Lernziele Test 2 PDF

# Lernziele Test 2 ## Biomembrane: - Cells and cell organelles have membranes to allow undisturbed chemical reactions and metabolism (compartmentalization). - Membranes consist of a double layer of phospholipids. - Phospholipids organize themselves in aqueous solutions. - Different substances hav...

# Lernziele Test 2 ## Biomembrane: - Cells and cell organelles have membranes to allow undisturbed chemical reactions and metabolism (compartmentalization). - Membranes consist of a double layer of phospholipids. - Phospholipids organize themselves in aqueous solutions. - Different substances have different properties and therefore don't mix (water and fat). - Phospholipids are situated between the water and fat layers. - The fat-loving (lipophilic) parts are arranged towards each other to avoid contact with water. - The water-loving (hydrophilic) parts are facing the water. - Hydrophilic parts attract each other and so do lipophilic parts. - Membranes are impermeable to molecules except H2O, CO2, and O2. ### Particle Movement and Diffusion - Substances exist in different states of matter. - In liquid and gaseous state, particles move. - They collide with each other, meaning that their direction and speed are constantly changing (not measurable). - In a warm state, they move quicker, which means that they mix quicker. - This is diffusion (substance is equally distributed/mixed without stirring). ### Osmosis - Water always moves to the side with the higher concentration of dissolved substances (salt, sugar). - If the cell has more dissolved substances (hypertonic solution), the cell shrinks because it loses water. - If the cell has fewer dissolved substances inside (hypotonic solution), it swells up because water flows into it. - Plant cells cannot burst because they have a cell wall, while animal cells can because they don’t have a cell wall. - Plants are stable if the water inside pushes against the cell wall, but they become limp if they lose water. - Living beings wouldn't be able to survive if there is a high concentration of a substance because osmosis would constantly lead to water loss. - The salt concentration of humans is 9g salt per liter. - Drinking saltwater is not good because we lose a lot of water (drinking in the sea). - Drinking a lot of pure water is also not good because it hardly contains dissolved substances and therefore uncontrollably enters the cells and our tissue swells up until the cells burst. - There are drinks with the same concentration of dissolved substances as our body, so we don't lose large amounts of water. ### Transport in Biomembranes - If a membrane only lets small things through like H2O, CO2, O2, it is semipermeable. - if it lets a little more through, it is selectively permeable. - Membranes still need to transport larger molecules. - Therefore, there are carrier and channel proteins. - Diffusion is passive transport and is too slow (independent). - In simple diffusion, small things can just cross the membrane, but in facilitated diffusion, channel proteins help to transport larger substances. - Active transport needs quite a lot of energy (forced energy). - Secondary active transport needs a primary one as energy. - Primary active transport uses the energy of ATP and transport proteins. - Channel proteins are channels for certain substances and carriers (active/passive) are proteins that bind substances on one side of the membrane. - The concentration gradient is the concentration difference between two sides of the membrane. ## Cell Organelles: - **Cell nucleus:** control (chromatin framework genetic information) - **Vacuole:** waste - **Chloroplasts:** photosynthesis (H2O + CO2 + light → Glucose + O2) - **Mitochondria:** cell respiration (glucose is burnt, using up O2 → ATP) - **Ribosomes:** small bodies that read the mRNA molecules that flow out of the nuclear pores and translate the code to build proteins. - mRNA has the sequence of 20 amino acids. - The amino acid arrives at the back of the ribosome, folds into a protein. - free in cytoplasm - attached to ER chains - **Endoplasmatic reticulum:** membrane system that connects to the nuclear membrane - Rough ER: has ribosomes, many proteins, membrane connection to Golgi apparatus - Smooth ER: performs metabolic processes and sometimes contains enzymes. - **Golgi apparatus:** takes up proteins and sorts them (location), then packages them into vesicles. - **Vesicles:** membrane bubbles that transport the proteins by splitting off to the target location. - There they merge with the membrane. - **Lysosomes:** large vesicles that digest dead cell material after the splitting from the Golgi apparatus. - Aggressive enzymes need to stay in lysosomes so they don't attack the cells. - **Cytoskeleton:** provides shape and stability with thick and thin proteins. - Transport takes place next to the fibers of the cytoskeleton. - Networks are created. ## Cell Differentiation: - In unicellular organisms, the cell is essential because all processes occur in it. - In organisms with multiple cells, these tasks/processes are divided. - **Tissue:** different cell types - **Organ:** different cell types perform one task together - **Organ system:** different organs perform one function. - **Organism:** living being - Cells differentiate after receiving a signal from the outside, by recognizing which parts of the genetic information they need to activate. - **Permanent tissue:** not dividable, large vacuoles, large size - **Body stem cells:** cell renewal, differentiation - **Embryonic stem cells:** self-renewal, rapid multiplication ## Mitosis: - Mitosis is the process in which one chromosome with a double chromosome set is turned into two chromosomes with a double chromosome set. - Humans have 23 pairs of chromosomes, with one coming from the father and one from the mother. - We have a double chromosome set where we always have two versions, which are very similar to the chromosome. - Before cell division, the chromosomes are chaotic threads in the nucleus. - **Interphase:** genetic information is duplicated - **Prophase**: chromosomes wrap themselves into 2 chromatid chromosomes. - **Prometaphase:** the nuclear membrane dissolves and the spindle fibers form (opposite to each other). - **Metaphase:** spindle fibers attach to the centromeres (hold the chromosomes together) and pull the chromosomes to the middle (equatorial plane) - **Anaphase:** the chromatids of each chromosome are separated by pulling of the spindle fibers. - **Telophase:** the chromatids reach one side, the spindle fibers dissolve and new nuclear membranes are formed. The chromosomes unwrap themselves again. - **Cytokinesis:** A new cell membrane (cell wall) is formed where the middle of the cell is. ## Enzymes: - Enzymes are proteins that enable metabolic processes/reactions to occur (catalyze). - They have a shape that allows the substance to be moved to fit in (active center). - Enzymes bind substrate (enzyme-substrate complex) and cause the substrate to be transformed into a different substance at 37°C. - Then the substance dissociates and the enzyme can take up new substrate. - Enzymes can also initiate reactions that are endothermic (need energy). They use ATP as energy for this. - **Catabolic enzymes:** decomposing enzymes that separate substrate into several products - **Anabolic enzymes:** building enzymes that make a product from two substrates.