cell structure and function

• Selected permeability is a direct consequence of membrane structure.
• The cell membrane is selectively permeable, allowing small nonpolar molecules like n2, O2, and CO2 to pass freely, while hydrophilic substances like large polar molecules and ions cannot move across the membrane without help through transport proteins.
• There are two types of transport proteins: channel proteins and carrier proteins.
• Channel proteins are hydrophilic tunnels spanning the membrane that allow specific target molecules to pass through.
• Carrier proteins span the membrane and change shape to move a target molecule from one side of the membrane to another.
• Small polar molecules like water can pass directly through the membrane but in minimal amounts.
• The cell wall is a structural boundary and permeable barrier that protects and maintains the shape of the cell, prevents against cellular rupture when internal water pressure is high, and helps plants stand up against the force of gravity.
• The cell wall has plasmodesmata which are small holes between plant cells that allow the transfer of nutrients, waste and ions.
• Selectively permeable membranes allow for the formation of concentration gradients, which are when a solute is more concentrated in one area than another.
• Passive transport is the net movement of molecules from high concentration to low concentration without metabolic energy needed, and plays a primary role in the import of materials and the export of waste.
• There are two types of passive transport: diffusion and facilitated diffusion.
• Diffusion is the movement of molecules from high concentration to low concentration where non-polar substances pass freely.
• Facilitated diffusion is the movement of molecules from high concentration to low concentration through transport proteins allowing for hydrophilic molecules and ions to pass through membranes.
• Active transport requires energy to move molecules from regions of high concentration to regions of low concentration.
• Endocytosis requires energy to move large molecules into the cell.
• Making macromolecules and particulate matter by forming new vesicles derived from plasma membranes is a type of endocytosis called phagocytosis.
• Exocytosis requires energy to move large molecules out of the cell and exocytosis internal vesicles use energy to fuse with the plasma membranes and secrete large macromolecules out of the cell.
• All living cells contain a genome and ribosomes.
• Ribosomes synthesize proteins according to mRNA sequence.
• Endoplasmic reticulum is a subcellular structure that is membrane enclosed.
• Endoplasmic reticulum is a network of membrane tubes within the cytoplasm of eukaryotic cells.
• The rough eR has ribosomes attached to its membrane and it compartmentalizes the cell.
• The smooth ER does not have attached ribosomes and its functions include detoxification and lipid synthesis.
• The Golgi complex is involved in the correct folding and chemical modifications of newly synthesized proteins and packaging for protein trafficking.
• The mitochondria has a double membrane.
• The afternoon membrane of the mitochondria is smooth and the inner membrane is highly convoluted, forming folds called Cristae.
• Mitochondria functions in production of ATP energy that eukaryotic cells can use for cell work.
• Vesicles are membrane enclosed sacks found in some eukaryotic cells that contain hydrolytic enzymes.
• Hydrolytic enzymes can be used for digesting a variety of materials such as damaged cell parts or macromolecules.
• Vacuoles are membrane bound sacs found in eukaryotic cells, ranging from storage of water and other macromolecules to release a waste from a cell.
• Chloroplast is found in eukaryotic cells, it has a double outer membrane and it's specialized for capturing the energy from the Sun and producing sugar for the organism.
• Thylakoids are highly folded membrane compartments that are organized in Stacks called Grana, they contain chlorophyll pigments that comprise the photosynthesis and light dependent reactions.
• The stroma is a distinct component of chloroplast, it is the fluid between the inner chloroplast membranes and outside the thylakoids, carbon fixation reactions occur here.
• The mitochondria's double membrane provides compartments for different metabolic reactions, mitochondria capture energy from macromolecules, the Krebs cycle reactions occur in the Matrix of the mitochondria, electron transport and ATP synthesis occur in the inner mitochondrial membrane.
• Vacuoles play a variety of roles including storage and release of water macromolecules and cellular waste products.
• Plants vacuoles aid in retention of water for turgor pressure.
• Lysosomes contain hydrolytic enzymes and can contribute to cell function in the following ways: intracellular digestion, recycling of organic materials and programmed cell death, apoptosis.
• Glycoproteins are one or more carbohydrates attached to a membrane protein.
• Cholesterol regulates bilayer fluidity under different environmental conditions.
• There are two types of embedded proteins: Peripheral proteins and integral proteins.