Paper 1- Biology

• Cells:

  • All life consists of cells
  • Cells can be seen with a light microscope, but subcellular structures are visible with an electron microscope
  • Magnification is equal to image size divided by object size
  • Eukaryotic cells have a nucleus where DNA is found (e.g., plant and animal cells)
  • Prokaryotic cells do not have a nucleus and their DNA is found in a plasmid
  • Organelles in cells include the cell membrane, cell wall (in plants and most bacteria), cytoplasm, mitochondria, ribosomes, chloroplasts (in plant cells), and a permanent vacuole (in plant cells)
• • Bacteria multiply by binary fission
• Cell Division:

  • Eukaryotic cell nuclei contain DNA stored in chromosomes
  • Humans have 23 pairs of chromosomes in diploid cells
  • Gametes have half the number of chromosomes (haploid cells)
  • New cells are made for growth and repair through mitosis
  • Mitosis involves duplication of genetic material, doubling of ribosomes and mitochondria, breakdown of the nucleus, separation of chromosome pairs, and formation of two identical cells
• Stem Cells:

  • Stem cells are unspecialized cells found in human and animal embryos and the meristems of plants
  • Stem cells can be used to combat conditions like diabetes and paralysis
  • Cloning plants can prevent species extinction or produce crops with specific characteristics
• Diffusion and Osmosis:

  • Diffusion is the movement of molecules from high to low concentration
  • Osmosis is the diffusion of water across a semi-permeable membrane
  • Factors affecting diffusion rate include concentration difference, temperature, and surface area
  • Practical on osmosis involves using potato cylinders in sugar solutions
• Active Transport:

  • Active transport moves substances against a concentration gradient using energy
  • Enzymes are biological catalysts that break down larger molecules into smaller ones
  • Enzymes are specific and work on a lock and key principle
  • Enzyme activity increases with temperature up to an optimum point
  • Food tests can identify nutrients like starch, sugars, proteins, and lipids
• Respiratory System:

  • Breathing provides oxygen for cellular respiration
  • Air moves through the trachea, bronchi, bronchioles, and alveoli for gas exchange
  • Oxygen binds to hemoglobin in red blood cells for transport
  • Carbon dioxide is exhaled during respiration
• Circulatory System:

  • The heart is part of the double circulatory system
  • Blood enters the heart twice, once from the body and once from the lungs
  • Arteries carry oxygenated blood away from the heart, veins carry deoxygenated blood towards the heart
  • Arteries have thicker walls and veins have valves to prevent backflow
  • Capillaries have one-cell thick walls for fast diffusion
  • The coronary artery supplies the heart muscle with oxygenated blood
• The heart is a muscle that needs its own supply of oxygen and blood to keep pumping
• The coronary artery delivers oxygenated blood to the heart muscle
• Blockage of the coronary artery by fatty deposits can lead to a heart attack, known as coronary heart disease (CHD)
• Stents are inserted into blood vessels to keep them open for proper blood flow
• Statins are drugs that reduce cholesterol levels, which helps reduce fatty deposits in blood vessels
• Faulty heart valves can cause backflow, which can be replaced with artificial valves
• Blood carries red blood cells, white blood cells, and platelets
• White blood cells combat infections
• Platelets clump together to clot wounds and stop bleeding
• Cardiovascular disease (CVD) is a non-communicable disease
• Non-communicable diseases are caused by factors within the body, such as obesity, high sugar intake, smoking, and lack of exercise
• Type 2 diabetes can be caused by obesity and high sugar intake
• Alcohol consumption can lead to liver diseases
• Smoking can cause lung disease or cancer
• Carcinogens increase the risk of cancer
• Cancer is the result of damaged cells dividing uncontrollably, leading to tumor formation
• Plants have organs like leaves where photosynthesis occurs
• Water and mineral ions enter plants through roots
• Xylem are long tubes that transport water in plants
• Phloem transport sugars and sap in plants
• Transpiration is the process of water evaporating from leaves
• Nitrate ions are essential for protein synthesis in plants
• Chlorosis is the yellowing of leaves due to magnesium deficiency
• A leaf's structure includes the cuticle, upper epidermis, palisade mesophyll, spongy mesophyll, vascular bundle, and lower epidermis
• Infection and response involve pathogens like viruses, bacteria, fungi, and protists
• Skin is the first barrier against pathogens
• White blood cells, like lymphocytes, combat pathogens by producing antibodies and antitoxins
• Vaccines expose the immune system to pathogens to produce antibodies without causing infection
• Antibiotics kill bacteria, not viruses
• Monoclonal antibodies are specific antibodies produced to combat diseases
• Bioenergetics involves photosynthesis and respiration in plants and organisms
• Photosynthesis produces glucose for energy and other compounds like starch, fat, cellulose, and amino acids