CELL BIOLOGY (WEEK 2)

What are all the parts of a eukaryotic cell?

• cytoplasm

• plasma membrane

• nuclear envelope

• nucleolus

• nucleus

• nuclear pore

• rough er

• smooth er

• centrosome

• ribosome

• mitochondrian

• lysosome

• golgi complex

• cilia

• peroxisome

What are the properties of DNA?

• holds genetic code

• double stranded

• consists of deoxyribose sugar, phosphate group, and the nitrogenous bases (A, T, G, C)

What are the properties of RNA?

• involved in protein synthesis (mRNA, tRNA, rRNA)

• single stranded

• consists of ribose sugar, phosphate group, and nitrogenous bases (U, A, G, C)

What is the central dogma of life?

• DNA does replication + requires enzymes (proteins)

• transcription of DNA to RNA

• translation of RNA to proteins

What occurs during DNA replication?

• DNA must be copied for cell division

• old DNA strands act as templates for new strands

• DNA polymerase is the enzyme that makes DNA copies

What occurs during the transcription of DNA to RNA?

• portion of DNA is copied into complementary messemger RNA molecule via RNA polymerase

• mRNA moves from nucleus to cytoplasm to ribosome

What occurs during RNA translation?

• mRNA sequencec is translated into amino acid on the ribosome; produces polypeptide

• the mRNA sequence is called a codon and is read 3 nucleotides at a time

• codons code for a particular amino acid

• tRNA matches the mRNA sequence to the amino acid

What are the parts of an amino acid?

• amino group

• carboxyl group

• r group / side chain

How can we compare prokaryotes and eukaryotes?

• eukaryotes are larger at 10-100 um; prokaryotes are smaller at 1-10 um

• both contain carbohydrates, proteins, nucleic acids, and lipids

• eukaryotes have multiple and linear chromosomes found in the nucleus

• prokaryotes have single, circular chromosomes found in the nucleoid; can also contain plasmids

What is a plasmid?

• small circles of DNA that do not encode essential genes

How does eukaryote cell division occur?

• mitosis which consists of 4 phases

• requires a mitotic spindle

How does prokaryote cell division occur?

• binary fission where equal division of a bacterial cell into two cells occurs

How does eukaryote genetic variation occur?

• meiosis

• crossing over

• independent assortment

How does prokaryote genetic variation occur?

• horizontal gene transfer from the same generation

What is transformation?

• bacteria collect DNA fragments (from lysed bacterial cells) in their environment

• integrates fragments into bacteria’s own dna

What is transduction?

• genetic transfer between bacterioa using a bacteriophage

  • bacteriophage = viruses that infect bacteria

What is conjugation?

• DNA is directly transferred from one bacterium to another which requires direct cell to cell contact

• happens via pilus or mating bridge

What traits do bacteria acquire by HGT?

• antibiotic resistance

• toxins like shiga

• ability to use different nutrients like galactose fermenting enzyme

How can we compare organelles in eukaryotes and prokaryotes?

• eukaryotes have organelles like mitochondria or choroplast

• prokaryotes have no organelles

How can we compare ribosomes in eukaryotes and prokaryotes?

• eukaryotes have free and bound ribosomes

• prokaryotes have smaller and less dense + free form ribosomes only

What do eukaryotes contain in their plasma membranes?

• phospholipid bilayer

• cholesterol which is important for membrane stability, fluidity, and permeability

• has channels that allow for osmosis, active transport, facilitated diffusion, etc

What do prokaryotes contain in their plasma membranes?

• phospholipid bilayer

• no cholesterol or sterols

• can use osmosis, active transport, and facilitated diffusion

How can we compare the cell walls of eukaryotes and prokaryotes?

• eukaryotes vary as some may have none, cellulose, silica (algae), or chitin (fungi)

• prokaryotes has cell walls made of peptidoglycan

What is peptidoglycan?

• made up of n-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM)

• contains side chains of amino acids between NAG and NAM

• cross bridge amino acids

What are the names of chains / bonds in the peptidoglycan?

• peptide chain

• glycosidic bond

• cross linking

What is a gram positive bacteria?

• thick peptidoglycan layer

• has techoic acids that aid in cation transport, cell wall structure, and antigenic specificity

• stains purple with gram stain

What is a gram negative bacteria?

• thin peptidoglycan layer

• outer membrane with lipopolysaccharides (LPS), lipoproteins, porins, and phospholipids

• stains pink with gram stain

What is the difference of susceptibility in gram positive and gram negative bacterias?

• gram positive bacteria are more susceptible to antibiotics and disinfectants (eg. staphylococcus and streptococcus spp.)

• gram negative bacteria are less susceptible to antiobiotics and disinfectants (eg. escherichia coli, salmonella spp.)

What is glycocalyx?

• sticky carbohydrate layer present in prokaryotes and eukaryotes BUT with different functions

How can we describe the glycocalyx in a eukaryote?

• carbohydrates bond proteins and lipids in plasma membrane

• functions to strengthen cell surface, attach cells together, and in cell to cell recognition

How can we describe the glycocalyx in prokaryotes?

• carbohydrates outside cell wall with similar functions

• has a capsule that is an organized and firmly attached; helps bacteria avoid phagocytosis

• has a slime layer that is disorganized and loosely attached

What is the importance of movemnent?

• allows for cells to find mates

• find favourable conditions away from danger or a palce with optimal conditions for cellular functions

• reach new environments which reduces competition and increases odds of survival

What is taxis?

• movement of a cell

• phototaxis for light response

• thermotaxis for temp response

• chemotaxis for nutrient / chemical response (follows gradient)

What is positive and negative taxis?

• positive: cell moves towards stimulus

• negative: cell moves away from stimulus

What is a flagella?

• long flexible tail found at one side of a cell

What is a cilia?

• multiple small and short projections on the cell

What is atrichous?

• no flagella

What is peritrichous?

• flagella all over the cell

What is a polar flagella?

• flagella at one or both ends

• monotrichous = at one end

• amphitrichous = at both ends

• lophotrichous = a bunch at one end

How does running or swimming occur in a prokaryote?

• flagella moves counter clockwise to propel bacteria in one direction

How does tumbling occur in a prokaryote?

• the flagella splay out and move clockwise preventing forward movement

• allows for change of direction

How does swarming occur in a prokaryote?

• rapid wave like movement in peritrichous bacteria

What are endospores?

• gram positive cells only (and only prokaryotes)

• one bacteria forms one endospore

• highly durable and dehydrated cells that survive harsh environments

• can be released into environment via sporulation

• can revert to a vegetative / growing state

What is a fimbriae?

• only in prokaryotes

• short appendages that enable attachment rather than movement

• present in biofilm formation

• adhesion to epithelial cells can cause disease

• can consist of a few to hundreds

What is a pilus?

• long hair like appendages used for motility and dna transfer

• only one to two per cell

• only in prokaryotes

What are inclusions?

• reserves found in prokaryotes that contain certain nutrients for use when in extreme environments

What are axial filaments / endoflagella?

• prokaryotes only

• found mostly in spiral shaped bacteria + inside bacterial cell

• causes spiral / corkscrew motion