(NHHS) Pure Biology Notes/Summary

guan studies 🤓 CELL STRUCTURE AND ORGANISATION term definition cell a unit of life that consists of living matter called protoplasm differentiation the process by which a cell becomes specialised for a specific function 🧠 protoplasm of a cell is made up of: cell surface membrane, cytoplasm and nucleus light microscope electron microscope magnifies up to 1000x magnifies up to 200000x colour images black and white images organelle characteristics cell surface membrane ● it is partially permeable ● it controls the movement of substances in and out of the cell cell wall ● made of cellulose ● it protects the cell from injuries and gives the cell a regular shape ● it is fully permeable cytoplasm ● site where most cell activities and chemical reactions occur nucleus ● controls all cell activities within the cell ● consists of a small round denser protoplasm called nucleoplasm which is surrounded by a nuclear envelope ● it may contain one or more nucleoli and chromatin chromatin ● chromatin is a network of threadlike structures that controls cell activities like cell division. ● it is made up of deoxyribonucleic acid or DNA which carries hereditary information. ● chromatin threads condense into chromosomes when the cell is dividing

rough endoplasmic reticulum ● the RER appears rough because small particles called ribosomes are attached to its outer surface ● ribosomes are required to make proteins ● the RER transports proteins to the golgi apparatus for secretion out of the cell *ribosomes can also be found freely in the cytoplasm. they synthesise proteins which are used within the cell smooth endoplasmic reticulum ● the SER is more tubular and does not have ribosomes ● it synthesises substances such as fats and steroids ● it is involved in detoxification golgi apparatus ● consists of flattened spaces surrounded by membranes ● chemically M odifies substances produced by ribosomes on the endoplasmic reticulum ● S tores and P ackages (MSP) the substances in vesicles for secretion out of the cell ● looks like wifi on diagrams mitochondia ● mitochondrion (singular) is a site for aerobic respiration where glucose is oxidised in the presence of oxygen to release ( ❌ produce) energy for cellular activities (enzymes are involved) chemical equation : glucose + oxygen → carbon dioxide + water + large amount of energy chloroplasts ● oval structures containing pigment chlorophyll which is required for photosynthesis to occur vacuoles ● store substances within the cell describe how proteins made in the cell are released to the outside of the cell. [3] ● proteins are synthesised by the ribosomes and sent via vesicles on the rough endoplasmic reticulum (RER) to the golgi body ● here, they are chemically modified, sorted and packaged into vesicles that pinch off the golgi body ● the secretory vesicles move to and fuse with the plasma membrane to release the proteins outside the cell plant cell animal cell cell wall present cell wall absent presence of a large, central sap-filled vacuole presence of many small and temporary

vacuoles chloroplasts present chloroplasts absent cell structure adaptation to function red blood cell ● contains haemoglobin which binds to oxygen and transports it around the body ● has a circular, biconcave shape which increases the surface area to volume ratio so that oxygen can diffuse in and out at a higher rate ● lacks a nucleus, enabling the cell to store more haemoglobin for transport of oxygen ● is flexible so it can squeeze through tiny capillaries easily ● can become bell-shaped in capillaries, further increasing surface area to volume ratio muscle cell ● is elongated and cylindrical in shape, contains many nuclei and mitochondria ● has mitochondria to provide the energy for the contraction of the muscle cell root hair cell ● has a long and narrow root hair to increase the surface area to volume ratio to absorb water and dissolved mineral salts at a higher rate ● has a large central vacuole to increase concentration of salt and sugars in the cell sap which lowers the water potential so that a steeper gradient is set up for faster absorption of water via osmosis ● have many mitochondria to generate a lot of energy via aerobic respiration for active transport to absorb mineral salts

MOVEMENT OF SUBSTANCES term definition concentration gradient the difference in concentration between two regions diffusion the net movement of particles from a region of higher concentration to a region of lower concentration, down a concentration gradient osmosis the net movement of water molecules from a region of higher water potential to a region of lower water potential, down a water potential gradient through a partially permeable membrane answer format : 1. compare water potential 2. net movement of water from … to … by osmosis down a water potential gradient through a partially permeable membrane 3. effects active transport the process in which energy is used to move the particles of a substance across a membrane against its concentration gradient, that is, from a region of lower concentration to a region of higher concentration *requires a partially permeable membrane 🧠 factors that affect rate of diffusion: 1. concentration gradient ○ steeper concentration gradient = faster rate of diffusion 2. diffusion distance ○ shorter diffusion distance = faster rate of diffusion 3. surface area to volume ratio ○ greater surface area to volume ratio = faster rate of diffusion 🌱 plant cells placed in solutions with higher / lower water potential ● the solution has a higher / lower water potential as compared to the plant cell’s cell sap ● there will be a net movement of water molecules from the solution to the plant cell’s cell sap / plant cell’s cell sap to the solution ● down a water potential gradient, through a partially permeable cell membrane, by osmosis ● plant cell more turgid and firm / becomes flaccid and plasmolysed ● cell membrane and cytoplasm pull away from the cell wall 🐹 animal cells placed in soluti