MM_Ch5.2 2024 PDF - Biology Past Paper

5.4 The Nucleoid and Bacterial Cell Division – 1 Section Objectives ▪ Describe how DNA is organized within the bacterial cell. ▪ Explain how DNA replication is coordinated with cell growth and division. 1 Bacterial DNA Is Organi...

5.4 The Nucleoid and Bacterial Cell Division – 1 Section Objectives ▪ Describe how DNA is organized within the bacterial cell. ▪ Explain how DNA replication is coordinated with cell growth and division. 1 Bacterial DNA Is Organized in a Nucleoid ▪ The DNA containing region of the bacterial cell is called the nucleoid. ▪ The nucleoid contains loops of DNA held together by DNA-binding proteins. All the loops connect back to a central point called the origin of replication,” halfway between the two poles. = loops of chromosome 2 Bacterial Cell Division ▪ Bacterial cell division steps DNA replication Protein synthesis and expansion of cytoplasm causes cell to elongate. Septum forms and the cell divides. 3 From: https://microbenotes.com/differences-between-staphylococcus-and-streptococcus/ Bacterial Cell Division - 2 Transcription and translation occur at top speed while the DNA itself is being replicated = rapid protein production. ▪ RNA polymerase: The enzyme responsible for transcription in prokaryotes. ▪ Promoter: The DNA sequence where transcription starts. ▪ Transcription phases: Initiation, elongation, and termination. ▪ Termination signals: Rho- dependent and rho-independent. ▪ Coupling: Transcription, translation, and mRNA degradation can occur simultaneously. 5.5 Specialized Structures of Bacteria – 1 Section Objectives ▪ Describe how pili and stalks enable bacteria to adhere to a substrate where conditions are favorable. ▪ Explain how flagellar motility and chemotaxis enable bacteria to respond to environmental change. ▪ Describe the functions of thylakoids, storage granules, and magnetosomes. 6 Pili and Stalks Enable Attachment Adherence is the ability to attach to a substrate, using specific structures such as pili (protein filaments). Motility is the ability to move and relocate. 7 Pili and Stalks Enable Attachment ▪ Pili (singular, pilus) are made of pilin protein. Fimbriae (short attachment pili) attach cells to surfaces. Conjugation (sex) pilus facilitates transfer of DNA between cells. ▪ Stalks are membranous extensions of cytoplasm that secrete adhesion factors (holdfasts). 8 Rotary Flagella Enable Motility and Chemotaxis – 1 ▪ Multiple flagella ▪ Flagellar motor 9 Rotary Flagella Enable Motility and Chemotaxis – 2 ▪ Chemotaxis involves rotation of the flagella that propels the cell in response to stimuli. 10 Bacterial Structures for Different Habitats ▪ Adaptive structures for diverse environments Thylakoid membranes – Photosynthetic bacteria Gas vesicles – Aquatic bacteria inflate/deflate for buoyancy. Storage granules – Storage of nutrients such as sulfur, phosphate, or PHA Magnetosomes – Store magnetite (iron oxides) for magnetotaxis 11 5.6 The Eukaryotic Cell – 1 Section Objectives ▪ Explain the structure and interconnection of membranous organelles in the endomembrane system. ▪ Describe the functions of the Golgi complex, endoplasmic reticulum, and nuclear membrane. ▪ Explain how the evolutionary process of endosymbiosis led to mitochondria and chloroplasts. ▪ Describe the eukaryotic cytoskeleton. ▪ Describe the motility of eukaryotic flagella and cilia. 12 5.6 The Eukaryotic Cell – 2 13 Organelles of the Eukaryotic Cell ▪ The endomembrane system Rough endoplasmic reticulum (rough ER) Smooth endoplasmic reticulum (smooth ER) Lysosomes Golgi apparatus 14 The Nucleus of a Eukaryote Organizes DNA ▪ The nucleus organizes DNA in chromatin. Nucleus Nuclear membrane Nucleolus 15 Mitochondria and Chloroplasts Yield Energy – 1 ▪ Mitochondria and chloroplasts Mitochondria and chloroplasts have bacterial genomes and ribosomes. Evolved early in the history of life through endosymbiosis Convert energy from food to ATP 16 Mitochondria and Chloroplasts Yield Energy – 2 17 The Cytoskeleton Maintains Shape ▪ Cytoskeleton 18 The Cytoskeleton Maintains Shape ▪ Cytoskeleton Pamer, E., et al., (2004) 19 The Cytoskeleton Maintains Shape ▪ Cytoskeleton 20  Specialized Structures – 1 ▪ Flagella and cilia are constructed of microtubules and consist of bundles of microtubules within thin extensions of the cell membrane. ▪ Eukaryotic flagella are large, containing multiple microtubules enclosed by a membrane (move with a whiplike motion, powered by ATP hydrolysis). ▪ Bacterial flagella consist of a single coiled tube of protein, whose rotary motion is driven by the flagellar motor embedded in the cell envelope. 21 Specialized Structures – 2 ▪ Contractile vacuoles remove water from cells to prevent osmotic shock when lack of a cell wall. 22 Clicker Question 1 Which of the following would be found in BOTH a prokaryotic and eukaryotic cell? a. ribosomes b. mitochondria c. conjugation pilus d. endoplasmic reticulum 23 Clicker Question 2 Which of the following is true of passive diffusion? a. It occurs with the concentration gradient. b. It never involves a protein transporter. c. It occurs against the concentration gradient. d. It always involves a protein transporter. 24 Clicker Question 3 You are investigating the cause of an outbreak of food poisoning. The culprit contains peptidoglycan and lipopolysaccharide. Which of the following organisms could be the cause? a. Staphylococcus aureus, a Gram-positive bacterium b. E. coli, a Gram-negative bacterium c. Aspergillus fumigatus, a fungi d. Any of the above organisms could be the cause. 25 Clicker Question 4 Which of the following is a characteristic of a Gram-positive cell wall? a. waxy due to the presence of mycolic acid b. outer membrane with lipopolysaccharide c. thick with several layers of peptidoglycan d. periplasmic space between membrane and peptidoglycan 26 Clicker Question 5 A eukaryotic cell with defective lysosomes would have difficulty a. generating ATP from respiration. b. synthesizing proteins. c. digesting food particles. d. replicating DNA. 27