Cell Structure and Function - Fall 2024

Cell Structure and Function  What Is a Cell? ▪ Cell The smallest unit that shows the properties of life ▪ All cells have a plasma membrane and cytoplasm, and all start out life with DNA ▪ Eukaryotic cell Cell interior is divided into functional compartments, including a nucleus ??...

Cell Structure and Function  What Is a Cell? ▪ Cell The smallest unit that shows the properties of life ▪ All cells have a plasma membrane and cytoplasm, and all start out life with DNA ▪ Eukaryotic cell Cell interior is divided into functional compartments, including a nucleus ?? ▪ Prokaryotic cell Small, simple cells without a nucleus ??  Introducing Eukaryotic Cells ▪ Eukaryotic cells have a true nucleus. (a DNA region surrounded by a nuclear envelope). ▪ Eukaryotic cells carry out much of their metabolism inside membrane- enclosed organelles. ▪ Organelle A structure that carries out a specialized function within a cell.  Introducing Prokaryotic Cells Bacteria are prokaryotes (“before the nucleus”), the smallest and most metabolically diverse forms of life (The DNA region is NOT surrounded by a nuclear envelope). This region of DNA is called NUCLEOID flagellum capsule cell wall plasma membrane cytoplasm, with ribosomes DNA in nucleoid pilus General Prokaryote Body Plan ▪ Cell wall surrounds the plasma membrane Made of peptidoglycan( a large polymer that forms a mesh-like scaffold around the bacterial cytoplasmic membrane, and it is coated with a sticky capsule ▪ Flagellum for motion ▪ Pili help cells move across surfaces Sex pilus aids in sexual reproduction Prokaryotic and Eukaryotic Cells All Cells Have Three Things In Common ▪ Plasma membrane Controls substances passing in and out of the cell ▪ DNA containing region Nucleus in eukaryotic cells Nucleoid region in prokaryotic cells ▪ Cytoplasm A semifluid mixture containing cell components An Animal Cell A Plant Cell  The Nucleus ▪ The nucleus keeps eukaryotic DNA away from potentially damaging reactions in the cytoplasm ▪ The DNA never leaves the nucleus !!  The Nuclear Envelope ▪ Nuclear envelope Two lipid bilayers pressed together as a single membrane surrounding the nucleus Outer bilayer is continuous with the ER Nuclear pores allow certain substances to pass through the membrane The Nucleoplasm and Nucleolus ▪ Nucleoplasm Viscous fluid inside the nuclear envelope, similar to cytoplasm ▪ Nucleolus A dense region in the nucleus where subunits of ribosomes are assembled from proteins and RNA Chromosome Condensation  The Chromosomes ▪ Chromatin All DNA and its associated proteins in the nucleus ▪ Chromosome A single DNA molecule with its attached proteins During cell division, chromosomes condense and become visible in micrographs Human body cells have 46 chromosomes  4. The Endomembrane System ▪ Endomembrane system Makes lipids, enzymes, and proteins for secretion or insertion into cell membranes  The Endoplasmic Reticulum ▪ Endoplasmic reticulum (ER) An extension of the nuclear envelope that forms a continuous, folded compartment ▪ Two kinds of endoplasmic reticulum Rough ER (with ribosomes) folds polypeptides into their tertiary form Smooth ER (no ribosomes) makes lipids, breaks down carbohydrates and lipids, detoxifies poisons Vesicles ▪ Vesicles Small, membrane-enclosed saclike organelles that store or transport substances ▪ Peroxisomes Vesicles containing enzymes that break down hydrogen peroxide, alcohol, and other toxins ▪ Vacuoles Vesicles for waste disposal  Golgi Bodies and Lysosomes ▪ Golgi body A folded membrane containing enzymes that finish polypeptides and lipids delivered by the ER Packages finished products in vesicles that carry them to the plasma membrane or to lysosomes ▪ Lysosomes Vesicles containing enzymes that fuse with vacuoles and digest waste materials The Endomembrane System The Endomembrane System  4. Lysosome Malfunction ▪ Different kinds of molecules are broken down by different lysosomal enzymes One lysosomal enzyme breaks down gangliosides, a kind of lipid!!  Tay Sachs Disease ▪ In Tay Sachs disease, a genetic mutation alters the lysosomal enzyme that breaks down gangliosides, which accumulate in nerve cells Affected children usually die by age five  Mitochondria ▪ Mitochondrion Eukaryotic organelle that makes the energy molecule ATP through aerobic respiration Contains two membranes, forming inner and outer compartments; buildup of hydrogen ions in the outer compartment drives ATP synthesis Has its own DNA and ribosomes Mitochondrion Plastids ▪ Plastids Organelles that function in photosynthesis or storage in plants. ▪ Chloroplasts Plastids specialized for photosynthesis The Chloroplast  The Central Vacuole ▪ Central vacuole A plant organelle that occupies 50 to 90 percent of a cell’s interior Stores amino acids, sugars, ions, wastes.  4. The Dynamic Cytoskeleton ▪ Eukaryotic cells have an extensive and dynamic internal framework called a cytoskeleton ▪ Cytoskeleton An interconnected system of many protein filaments – some permanent, some temporary Parts of the cytoskeleton reinforce, organize, and move cell structures, or even a whole cell  Cilia, Flagella, and False Feet ▪ Eukaryotic flagella and cilia Whiplike structures formed from microtubules. Grow from a centriole which remains in the cytoplasm as a basal body ▪ Pseudopods “False feet” used by amoebas and other eukaryotic cells to move or engulf prey  Moving Cells ▪ Flagellum of the human sperm, and pseudopods of a predatory amoeba Stay Safe , Healthy and Happy