Structure and functions of living organisms(biology)

• Cell structure:

  • Organelles are specialised subcellular structures found within living cells
  • Cells are the basic structural unit of a living organism
  • Tissues are groups of cells with similar structures, working together to perform the same function
  • Organs are groups of tissues working together to perform specific functions
  • Organ systems are groups of organs with similar functions, working together to perform body functions
  • An example of an organ system is the respiratory system, containing the lungs (organ), made up of epithelial tissue consisting of epithelial cells
• Subcellular structures found in plant and animal cells:

  • Nucleus:
  • Contains the genetic material that codes for a particular protein
  • Enclosed in a nuclear membrane
  • Cytoplasm:
  • Liquid substance where chemical reactions occur
  • Contains enzymes that speed up the rate of reaction
  • Cell membrane:
  • Contains receptor molecules to identify and control what enters and leaves the cell
  • Mitochondria:
  • Where aerobic respiration reactions occur, providing energy for the cell
  • Ribosomes:
  • Where protein synthesis occurs and found on the rough endoplasmic reticulum
• Subcellular structures found only in plants:

  • Chloroplasts:
  • Where photosynthesis takes place, providing food for the plant
  • Contains chlorophyll pigment that harvests light for photosynthesis
  • Permanent vacuole:
  • Contains cell sap and improves cell rigidity
  • Cell wall:
  • Made from cellulose and provides strength to the cell
• Specialised cells:

  • Specialised cells develop certain characteristics to perform specific functions
  • Cells specialise through differentiation, gaining new sub-cellular structures for their role
  • Stem cells can differentiate once early on or throughout their life
  • Examples of specialised cells in animals:
  • Sperm cells, Nerve cells, Muscle cells
  • Examples of specialised cells in plants:
  • Root hair cells, Xylem cells, Phloem cells
• Stem cells in medicine:

  • Characteristics: undifferentiated cells that can divide to produce different cells
  • Types: Embryonic stem cells, Adult stem cells, Meristems in plants
  • Uses: development, growth, repair
  • Potential applications in treating diseases and conditions
• Biological molecules:

  • Carbohydrates: made of carbon, oxygen, and hydrogen, break down into simple sugars
  • Proteins: made of carbon, oxygen, hydrogen, sulfur, nitrogen, and phosphorous, break down into amino acids
  • Lipids: fats and oils made of carbon, oxygen, and hydrogen, break down into 3 fatty acids and a glycerol molecule
• Enzymes:

  • Enzymes are biological catalysts, protein molecules with a specific active site
  • Lock and Key Hypothesis explains enzyme-substrate interaction
  • Factors affecting enzyme activity: temperature and pH
  • Practical investigations on enzyme activity with changes in temperature and pH
• Practical on investigating food samples for glucose, starch, protein, and fat:

  • Tests for glucose, starch, protein, and fat with specific procedures and indicators
• To investigate the effect of pH on the reaction time of amylase breaking down starch:

  • Mix 3 cm3 of amylase solution, 2 cm3 of starch solution, and 1 cm3 of pH solution in a test tube
  • Place the test tube in a water beaker above a Bunsen Burn to maintain a constant temperature
  • Every 10 seconds, place a drop of the solution into iodine solution wells
  • The solution should turn blue-black when starch is present
  • Record the time taken for the solution to turn orange
• Repeat the experiment with different pH solutions
• Record results on a graph of pH (x-axis) and time taken for the reaction (y-axis)

  • The optimum pH for amylase is where the reaction is completed the fastest, likely around pH 7.0
• Diffusion:

  • Spreading of particles from an area of higher concentration to lower concentration
  • Passive process, no energy required
  • Small molecules like oxygen, glucose, amino acids, and water can diffuse, but larger molecules like starch and proteins cannot
• Examples of diffusion in living organisms:

  • Single-celled organisms use diffusion due to a large surface area to volume ratio
  • Multicellular organisms have adaptations for molecule transport, like alveoli in lungs, villi in intestines, and root hair cells in plants
• Factors affecting diffusion rate:

  • Concentration gradient: Greater difference leads to faster diffusion
  • Temperature: Higher temperature increases particle movement and collisions, speeding up diffusion
  • Surface area to volume ratio: Greater surface area allows faster diffusion
  • Distance: Longer distance increases diffusion time
• Osmosis:

  • Movement of water from a less concentrated to a more concentrated solution through a partially permeable membrane
  • Passive process, no energy required
• Examples of osmosis in living organisms:

  • Animals and plants experience osmosis effects based on external solution concentration
  • Osmosis in animals can cause bursting or shriveling of cells
  • Osmosis in plants affects turgor pressure and cell health
• Active transport:

  • Movement of particles from lower to higher concentration, against the gradient
  • Requires energy from respiration, hence called active
• Examples of active transport in living organisms:

  • Root hair cells uptake water and mineral ions from soil
  • Gut absorbs substances like glucose and amino acids into the bloodstream
• Leaf structures:

  • Waxy cuticle reduces water loss
  • Palisade mesophyll contains chloroplasts for photosynthesis
  • Spongy mesophyll has air spaces for gas exchange
  • Guard cells regulate stomata opening
  • Stomata allow gas exchange and water loss
• Mineral ions:

  • Magnesium is essential for chlorophyll production
  • Nitrate is needed for amino acid synthesis
• Nutrition in humans:

  • Balanced diet includes carbohydrates, proteins, lipids, dietary fiber, vitamins, minerals, and water
• Factors affecting energy requirements:

  • Age impacts energy needs
• Nutrients and their sources:

  • Iron: found in red meat, needed for haemoglobin, deficiency can cause anaemia
  • Water: found in water, juice, milk, needed for cell reactions to take place
• Factors affecting energy requirements:

  • Age:
  • Energy requirements generally increase as we approach adulthood
  • Energy needs of adults decrease as they age
  • Activity levels:
  • More activity requires more energy for movement
  • Pregnancy:
  • Energy requirements increase to support growth of the foetus
  • Energy needs increase due to the extra mass of the baby
• Human alimentary canal:

  • Mouth:
  • Mechanical digestion: teeth break up large food pieces into smaller pieces with larger surface area to volume ratio (food bolus)
  • Chemical digestion: amylase breaks down starch into glucose
  • Salivary glands produce saliva to lubricate the food bolus for easy swallowing
  • Oesophagus:
  • Tube from the mouth to the stomach
  • Food bolus moves down due to peristalsis created by circular and longitudinal muscles
• Pancreas:

  • Produces carbohydrase, protease, and lipase enzymes
  • Secretes enzymes into the stomach and small intestine
• Stomach:

  • Gastric juice is released when food is detected
  • Gastric juice contains pepsin (enzyme breaking down proteins) and hydrochloric acid
  • Peristalsis occurs in the stomach
  • Digested food is called chyme
• Small intestine:

  • Duodenum:
  • First part of the small intestine
  • Carbohydrases, proteases, and lipases digest food here
  • Bile is released into the duodenum to neutralize stomach acid and emulsify fats
  • Ileum:
  • Lined with villi for absorption of digested molecules into blood
• Large intestine:

  • Water absorption to produce faeces
  • Faeces stored in the rectum and removed through the anus
• Digestive enzymes:

  • Carbohydrates (starch): broken down by carbohydrases
  • Proteins: broken down by proteases
  • Lipids: broken down by lipases
• Respiration:

  • Occurs in every cell to supply ATP
  • Aerobic respiration uses oxygen and yields more energy
  • Anaerobic respiration occurs without enough oxygen and yields less energy
• Structure of thorax:

  • Ribs: bone 'cage' surrounding lungs for protection
  • Intercostal muscles: control inhalation and exhalation
  • Diaphragm: changes pressure for breathing
  • Trachea: windpipe for air entry to lungs
  • Alveoli: tiny air sacs for gas exchange
• Ventilation process:

  • Inhalation: intercostal muscles contract, ribcage moves up, diaphragm contracts downwards, pressure decreases, air moves in
  • Exhalation: intercostal muscles relax, ribcage moves down, diaphragm relaxes upwards, pressure increases, air moves out
• Alveoli adaptations:

  • Thin cell walls for shorter diffusion distance
  • Folded to increase surface area
  • Large network of capillaries for efficient gas exchange
• Transport:

  • Diffusion is the passive movement of particles from higher to lower concentration
  • Single-celled organisms rely on diffusion due to high surface area to volume ratio
  • Multicellular organisms have adaptations for efficient transport
• Transport in plants:

  • Phloem adaptations for translocation of sucrose and amino acids
  • Elongated cells with sieve plates for movement of food substances
• Companion cells have many mitochondria to provide energy for the cells
• Food substances can be moved in both directions (translocation) within plants
• Water travels up xylem from the roots into the leaves to replace lost water due to transpiration
• Xylem adaptations:

  • Lignin is deposited causing cells to die and become hollow, forming a continuous tube for water and mineral ions
  • Water molecules are attracted to each other by hydrogen bonding, creating a continuous column of water
  • Lignin strengthens the plant to withstand water pressure
  • Lignin contains bordered pits for water and mineral entry