anaphase --Telophase -Cytokinesis: division of the cytoplasm

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Prophase

-Cell enters mitosis --Chromosomes condense --Centrosomes move apart -Go to the poles of the cell -Mitotic spindle begins to form

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Prometaphase

-Mitosis proceeds --Chromosome condensation completed --Nuclear envelope breaks down --Mitotic spindle extends from centrosomes ---Attaches to centromeres of chromosomes ---Kinetochore: site of attachment ---Chromatids linked to opposite poles

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Metaphase

-Chromosomes line up --Metaphase plate --Align sister chromatids ---Equal and balanced ---segregation

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Anaphase

-Chromatids separate --Break free and dragged to opposite sides --Microtubules shorten -Result: --Equal segregation of chromosomes in two daughter cells

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Telophase and Cytokinesis

-Telophase: --Chromosomes reach the poles --Mitotic spindle falls apart Chromosomes unfold Nuclear membrane reforms -Cytokinesis Cytoplasm is divided Two cells are formed

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Meiosis

-Used to make gametes --Eggs and sperm -Chromosome number is halved (haploid) -Zygote is diploid after fertilization

43

Genetics

-Gregor Mendel is considered the father of genetics -Published his work in 1866

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Essential Terms in Genetics

-Phenotype --Expression of a genetic trait Diploid -Two copies of each chromosome --Homologous pair ---Paternal homologue ---Maternal homologue -Haploid --Reproductive cells have only one copy of each chromosome

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Alleles

-Different versions of a given gene -Human blood groups --A,B, AB, and O --Three alleles of one gene --Alleles ---IA: A type sugar ---IB: B type sugar ---i: neither A or B

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Alleles in an Individual

-Homozygote—same two alleles (AA or aa) -Heterozygote—two different alleles (Aa) -Genotype—the genetic makeup -Phenotype—observable characteristics

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Genetic Cross

-When two individuals are mated -P generation—parent generation -F1 generation—first generation -F2 generation—second generation

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Gene Mutations

Different alleles originally arose from a mutation Mutation: -Change in DNA that makes up a gene -Mutations can be --Harmful --Beneficial --Neutral

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Basic Patterns of Inheritance

-Mendel started with true‑breeding plants -Recessive trait skipped a generation