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56 Cards in this Set
- Front
- Back
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Four key features of living things
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1) Genome to encode information
2) Ribosomes to synthesise proteins 3) Proteins to do work 4) A membrane to keep all the components together |
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How do viruses differ from true living things?
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- They have no ribosomes (all of their proteins ae synthesised on host ribosomes)
- No permanent membrane (which would separate the viral genome from the host ribosomes) |
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The three domains that true cellular life forms fall into.
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Bacteria
Archaea Eukarya |
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Lateral Gene transfer
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transfer of genes other than from parent to offspring
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Differences in the small subunit ribosomal RNA in bacteria, archaea and eukaryotes.
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Bacteria and archaea have 16S rRNA;
Eukaryotes have 18S rRNA. |
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Basic unit for microorganisms
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Strain
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Common property of viruses
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Lacking ribosomes and needing to use host ribosomes to produce their proteins.
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Where is the genome contained in a virus?
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Capsid.
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What are the 5 forms of genome in viruses?
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DS DNA
SS DNA DS RNA SS RNA RNA replicated |
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What are the subunits of capsid?
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Capsomeres
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What are two most common ways capsomeres are arranged in?
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- Helical (filamentous viruses)
- Icosahedron (icosahedral viruses) |
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Two ways that viruses escape from the host cell.
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Budding - acquire a membrane derived from the host cell membrane (enveloped)
Lysis - bursting...don't acquire a membrane (non-enveloped) |
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General virus life cycle
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- Protein on the virus surface binds to a receptor on the host cell surface.
- Taken into the cell - Disassembles and releases the genome and any packaged enzymes. - Early expression -> genome replication - Late expression -> capsid formation - released through either budding or lysis. |
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What is the bacterial cell wall made of?
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Peptidoglycan
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Function of the cell wall.
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Structural support -> resist bursting due to osmosis (load bearing structure)
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Distinguish between gram positive and gram negative bacteria.
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Gram positive: have a thick cell wall, probably formed of peptidoglycan strands. Twisted to form cables which are wrapped around the cell outside the cell membrane.
Gram negative: have a thin layer of peptidoglycan around the cell membrane. Surrounded by a second membrane, the outer membrane. |
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Form of DNA in bacteria.
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Single circular chromosome
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Where is the DNA contained in bacteria?
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tightly compacted by proteins and forms a nucleoid in the center of the cell.
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Basic structure of a rod shaped bacteria.
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Cylindrical tube of peptidoglycan with two hemispherical end-caps (poles).
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Outline the growth process in bacteria
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- Occurs by elongation of the tube.
- Deposition of new cell wall material in a helical pattern directed by a protein called MreB, - DNA is replicated as the tube grows. - When the chromosome is replicated and the tube long enough, the two nucleoids spring apart to create a gap in the centre of the cell. - Z-ring of protein RtsZ forms in the centre of the cell and contracts --> formation of two new end-caps to make two separate cells. |
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What are spherical bacteria called and what are their characteristics?
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They are called cocci, they lack the tube part and consist only of end-caps.
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Describe filamentous bacteria
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Elongate, produce new nucleoidsbut do not divide into separate cells
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Describe vibrios
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curved rods
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Describe Spirilla
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long helical rods
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Describe actinobacteria
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Grow from the tip rather than by elongation of the tube. Can form a branched fungus-like mycelium.
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Which structure helps bacteria swim?
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Flagella
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What are the short protein filaments that many bacteria use to attach to surfaces?
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Fimbriae
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Functions of pili
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- In Conjugation (mating), pili transfer DNA
- For moving around on surfaces |
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Functions of capsule
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Many Bacteria are surrounded by capsule, which prevent them from drying out or being eaten by white blood cells, or to attach to surfaces.
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Which kind of bacteria form endospore and what are its functions?
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Some gram positive bacteria form endospores, which are resistant to heat and drying out, and can sruvive for many years in a dormant state.
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Strictly aerobic
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Require oxygen
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Facultatively anaerobic
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Use oxygen if present but also grow without it
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Aerotolerant anaerobic
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tolerate it but do not use it
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Strictly anaerobic
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killed by oxygen
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Outline the process of how bacteria in nature grow as biofilms attached to surfaces.
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1) Swimming cells with flagella are attracted to food-bearing surfaces,
2) Attach to the surface, move around in large groups, 3) Settle down to form a microcolony, 4) Grow to form a mature biofilm with a complex 3D structure, which releases new swimming cells. |
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Can bacteria engulf solid objects?
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No, but they absorb nourishment through the cell membrane.
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Heterotrophic
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Assimilate organic molecules (sugars and amino acids)
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Autotrophic
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Reducing CO2 as a source of carbon. More diverse CO2 fixation pathways in plants.
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Chemoautotrophic
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Derive energy by oxidizing inorganic substances (H2, H2S, CO, NH3, NO2(-), Fe(2+)).
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Chemoheterotrophic
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Derive energy by oxidizing organic molecules
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Photoautotrophic
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Use light energy and assimilate CO2, such as cyanobacteria, and are ancestral to plant chloroplasts.
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What do most gram negative bacteria belong to? and which five subgroups is it divided into?
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Proteobacteria, divided into Alpha, Beta, Gamma, Delta, and Epsilon.
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Are most cyanobacteria gram-positive or gram-negative?
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Gram negative
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Escherichia Coli
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- Gram negative rod of the Gammaproteobacteria
- Some strains can cause food poisoning and urinary tract infections. |
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Staphylococcus aureus
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- Gram positive coccus of the Firmicutes.
- Can cause serious skin and wound infections. Major problem in hospitals, especially in its antibiotic resistant form, MRSA (Methicillin-resistance Staph. aureus) |
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3 major well studied groups of Archaea
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1) Extreme halophiles: aerobic, live in saturated salt solutions;
2) Methanogens: strict anaerobes, produce energy only by producing methane; 3) Hyperthermophiles: live in very hot environments, often acidic, metabolism often based on sulfur compounds. |
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General features of eukaryotes
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- Endomembrane system that divides the cell into compartments.
- Cytoskeleton of fibres and girders to provide structure. - Actin microfilaments underlies the cell membrane and allows the cell to change shape, exending projections (pseudopodia). Also allows the cells to engulf solid objects. |
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Eukaryotes are more complex because they contain microtubules, what are their functions
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Segregate the chromosomes when the cells divide, allow the genome to be more complex than in bacteria and archaea.
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Compare bacterial and eukaryotic flagella.
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Bacterial flagella are helical protein structures, and rotate like propellers to drive the cell forward.
Eukaryotic flagella beat like whips and contain microtubules. |
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How can a diploid zygote be formed?
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Fusion of two haploid cells.
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Evidence that indicates mitochondria are derived from bacteria of Alphaproteobacteria.
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Mitochondria contain a small circular chromosome and some ribosomes of bacterial type.
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What are the main morphological groups of protozoa and motile algae
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Amoebas, flagellates, ciliates, and apicomplexans (sporozoans).
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How can amoebas move or capture prey?
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By extending pseudopodia
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What are the large broad pseudopodia in lobos amoebas called?
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Lobopodia
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Describe flagellates
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Swim using flagella. The most common pattern: to have two flagella at the front of the cell.
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Dinoflagellates
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Have two flagella which lie in grooves in the cell surface, one helical one being wrapped around the waist so they rotate as they swim.
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