Combined Science Biology Paper 1

• Electron microscopes have a better resolving power and a higher resolution
• The magnification of a microscope is equal to the image size divided by the object size.
• Prokaryotic cells contain a nucleus

  False
• Match the cell structure with its function:

  Cell membrane ↔️ Controls what enters and exits

  Mitochondria ↔️ Releases energy through respiration

  Ribosomes ↔️ Synthesizes proteins

  Chloroplasts ↔️ Where photosynthesis takes place
• Plant cells contain a cell wall made of cellulose to provide a rigid structure.
• Bacteria multiply by a process called binary fission.
• Steps to prepare a bacterial culture using aseptic technique:

  1️⃣ Lift the lid of the petri dish near a flame

  2️⃣ Use sterilized equipment to spread the bacterial culture

  3️⃣ Seal the dish with tape, leaving air gaps

  4️⃣ Incubate at 25 degrees Celsius
• Human diploid cells contain 23 pairs of chromosomes.
• Gametes are haploid cells, meaning they contain half the number of chromosomes as diploid cells
• Steps of mitosis:

  1️⃣ Genetic material is duplicated

  2️⃣ The nucleus breaks down

  3️⃣ Chromosomes are pulled to opposite sides

  4️⃣ A new nucleus forms in each side

  5️⃣ Two identical cells are formed
• Stem cells are found in human embryos and the meristem of plants.
• Stem cells in bone marrow can only specialize into blood cells
• Diffusion is the movement of molecules from an area of high to low concentration.
• Diffusion requires energy

  False
• Osmosis is the diffusion of water across a semi-permeable membrane.
• Steps to investigate osmosis in potato cylinders:

  1️⃣ Cut equal-sized potato cylinders

  2️⃣ Weigh the cylinders

  3️⃣ Place in test tubes with sugar solutions of varying concentrations

  4️⃣ After a day, reweigh the cylinders

  5️⃣ Calculate the percentage change in mass

  6️⃣ Plot the results on a graph
• Active transport moves substances against the concentration gradient
• Match the type of protein with its function:

  Carrier protein ↔️ Moves substances across a membrane

  Enzyme ↔️ Biological catalyst

  Structural protein ↔️ Provides cell shape and support

  Hormone ↔️ Chemical messenger
• A group of similar cells working together forms a tissue.
• Organs work together in an organ system
• Bile emulsifies fats, increasing their surface area for enzymes to break them down.
• Enzymes are specific because they work on a lock and key principle
• The rate of enzyme activity increases with temperature until it reaches its optimum temperature.
• Steps to investigate enzyme activity using amalayise:

  1️⃣ Mix amalayise with starch at different temperatures

  2️⃣ Every 10 seconds, add drops to iodine

  3️⃣ Record the time taken for starch to break down

  4️⃣ Calculate the rate of reaction
• Match the food test with its result:

  Iodine ↔️ Turns black in the presence of starch

  Benedict's solution ↔️ Turns orange in the presence of sugar

  Biuret reagent ↔️ Turns purple in the presence of protein

  Cold ethanol ↔️ Turns cloudy in the presence of lipids
• The respiratory system includes the trachea, bronchi, bronchioles, and alveoli.
• Alveoli have a large surface area due to their lumpy structure
• Oxygen in the blood binds to hemoglobin in red blood cells.
• Carbon dioxide is transported in the plasma of the blood
• The circulatory system is a double circulatory system because blood passes through the heart twice every cycle.
• Steps of blood flow through the heart:

  1️⃣ Deoxygenated blood enters the right atrium

  2️⃣ Passes to the right ventricle

  3️⃣ Sent to the lungs through the pulmonary artery

  4️⃣ Oxygenated blood returns to the left atrium

  5️⃣ Passes to the left ventricle

  6️⃣ Pumped to the body through the aorta
• Arteries carry oxygenated blood except for the pulmonary artery
• Arteries have thicker walls to withstand higher pressure.
• Veins have valves to prevent backflow of blood
• Match the blood vessel with its characteristic:

  Artery ↔️ Thick walls, high pressure

  Vein ↔️ Thin walls, valves

  Capillary ↔️ One cell thick, diffusion
• The coronary artery provides the heart muscle with its own oxygen supply.
• Statins are drugs that reduce cholesterol and fatty deposits
• Faulty heart valves can be replaced with artificial ones.
• Match the blood component with its function:

  Red blood cells ↔️ Carry oxygen

  White blood cells ↔️ Combat infections

  Platelets ↔️ Clot blood

  Plasma ↔️ Transports substances
• Communicable diseases are caused by pathogens