what are characteristics of living organisms?
Movement Respiration Sensitivity Growth Reproduction Excretion Nutrition
Cell Membrane
Thin, partially permeable boundary around cytoplasm. Controls entry & exit of substances. Maintains cell contents and internal environment.
Cytoplasm
Jelly-like fluid (90% water, with salts, sugars, proteins, enzymes).
Site of many chemical reactions. Contains organelles (mitochondria, ribosomes, etc.)
Nucleus
Nucleus
Rounded structure enclosed by a nuclear membrane.
Contains DNA (chromosomes). Controls cell activities, enzyme production, determines cell type and cell division.
Mitochondria
“Powerhouse of the cell”. Site of aerobic respiration → energy (ATP) release for cell processes
Ribosomes
Very small organelles. Site of protein synthesis.
Extra organelles in plant cells
Cell wall, Chloroplast, Large Permanent Vacuole
Cell Wall
Made of cellulose (non-living, freely permeable to water and dissolved substances).
Provides shape & support. Prevents bursting.
Chloroplasts
Contain chlorophyll → trap light for photosynthesis (makes glucose).
Large Permanent Vacuole
Fluid-filled sac with cell sap (sugars, salts, pigments, water).
Maintains firmness (turgor pressure) and stores substances.
Bacterial Structure has what organelles?
Cell wall, cell membrane, cytoplasm, ribosomes, circular DNA, plasmids
Cell wall of Bacteria
Provides shape & protection.
Made of peptidoglycan
Prevents cells from bursting in dilute solutions.
Cell membrane in bacteria
Lies just inside the wall.
Controls entry and exit of substances.
Site of some respiration enzymes (since no mitochondria).
Circular DNA in Bacteria
Single, long circular molecule of DNA.
Lies free in cytoplasm (no nucleus).
Controls cell activities and reproduction.
EUKARYOTES
Plasmids
Small extra loops of DNA
Carry additional genes (e.g. antibiotic resistance).
Can be passed between bacteria.
Cell dividsion
New cells are always produced by the division of existing cells-cell theory.
Growth → increase in number of cells.
Repair → replacement of damaged or dead cells.
Reproduction → formation of gametes or new organisms (depending on type of division)
