SEF045 Biology - Cell Membrane Structure & Function PDF

**[SEF045 -- Biology - Cell Membrane Structure & Function]** **Prokaryotes** -- no membrane bound nucleus: - Archaea - Bacteria **Plasma Membrane:** - Barrier - Transport - Signalling - Recognition **DNA** -- Deoxyribose Nucleic Acid: A blue rectangle with...

**[SEF045 -- Biology - Cell Membrane Structure & Function]** **Prokaryotes** -- no membrane bound nucleus: - Archaea - Bacteria **Plasma Membrane:** - Barrier - Transport - Signalling - Recognition **DNA** -- Deoxyribose Nucleic Acid: A blue rectangle with black text Description automatically generated **Nitrogenous bases** may be either purines or pyrimidines.  A diagram of a dna strand Description automatically generated All living things contain DNA. However, how that DNA is packaged and formed into nuclear material may differ greatly. Nuclear material is packaged differently in eukaryotes. **Endoplasmic Reticulum** - Continuous folding of nuclear membrane. - Covered in ribosomes (rough). - Folds, modifies and transports proteins. - Smooth ER may form and transport lipids. **Ribosomes** are made of rRNA (ribosomal). Both eukaryotic and prokaryotic ribosomes contain one large and one small subunit. They are differentiated by the unit 'S', this is the 'sedimentation coefficient', how fast they move in a centrifuge. **Golgi Apparatus** - The 'shipping centre' of the cell. - 'Sorts, packages and distributes...' - Secretory vesicle or lysosome.  **Lysosome** - Created by GA - Contains hydrolytic enzymes - Breaks down foreign particles or unneeded parts of the cell. **Mitochondria:** 'Powerhouse' of the cell. - Energy gradient across inner and outer membrane has potential to produce ATP. - Cristae and matrix provides a large surface area to carry out 'respiration'. - Numbers of mitochondria per cell may differ greatly - Mitochondria contains its own genome (circular, like prokaryotes). **Chloroplast:** - Similar to mitochondria, they produce energy for the cell - Utilise light rather than chemical energy - Pigment chlorophyll (in thylakoid membrane) captures light. - Similarly uses energy gradient to produce ATP by exciting an electron. - Own genetic and protein material. **Vacuole** - Large fluid filled sac that helps with structure. - Can often contain: - Water - Sugar - Salts - Pigments - Toxic material. - Animal cells can contain vacuoles, but they are much smaller in size and play less of a role. **The Cytoplasm and its cytoskeleton** A diagram of a human body Description automatically generated **Actin Filaments** - 7nm in diameter - Long and flexible - Can form mesh - They can aid movement by attaching to proteins called motor molecules. This works in a similar way to the actin and myosin filaments in muscles **Microtubules** - 7nm in diameter - Long and flexible - Can form mesh - They can aid movement by attaching to proteins called motor molecules. This works in a similar way to the actin and myosin filaments in muscles.   **Epithelial Tissues:** - Sheets of cells - Create boundaries (transport of ions) - Specialised cells: Enzymes, Milk, Mucus, Sweat Gut epithelial - High rate of division in skin - Cilia in gut. - Can provide information to CNS (taste, smell etc.) **Connective Tissues:** - Bone and Cartilage provide structural support - Blood a connective tissue situated within liquid extracellular matrix (plasma) - Adipose tissue or fat is a store of energy. It can protect organs and provide a barrier of heat loss within the skin. **Muscle Tissues**: - Skeletal muscle are primarily responsible for general movement. - Cardiac muscles are responsible for the beating of the heard and sending blood around the body. - Smooth muscle makes up the inner walls of some organs like the gut and bladder. **Neural Tissues**: - [Neurons] can vary, but all contain the ability to code and encode info. either produced or received. Neurons are the middleman between stimuli + response. - [Glial / glia cells] provide support + protection to neurons. They make barriers between the blood + nervous systems ensuring potentially harmful substances to not travel from the blood into the nervous system. **Homeostasis:** "A status of equilibrium where physical and biochemical processes can occur within a narrow range of different variables." **Phospholipids:** - Main structural unit of cell membrane - Organised in a bilayer - Three main structural units - Amphipathic **Cholesterol** - Steroid - Keeps membrane fluidity consistent - Amphipathic (hydrophobic and hydrophilic) - Prevents crystallisation **Glycolipids/proteins:** carbohydrate chain attached to lipid/protein - Glycolipid -- Attached to lipid - Glycoprotein -- Attached to protein - Important in cell recognition - Important in maintaining fluidity. **Integral proteins** - various forms + can often determine the specific function of that cell: 1. Channel Proteins 2. Carrier proteins 3. Cell recognition proteins 4. Receptor proteins 5. Enzymatic proteins  For a cell to function properly it must acquire many of these from the surrounding environment: - Semi-permeable Selectively permeable Some molecules may pass freely across the membrane, (small, noncharged molecules like CO2 or O2). Other molecules (larger or charged) need the support of carrier proteins. Molecules traveling across the membrane depends on the concentration gradient as some molecules must travel down a gradient or against the gradient.