Structures and Functions of Eukaryotic Cells Animal Cell Plant Cell Nucleus • Contains DNA, which stores and copies genetic info • DNA forms chromosomes • Structures in the nucleus: – Nucleolus (contains RNA and proteins) – Nuclear envelope (has pores in its double phospholipd bilayer that allow some particles to pass through) Endoplasmic Reticulum • Membranous bound tubules • Rough ER has ribosomes attached that make proteins • Smooth ER makes lipids and phospholipids, detoxifies drugs/alcohol, makes hormones. Golgi Apparatus • Stack of curved membrane sacs • Works with nuclear envelope, ER and vesicles as a part of a protein and lipid modification and transport system. • Initial proteins/lipids are made by the ER and sent in a vesicle to the Golgi • Proteins/lipids are stored or further modified • Proteins/lipids are pinched off to form vesicles that will exit the cell or go to another spot in that cell. • In animal cells the Golgi also produces lysosomes Lysosomes • membrane bound sacs that have digestive enzymes in them • Catalyze hydrolysis reactions • Breaks down macromolecules • Acidic inside (pH of 5) Peroxisomes • Membrane-bound sacs containing enzymes • Form from budding off the ER • Catalyze redox reactions • Breaks down some toxic molecules, such as alcohol. Vesicles and Vacuoles • Vesicle: term used to describe membrane-bound sacs used for transportation throughout the cell • Vacuole: central large vesicle found in plant cells that contains water, enzymes, ions, sugars, amino acids. • The vacuole helps give the plant shape through turgor pressure Chloroplasts • Found in plant cells • Contain chlorophyll that absorbs sunlight energy during photosynthesis • Has a thick liquid called the stroma inside • Inner membrane surrounds many flattened disks called thylakoids • Many thylakoids are stacked on top of each other to form a granum (pl. grana) • Contain their own DNA Mitochondria • Break down molecules for energy • 2 membranes • Inner membrane is folded and called the cristae • Space inside the inner membrane is called the matrix. • Contain their own DNA Cell Wall • Plants, fungi and some protists have a cell wall • Provides structure and support • Plant cell walls are comprised of cellulose • Fungi cell walls are made of chitin Cytoskeleton • Internal network of fibres throughout the cytoplasm • Provide structure and anchoring for cell membrane and organelles • Types: – Microtubules: thickest, shape, help with cell division, movement of organelles – Intermediate filaments: shape, anchor organelles and scaffolding of nucleus – Microfilaments: thinnest, shape, muscle contractions, cell division Cilia and Flagella • Flagella are longer, maybe only one or two • Cilia are shorter and there are many • Help with movement of cell Cell Membrane • Regulates the passage of molecules and ions into and out of the cell. • The model we use is called the fluid mosaic model which contains the phospholipid bilayer, integral proteins, cholesterol and carbohydrate groups attached to lipids or proteins (glycolipids, glycoproteins) • Because the phospholipids are held together through weaker intermolecular bonds, they can move around freely. Fluidity of a Membrane • Should maintain its fluidity because if too fluid, it lets too many molecules into the cell. • Temperature, presence of double bonds in the fatty acid tails (more double bonds = not as tightly packed) and length of fatty acid tails (longer chain = more intermolecular interactions) can contribute to fluidity. • Presence of cholesterol decreases fluidity at room temperature by increasing intermolecular forces. Cholesterol can increase fluidity at lower temperatures by breaking up the tight packing of the phospholipids. Membrane Proteins • Integral proteins are embedded in the membrane. • Peripheral proteins are more loosely attached to the inside of the membrane. • They help to stabilize the cell and give it shape by connecting to the cytoskeleton • Transport: move substances across the membrane • Catalyst: work as enzymes • Cell recognition: carb chains enable cells to recognize each other • Signal reception and transduction: receptor proteins bind to signal molecules such as hormones and can send signals elsewhere. Practice: Page 42 # 1, 5, 8, 9.