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81 Cards in this Set
- Front
- Back
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signal transduction pathway
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-sequence of molar events and chemical reactions that lead to a cellular response, following the receptor's activation by a signal.
-signal, receptor, response -may produce short or long term responses |
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autocrine
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-signals affect the same cells that release them
-only in cell |
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paracrine
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-signals diffuse to and affect nearby cells
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hormones
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-travel to distant cells
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allosteric regulation
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-common mechanism of signal transduction
-change shape in protein as a result of a molecule binding to it |
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ligands
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-not metabolized, their binding may expose at an active site on a receptor
-binding is reversible |
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inhibitor
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-aka antagonist
-can bind in place of normal ligand -closes active site |
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cell receptors classified by activity
3 receptors |
-ion receptors
-dimensional receptors -g protein-linked receptors |
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ion channel receptors
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-aka gated ion channels
-change their 3-dimensional shape when a ligand binds (acetylcholine receptor) -ie. nervous system |
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protein kinase receptors
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-change their shape when ligand bonds
-new shape exposes or activates cytoplasmic domain that has catalytic |
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g protein receptors
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-ligands binding to g protein-linked receptors expose a site that can bind to a membrane protein
-signal attaches to receptor transmembrane -changes shape and gets phosphorylated -will activate effector protein and all reactions will happen by phosphorelation |
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signal transduction
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-initiates a cascade of protein interactions-signal can amplified and distributed to cause different responses
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second messages
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-intermediary between the receptor and cascade responses
-fight of flight response, epinephrine activates the liver enzyme glycogen phosphorylase -breakdown of glycogen to provide quick energy |
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signal cascade
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-enzymes may be either activated or inhibited by other enzymes
-in liver cells, signal cascade begins when epinephrine stimulates g protein-mediated protein kinase pathway |
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signal transduction ends
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-after cell responds
-enzymes convert each transducer back to its inactive precursor -balance between regulating enzymes and signal enzymes determines cell's response |
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metabolic pathways
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-energy is stored in chemical bonds and can be released and transformed
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free energy
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-chemical energy available to do work
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5 principles governing metabolic pathways
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1. Chemical transformations occur in a series of intermediate reactions that form a metabolic pathway.
2. Each reaction is catalyzed by a specific enzyme. 3. Most metabolic pathways are similar in all organisms. 4. In eukaryotes, many metabolic pathways occur inside specific organelles. 5. Each metabolic pathway is controlled by enzymes that can be inhibited or activated. |
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exergonic reaction
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-release energy
-cell respiration -catabolism - (+) - hydrolysis of ATP - ATP + H20 -> ADP + Pi + free energy |
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endergonic reaction
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-requires energy
-active transport -cell movements -anabolism - (-) |
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redox reactions
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-can also be transferred by transfer of electrons in oxidation-reduction
-Na + Cl (becomes oxidized loses electrons)-> Na+ + Cl- (becomes reduced gains electrons) -transfers of hydrogen atoms involve transfers of electrons -when a molecule loses a hydrogen atom it becomes oxidized -more reduced a molecule is, the more energy is stored in its bonds -coenzyme NAD+ (oxidized) is key electron carrier in redox reactions. NADH (reduced form) |
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reduction
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-gain of 1 or more electons
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oxidation
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-loss of 1 or more electons
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oxidative phoshorylation
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-transfers energy from nadh to atp
-couples with of nadh: nadh ->nad+ + H+ + 2e- + energy -with production of atp: energy + adp + p1 -> ATP |
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cellular respiration
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-oxidation occurs in a series of small steps in 3 pathways: glycolysis, pyruvate oxidation, citric acid cycle
-6 sugar, needs energy (2 atp), specific enzyme, 10 reactions, 2 3-carbon pyruvate, produce 2 atp and 2 nadh |
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glycolysis
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-10 reactions
-takes place in cytososol -final product: 2 molecules of pyruvate (pyruvic acid), 2 molecules of ATP, 2 molecules of NADH -in step 5 multiply by 2 -uses 2 atp, produce 4 so net is 2 -produces 4 nadh so net is 4 |
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pyruvate oxidation
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-in inner membrane of mitochondria
-products: CO2 and acetate; acetate is then bound to CoA -draw diagram |
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citric acid cycle
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-aka krebs cycle
-in mitochondria -8 reactions, operates twice for every glucose molecule that enters glycolysis -starts with 2 acetyl CoA; acetyl group is oxidized to 2 CO2 -oxaloacetate is regenerated in last step -2 cycles that produce 3 nadh, 2 fadh, 2 atp, and 2 co2 |
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respiratory chain
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-nadh is reoxidized to nad+ and O2 is reduced to H2o
-series of redox carrier proteins embedded in inner mitochondrial membrane |
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electron transport chain
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-nadh is reoxidized to nad+ and O2 is reduced to H2o
-electrons from the oxidation of nadh and fadh2 pass from one carrier to next in the chain -32-34 atp added to glycolysis 36-38 atp produced in mitochondria |
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energetics total balance
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-from 1 glucose produce about 36-38 of atp
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fermentation
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-under anaerobic conditions, nadh is reoxidized by fermentation
-many different types, but all operate to regenerate NAD+ -overall yield of ATP is only 2- the atp made in glycoysis |
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alcoholic fermentation
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-pyruvate is converted to ethanol in 2 steps, with the first releasing of co2
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lactic acid fermentation
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-pyruvate is reduced to nadh, forming lactate as an end product, with no release of co2
-no oxygen needed |
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catabolism
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-polysaccharides are hydrolyzed to glucose, which enter glycolysis
-lipids break down to fatty acids and glycerol. fatty acids can be converted to acetyl coa -proteins are hydrolyzed to amino acids that can feed into glycolysis or citric acid cycle |
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anabolism
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-many catabolic pathways can operate in reverse
-gluconegenesis- citric acid cycle and glycolysis intermediates can be reduced to form glucose -acetyl coa can be used to form fattly acids (krebs cycle) -some citric acid intermediates can for nucleic acids |
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cell division
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-lifespan of an organism is lined to cell reproduction
-important in growth and tissue repair |
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2 basic strategies of reproducing
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-asexual
-sexual |
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cell division
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-lifespan of an organism is lined to cell reproduction
-important in growth and tissue repair |
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asexual reproduction
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-offspring are clones-genetically identical to parent
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mutation
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-any genetic variations
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binary fission
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-prokaryotes
-dna replication -2 identical daughter cells -cytokenesis |
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sexual reproduction
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-requires gametes- 2 parents each contribute 1 gamete to offspring
-gametes form by meiosis -gametes and offspring differ genetically from each other and from parents (sex cells) |
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chromosomes
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-where in dna eukaryotics is organized
-chromatin makes chromosomes |
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somatic cells
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-body cells not specialized for reproduction
-not gametes but is mitosis -each contain 2 sets of chromosomes (homologs) that occur in homologous pair -human somatic cells have 23 pairs of chromosomes |
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mitosis
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-eukaryote cells
-dna replication -stomatic cells -cytokinesis -separate single |
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meiosis
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-eukaryotes
-gametes (sperm + eggs) -results in 1 set of chromosomes in each gamete -2 nuclear divisions but dna is replicated only once -reduce the chromosome number -separate pairs -guarantees variation |
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gametes
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-contain only 1 set of chromosomes- 1 homolog from each pair
-only type of human cells produced by meiosis -reproductive cells |
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haploid cells
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-chromosomes = n
-1 set of homolog chormosomes |
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fertilization
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-2 haploid gametes (egg and sperm) fuse to form zygote
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diploid
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-chromosomes number in zygote = 2n
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essence of sexual reproduction
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-allows random selection of half diploid chromosomes in set
-this forms haploid gamete that fuses with another male diploid cell -no 2 individuals have exactly the same genetic makeup |
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cell division 4 events
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-reproductive signal- to initiate cell division
-replication of dna -segregation- distribution of dna into 2 new cells -cytokinesis- division of cytoplasm and separation of 2 new cells |
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prokaryotic cell division
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-have 1 chromosome, single molecule of dna-usually circular
-2 important regions in reproduction: -ori- where replication starts -ter- where replication ends |
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cytokinesis
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-begins after chromosome segregation by pinching in of the plasma membrane
-as membrane pinches in, new cell wall materials are synthesized resulting in separation of 2 cells |
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eukaryotic cell division
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-eukaryotic cells divide by mitosis followed by cytokinesis
-replication of dna occurs as long strands are threaded through replication complexes -dna replication only occurs during a specific stage of the cell cycle -in segregation of dna after cell division, one copy of each chromosome ends up in each of the 2 new cells -mitosis segregates chromosomes into 2 new nuclei- the cytoskeleton is involved in the process -the process in plant cells(which have cell walls) is different than in animal cell (which do not have cell )walls |
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phases of cell cycle
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-mitotic phase (mitosis and cytokinesis)
-interphase (cell growth and copying of chromosomes in preparation of cell division) about 90% of the cell cycle, subphases: -g1, s, g2 -cell growth during all 3 phases ,but chromosomes are duplicated only during s phase (synthesis) |
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5 phases of mitosis
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-prophase
-prometaphase -metaphase -anaphase -telophase |
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during interphase
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-the nuclear envelope and nucleolus are visible
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3 structures appear in prophase
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-condensed chromosomes, centrosome, spindle
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during prometaphase
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-nuclear envelop breaks down
-chromosomes consisting of 2 chromatids attach to kinetochore microtubules |
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during metaphase
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-chromosomes line up at the midline of cell
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during anaphase
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-separation of sister chromatids happens
-after separation, they move to opposite ends of spindle and are referred to as daughter chromosomes |
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telophase
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-occurs after chromosomes separate
-spindle breaks down -chromosomes uncoil -nuclear envelope and nucleoli appear -2 daughter nuclei are formed with identical genetic information -cytokinesis is well underway by late telophase |
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after cytokenesis
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-each daughter cell contains all components of complete cell
-chromosomes are precisely distributed -orientation of cell division is important to development, but organelles are not always evenly distributed |
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genes
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-units of heredity, and are made up of segments of dna
-passed to next generation through reproductive cell called gametes -dna packaged in chromosome -one set of chromosomes is inherited from each parent |
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karotype
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-ordered display of pairs of chromosomes from a cell
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homologous chromosomes
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-2 chromosomes in each pair
-same length and carry genes controlling same inherited characters |
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sex chromosomes
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- called x and y
-human females of homologous pair of x chromosomes (xx) -human males have one x and one y (xy) -each pair include one chromosome from each parent -46 chromosomes in human somatic cell are 2 sets of 23: one set from the mother and 1 from the father -diploid cell (2n) has 2 sets of chromosomes -for humans diploid number is 46 (2n = 46) |
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autosomes
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-22 pairs of chromosomes that do not determine sex
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function of meiosis
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-reduce the chromosome number from diploid to haploid
-ensure that each haploid has complete set of chromosomes -generate diversity among products |
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in meiosis I
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-reduces chromosome number
-homologous pairs of chromosomes come together and line up along their entire lengths |
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after metaphase I
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-homologous chromosome pairs separate, but individual chromosomes made up of 2 sister chromatids remain together
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during meiosis II
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-sister chromatids separate, which is not proceeded by dna replication
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products of meiosis 1 & 2
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- 4 cells with a haploid number of chromosomes
-these 4 cells are not genetically identical -2 processes may occur: crossing over and independent assortment |
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crossing over
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-in meiosis
-an exchange of genetic material that occurs at chiasma -results in recombinant chromatids and increase genetic variability of products |
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in mieosis prophase I
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-may last a long time
-in human males: prophase I lasts about 1 week, and 1 month for entire meitoic cycle -in human females: prophase l begins before birth, and ends up to decades later during monthly ovarian cycle |
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independent assortment
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-during anaphase I allows for chance combinations and genetic diversity
-after homologous chromosomes line up at metaphase I, it is a matter of chance which member of a pair goes to which daughter cell -the more chromosomes involved , the more combinations possible |
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nondisjunction
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-meiotic errors
-homologous pair fail to separate at anaphase I- sister chromatids fail to separate, or homologus chromosomes may not remain together -either results in aneuoloidy- chromosomes lacking or present in excess |
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polyploidy
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-nondisjuction
-organisms with triploid (3n), tetraploid (4n), and even higher levels called polyploid -this can occur through an extra round of dna duplication before meiosis II -occurs naturally in some species, and can be desirable in plants |
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breaking of chormosomes can lead to four types of changes in chromosome structure
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-deletion removes chromosomal segment
-duplication repeats segment -inversion reverses segment within chromosome -translocation moves segment from 1 chromosome to another |
