Bio Chap 2 Flashcards
What is Robert Hooke’s cell theory?
- All living organisms have 1+ cell 2. Cells are most basic unit of life. 3. All new cells are products of pre-existing, living cells
Describe mitosis
Prophase - nuclear membrane dissolves, chromatin condenses into chromosomes, spindle apparatus forms, spindle fibers attach chromosomes kinetochore - centrosome and fibers make up aster.
Metaphase -chromosomes align along metaphase plate
Anaphase - centrosomes pull sister chromatids to opposite sites
Telophase + cytokinesis - nuclear membrane reforms and cells separate.
Describe meiosis
Prophase 1 - nuclear membrane dissolves, chromosomes form chromatin condensing and spindle apparatus forms, homologous chromosomes pair via synapsis. Homologous chromosomes pair by synaptonemal complex - since each pair has 4 chromatids - tetrads. Chromatids can undergo crossing over if once - single crossover event, twice double crossover event. The spot where crossing over occurs is chiasma
Metaphase I - homologous chromosomes align along metaphase plate
Anaphase I - sent to opposite sides of cells
Telophase I and cytokinesis - cell splits into 2 cells
Meiosis II has same steps as mitosis.
What are the 3 key differences between mitosis and meiosis?
- Cells undergoing meiosis have 2n but produce n daughter cells. Mitosis 2n → 2n
- Meiosis only occurs in germ cells and mitosis in somatic
- Homologous chromosomes pair up and crossing over occurs. In mitosis - just sister chromatids.
What is cell cycle?
G1, S, G2, M Interphase is G1-G2
- G1 - cell produces organelles to prep for division - check to make sure that has correct complement of DNA
- S - cell undergoes DNA replication
- G2- cell checks to see if ready for division - ensuring DNA synthesis occurred properly and there is enough cytoplasm and organelles to divide.
What happens when checkpoints cail?
When checkpoints fail, cancer can occur - often as a result of genetic causes - mutagens - agents that cause DNA mutations. Oncogenes - genes that can promote cell division when overexpressed - result of mutations in proto-oncogenes which have normal functions. Require mutation in only one allele to lead to dysfunctional cell growth. Tumor suppressor genes - can give rise to cancer when mutation inactivates them - mutations at both alleles.
What shapes are prokaryotic cells?
cocci, bacilli or spirilli
What are anaerobes?
bacteria that don’t need oxygen - aerobes do.
What are obligate anaerobes?
organisms that require absence of oxygen
What are aerotolerant anaerobes?
can only engage in anaerobic metabolism but oxygen is not toxic.
What are obligate aerobes?
Require oxygen
What are facultative anaerobes?
Prefer to not have oxygen
What are facultative aerobes?
Prefer to have oxygen but can live without.
Describe bacterial cell wall
Bacteria have cell wall - some have layer surrounding it called capsule - sticky layer of polysaccharide goo that may surround entire colony - allowing them to survive in animals. Peptidoglycan - most important component of cell wall - cross-linked chains of sugars and amino acids - unique to prokaryotes - target of many antibiotics.
How are peptidoglycan levels differentiated?
Gram staining - crystal violet dye to heat-fixed bacteria, adding iodide to trap dye to peptidoglycan layer, washing culture with ethanol or acetone to remove lipopolysaccharide membrane in Gram-negative bacteria and applying counterstain to visualize Gram-negative bacteria - Gram-positive appear dark purple and negative appear pink.
What is gram positive vs. negative? (See images)
Gram-positive - thick layer of peptidoglycan outside membrane. Gram-negative - have only thin layer in cell wall. Also have outer membrane with lipopolysaccharide. Gram-negative have resistance to antibiotics.
What other role do prokaryotic cell membranes play?
Cell membrane also plays role in prokaryotic aerobic respiration - relies on ETC and ATP synthase via cell membrane.
What is the difference between prokaryotic and eukaryotic ribosomes?
Prokaryotic ribosomes have 30S and 50S subunit that combine to make 70S ribosome - eukaryotes have 40S and 60S to make 80S ribosome. S is Svedberg unit - sedimentation rate of ribosomes.
What are flagella important for?
chemotaxis - movement of bacterium based on chemical signals. There are chemoreceptors on surface of cell that bind attractants or repellents and these molecules dictate which way flagella rotates and which direction bacteria moves.
What are pili?
long projections on surface that help bacteria attach to surfaces. There is a sex pilus that helps male attach to female and form conjugation bridges.
How is DNA stored in prokaryotes?
DNA stored on single circular chromosome in nucleoid region of cell. Some bacterial also have small circular DNA pieces called plasmids- often code for advantageous traits in bacteria.
Describe the process of binary fission
Formation of two identical cells.
- Replication - chromosome and plasmid are duplicated.
- Segregation - each chromosome is pulled to ne side and new cell wall begins to form in middle
- Seperation - two cells have fully formed cell wall and pull away
Describe prokaryotic cell growth stages (see image)
Lag phase - when bacteria are adapting to new environment.
Log phase - certain number of resources which causes number of bacteria to level off in period known as stationary phase.
Death phase - no more resources left in environment.
Bacterial growth is positive feedback loop
What aid with antibiotic resistance and what 4 mutations during binary fission help?
Capsule and plasmid DNA help. Possibility of mutations during binary fission also.
4 types of these mutations:
- Formation of new enzymes in bacteria that deactivate antibiotic before it is effective
- Mechanism allowing bacteria to eject antibiotics from bacteria - rendering them useless
- Changes cell wall and prevents antibiotics from entering
- Alters function of bacteria that an antibiotic targets