Midterm 2 Flashcards
What is exocytosis?
It is used to export large molecules (proteins, polysaccharides), across lipid bilayers between endomembrane and outside of the cell.
What is endocytosis?
Used for importing large molecules/particles across cell membranes
What is phagocytosis?
Food particle engulfed within a vacuole
What is pinocytosis?
Very small channels in cell surface lead to small vacuoles engulfing extracellular fluid-“cell drinking.”
What is potential energy?
The energy stored within a structure
What is chemical energy?
Energy available for release in chemical reactions (bonds between atoms and molecules)
What are the 1st and 2nd laws of thermodynamics?
1st: Energy can neither be created nor destroyed; can be converted from one form to another
2nd: Disorder increases with every energy conversion, and less energy is available for work (lost as heat). Living things constantly decrease their internal disorder at the expense of their environment
What are exergonic reactions?
Reactants store more energy in their bonds than do products-difference is released during reaction.
What are endergonic reactions?
Product(s) store more potential energy within their bonds than was present within the bonds of reactions. (synthesis of molecules)
What is the energy of activation?
Bonds within molecules require initial input of energy in their breaking. It is high for many biological reactions Catalysts encourage reactions between other molecules without being a product of reaction.
What is an enzyme?
Protein with precisely shaped active site which will accommodate substrates but no other molecule(s). Shape of the active site is highly dependent upon temp and pH. Speeds up chemical reactions.
What is competitive inhibition?
A molecule that sits on active site and blocks it.
What is non-competitive inhibition?
Molecule which binds with an enzyme and changes the shape of the active site.
Cell Energetics
Cells metabolism is sum of all exergonic and endergonic reactions taking place within it. Energy coupling permits energy yielded by exergonic reactions to drive endergonic.
What is ATP?
Energy currency of solely cells. ATP can turn into ADP using hydrolysis.
Quantum of Energy
All energy stored in ATP molecule is released when the high energy phosphate bond is broken-used for work or wasted as heat. Average human produces and uses 60kg of ATP every 24 hours.
Where do the steps of aerobic respiration occur?
Glycolisis (does not require oxygen); takes place in cytoplasm
Citric Acid Cycle: Takes place in matrix of mitochondria
Electron Transport and Chemiosmosis: Wall of mitochondria, christae
What is glycolisis?
Anaerobic process, cells can still produce ATP without oxygen. 2ATP created per glucose, also yields one reduced NADH, electrons are carried to electron transport chain. Breaks glucose into 2 3C pyruvates.
What is the citric acid cycle?
Pyruvate enters this cycle, series of redox reactions that yield 1ATP, 3NADH, 1FADH2 and 3H+, 2CO2. Lots of potential energy for electron transport chain.
What is the electron transport chain?
Proteins embedded in cristae, formed from lipid bilayer. Initial protein accepts high energy electrons from NADH and FADH2. Used to pump H+ through membrane, at the end of the chain, O- picks up 2e-, 2H+ and yields 1H2O.
What is chemiosmosis?
H+ concentration between mitochondrial membranes rises above H+ concentration in the matrix. Crista membrane impermeable to H+. H+ diffuses back into matrix through ATP synthase. Every 3H+ yields sufficient energy to attach one high energy phosphate to an ADP- 1ATP generated.
What is the difference between aerobic and anaerobic respiration?
Aerobic: 36 ATP yielded per glucose molecule, 40% of potential energy
Anaerobic: 2 ATP per glucose molecule, 5% of potential energy
What is fermentation?
Used when there is no oxygen, CO2 and ethanol are the final products of alcohol fermentation (yeast and bacteria).
What is the difference between sexual and asexual reproduction?
Sexual: There is variation, as meiosis shuffles the genome, permits rapid population change
Asexual: New individual is genetically identical to parent, solely uses mitosis. Allows rapid population growth, no variation. (prokaryotes)
Why is the cell cycle important?
Because multicellular organisms require cell division for growth, repair, differentiation, and reproduction
What are the phases of interphase?
G1- Mainly growth
S-Continued growth and DNA replication
G2- Continued growth and prep for cell division
What are the phases of mitosis?
Prophase, metaphase, anaphase, telophase and cytokinesis
Prophase
Nuclear chromosomes condense and become visible
Metaphase
Nuclear envelope disappears, sister chromatids attach to spindle fibres and move towards central plane.
Anaphase
Sister chromatids aligned, planes split at centromeres and begin moving towards opposite poles of cells
Telophase
Begins after the arrival of all chromosomes at opposite poles of the parent cells, nuclear membrane is reestablished, chromosomes disperse from condensed form.
Cytokinesis
Cleavage furrow (animals), pinches parent cell in two. Plants-formation of new cell walls between daughter cells.
What are growth factors?
Binding of growth factors sets off transduction and signal changes from across membrane. Can turn genes on and off, and controls the cell cycle (intrinsic and extrinsic)
Meiosis: Prophase 1
Chromosomes condense, then homologues pair up (maternal with paternal) in synapsis to form tetrads. Crossing over occurs to mix up genes
Metaphase 1
Tetrads align upon midline, random assignment of maternal or paternal on either side-important for random selection of parent traits
Anaphase 1
Homologous chromosomes of each tetrad separate, sister chromatids still exist.
Telophase 1 and cytokinesis
Two haploid cells form (n=23)
Meoisis 2
Essentially a repeat of meiosis 1, but in anaphase 2 the centromeres separate and sister chromatids split, and 2 haploid daughter cells are formed which makes 4 total haploid cells.
What is a gene?
A spot on a chromosome. Length of DNA coding for particular protein, is always found on same location.
What is an allele?
A version of a gene, variant of the base sequence. Produces a different version of the SAME protein. Without alleles, there would be no variation.
What is crossing over and recombinant chromosomes?
Crossing over: Swapping sections of maternal and paternal DNA, which creates recombinant chromosomes and generates genetic variation. 1-3 crossover events per tetrad occur in humans.
What is a karyotype?
Number and morphology of chromosomes specific to a species. 22 autosomal chromosomes and 1 pair of sex chromosomes.
What is a non-disjunction?
Failure in separation between homologous pairs in metaphase 1 or 2. If it occurs in metaphase 1, 2 haploid cells will have 24 chromosomes, and 2 will have 22. IF it occurs in metaphase 2, haploid cells will have 24, 22, and 23 and 23 chromosomes.
What is a chromosome rearrangement?
A breakage in chromsomes
Deletion
Section is lost
Duplication
Section lost from one homologue and inserted into sister homologue.
Inversion
Section lost, rotated, and reinserted
Translocation
Fragment lost from breakage of one chromosome, attaches to another chromosome.
What are genes responsible for?
Physical characteristics and behaviours, responsible for one character of phenotype
Genotype vs Phenotype
Genotype: Total complement of genes or alleles borne by an individual organism. Also refers to specific genes.
Phenotype: Physical appearance of organism
Character
Discrete, identifiable physical feature or behaviour of an organism.
Gregor Mendel
Austrian monk, had a background in quantitative sciences. Created Mendel’s laws in 1866, which were basic principles of genetics.
What is true-breeding?
Meant to eliminate variation, produce offspring displaying only 1 trait for a particular character.
What are the advantages of breeding pea plants?
Self-fertilizing, short genetic time, don’t require lots of room to grow, lots of offspring, lots of variability, strains breed true, easy to manipulate, no intermediate traits, independent assortment, not sex linked
What is a hybrid?
Offspring of a cross between two true-breeding lines.
What was Mendel’s hypothesis?
There are genes-inheritance is particulate, there is correspondence between genes and characters. An organism will carry 2 copies of each gene, 1 version of a gene can mask another.
Hypothesis 1
Alleles of a gene produce different traits; variation in genes can produce variation in characters
Hypothesis 2
1 copy from each parent
Hypothesis 3
Alleles are dominant and recessive
Hypothesis 4
Law of Segregation: Any gamete carries only one copy of any gene
What is independent assortment?
Each pair of alleles segregates during gamete formation separate from each other.
Multiple Alleles
Any individual can have at most 2 alleles. Example: blood typing
Pleiotropy
Genes that can affect more than one phenotype-small direct effects can have large knock on effects. Example: sickle cell anaemia
Sickle Cell Anaemia
Point mutation, codes for primary structure of haemoglobin, 1 amino acid replaced. Results in red blood cells distorting into sickle shape. Physiological and morphological characteristics of sickle cell anaemia arise from blood vessel blockage, sickle cell allele does not directly cause it (pleiotropy).
Polygenic Characteristics
Single character that is controlled by multiple alleles. Ex: 3 genes control skin color, each with 2 codominant alleles, produces smooth normal distribution of possible skin colours.
Chromosome Theory of Inheritance
Genes occupy specific places (loci) upon specific chromosomes.
Linked Genes
Genes are always found in the same place on the same chromosome within a species, all genes on a chromosome are linked. Tend strongly to be inherited as a unit (3:1 phenotypic ratio).
What is the difference between molecular biology and biochemistry?
Molecular Biology: Study of DNA, its properties and roles within a cell at a molecular level
Biochemistry: Study of everything else within a cell at molecular level
How is the sugar phosphate backbone read?
Read from 3’ (sugar) end to 5’ (phosphate) end.
What are the 2 single ring pyrimidines and 2 double ring purines?
Pyrimidines- Cytosine and Thymine
Purines- Guanine and Adenine
How is DNA replicated?
Semi-conservatively, half of the DNA is kept. Enzymes lock and separate strands at the origin of replication sites.
What is the function of DNA polymerase?
Enzyme which forms new chain of nucleotides against template, adding monomers at 3’ end
Central Dogma
Genotype (DNA) encodes instructions for the primary structures of proteins.
RNA function
Transmits gene information to protein synthesis mechanism. Proteins produce phenotype.
What is a mutation and the 3 types?
Any change in the nucleotide sequence of a gene.
Substitution- one nucleotide replaces another
Deletions and Insertions- sequence of polypeptide changed from that point onwards
What switch produces sickle cell anaemia?
Replacement of glutamine with valine
What are the three types of RNA?
mRNA- transcribed from DNA, carries codons for linear sequence of amino acids
rRNA- makes up bulk of ribosome
tRNA- attaches to ribosome, carries anticodon.
What is the process of transcription in prokaryotes?
RNA polymerase attaches to promoter on “unzipped” sequencec of DNA, RNA monomers line up against corresponding DNA monomers held by hydrogen bonds. RNA polymerase joins RNA monomers into polynucleotide mRNA. mRNA then elongates and peels away, after hitting the terminator.
What is the process of eukaryote transcription?
Takes place in nucleus, must pass through nuclear membrane to ribosomes in cytoplasm or rough ER-translation
What is the process of transcription in the nucleus?
Cap and tail- added to promote translation, and splicing, intron sequences clipped out from between exons (coding sequences), exons joined together to form continuous coding mRNA.
What is translation?
Rendering message from one language to another, moving an object from one place to another. mRNA moves from transcription site to the site where codons get read and amino acids polymerized. Information encoded on mRNA is rendered into sequence of amino acids.
What is transfer RNA?
Interface between amino acid pool in cytoplasm and RNA sequence along length of mRNA. Consists of 80 RNA monomers folded into 3D L shape. One end carries anticodon bases, complementary to codon for amino acid on mRNA. Other side is a site for attachment of amino acid specified by codon/anticodon. 20 different forms of enzyme, one for each amino acid.
Ribosomes and Translation
Funtion: protein synthesis, holds mRNA and complementary tRNAs close together, allows for peptide bonds. Two tRNA binding sites and one mRNA binding site.
Ribosomes and Translation: Initiation
Isolated ribosomal small subunit binds mRNA polynucleotide. Start codon of mRNA binds with initiator tRNA in P site. Large ribosomal subunit binds with complex.
Ribosomes and Translation: Elongation
Sequential attachment of appropriate tRNAs to complementary sections of mRNA as it moves along mRNA binding site.
What are the differences between autotrophy and heterotrophy?
Autotrophy: Synthesis of organic molecules from CO2 (photosynthesis, producers)
Heterotrophy: Synthesis of organic molecules obtained from environment (consumers and decomposers)
What are the 4 prokaryote modes of nutrition?
Light and CO2=Photoautotrophs
Chemical and CO2- Exergonic chemical reactions for energy, chemoautotrophs
Light and Organic Compouds=Photoautotrophs
Organic Compounds and Chemicals= Chemoheterotrophs, exergonic chemical reactions for energy
Biofilms
Mono or multi-species films consisting of extracellular proteins. Some evidence of cell-cell communication to modify conditions within the film to favour cell survival-ecological communication.
What are protists?
Mostly unicellular, multiple kingdom. Evolutionary radiations preceded evolution of plants and animals.
Endosymbiotic Hypothesis
Heterotrophic eukaryotes evolved first through union with mitochondrial ancestor prokaryote
Autotrophic eukaryotes evolved from heterotrophic through union with photosynthetic prokaryote.
What is multicellularity?
Specialized mutually independent cells to carry out aspects of various functions of an organism. They communicate with each other. Multicellular organisms can carry out homeostasis, relieving constituent cells of the need. Transition to multicellularity occured independently at least 4 times.
Evolution of multicellularity
Began with flagellated unicellular organism. Begins living as colonies, learn to communicate (most difficult step), cells can specialize.
Kingdom Plantae
Plants are terrestrial- shared derived features are adaptation to terrestrial life. Common ancestor-shallow water multicellular green algae, frequently exposed to air, around 500 million years ago. All photosynthetic (photoautotrophs)
Shared derived features of Kingdom Plantae
Cellulose cell walls, cells connected by plasmodesmota, tissue level of organisation, terrestrial.
Plant Challenges
Have to remain in 1 place, support body against gravity, obtain water and nutrients, resist drying out, moving water against gravity, moving gametes without water, dispersing offspring without water-requires organization at tissue level
Cuticle
Waterproofing layer covering exposed tissues, prevents water loss from stems and leaves.
Stomata
Allows gases to diffuse into interior of plant, have guard cells to reduce water lost.
How does water move through the plant?
Largely absorbed from soil by roots, transported through tissues of body by vascular tissue (xylem and phloem), simple plants have little or no vascular tissue (remain small).
Plants and nutrients
Roots supply nutrients from soil, CO2 for photosynthesis admitted through stomata. Leaves provide extensive surface area for absorption of sunlight.
Plants and Gravity
Lignin associated with cell walls in vascular tissues, stiffens plant bodies. Larger the plant, the more lignin there is.
Reproducing out of water
Pollen grain is a mobile waterproof container for male gametes (borne by wind, animals). Female gametes retained within structure of plant.
