Combined Science Final (IGCSE) Exam Questions And Already Passed Answers.
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Course
Combined Science
Institution
Combined Science
Movement - Answer An action by an organism causing a change of position or place.
Respiration definition - Answer The chemical reactions in cells that break down nutrient molecules and release energy.
Sensitivity - Answer The ability to detect and respond to changes in the environmen...
Combined Science Final (IGCSE) Exam
Questions And Already Passed Answers.
Movement - Answer An action by an organism causing a change of position or place.
Respiration definition - Answer The chemical reactions in cells that break down nutrient molecules and
release energy.
Sensitivity - Answer The ability to detect and respond to changes in the environment.
Growth - Answer A permanent increase in size.
Reproduction - Answer The processes that make more of the same kind of organism.
Excretion - Answer Removal from organisms of toxic materials and substances in excess of
requirements.
Nutrition - Answer Taking in of materials for energy, growth and development.
Plant cells - Answer Nucleus, cytoplasm, cell membrane, mitochondria, cell wall, chloroplasts, one big
vacuole.
Nucleus - Answer Its function is to control the actions of the cell, contains genetic material (DNA or
RNA).
Cytoplasm - Answer A place for chemical reactions to happen, it gives the cell its shape and keeps
organelles in place.
,Cell membrane - Answer Its function is to control the movement of substances in and out of the cell,
protective layer.
Mitochondria - Answer Cell part where respiration happens to produce energy.
Vacuole - Answer This is the storage of the cell, waste included.
Cell wall - Answer Its function is to keep the structure of the cell, it is located outside the cell
membrane.
Chloroplast - Answer Where photosynthesis takes place.
Ribosome - Answer Cell part where proteins are made.
Ciliated cells - Answer They have a hair-like structure to release mucus which helps to maximize the
surface area. Its function is movement of mucus in the trachea and bronchi.
Root hair cells - Answer The function is to absorb water and minerals. These cells are found in the roots
of plants and have a long finger-like projection, which increases their surface area.
Palisade mesophyll cells - Answer Function is to absorb light/ photosynthesis. They contain a high
number of chloroplasts and are located beneath the upper epidermis.
Red blood cells - Answer Function is to transport oxygen. The cell is flexible, lacks a nucleus and
contains haemoglobin.
Sperm and egg cells - Answer Function is reproduction. The head contains enzymes, the middle piece is
packed with mitochondria and has a tail to swim.
Small intestine cells - Answer Function is to absorb nutrients. Receives pancreatic secretions and bile
through the hepatopancreatic duct. They have microvilli to maximize the space.
,Nerve cells - Answer The nerve cells (neuron) function is to carry information throughout the body to
the brain. The neuron contains a nucleus that provides an environment for the transcription process and
contains the DNA from the cytoplasm. They have an axon so that the signal can travel faster.
Diffusion - Answer - The net movement of particles from a region of high concentration to a region of
low concentration, down a concentration gradient, as a result of their random movement.
- Substances move into and out of cells by diffusion, through a cell membrane.
- Examples: Gas exchange in the lungs and carbon dioxide in the leaf.
Osmosis - Answer - The net movement of water molecules from a region of high water potential (dilute
solution) to a region of low water potential (concentrated solution), through a partially permeable
membrane.
- Water diffuses through partially permeable membranes by osmosis.
- Water moves in and out of cells by osmosis through the cell membrane.
Percentage of change in mass = - Answer end mass - start mass (change in mass) / start mass
x 100
Magnification = - Answer size of image/ actual size of object
Macronutrients (need in large amounts): - Answer Carbohydrates, Proteins and Fats.
Micronutrients (need in small amounts): - Answer Minerals, Water and Fibre.
Carbohydrates - Answer carbon, hydrogen, oxygen
Fats - Answer carbon, hydrogen, oxygen
Protein - Answer carbon, hydrogen, oxygen, nitrogen
, Starch and glycerol are made up of - Answer glucose
Proteins are made up of - Answer amino acids.
Fats and oils (lipids) are made up of - Answer fatty acids and glycerol.
An indicator is - Answer a substance that changes colour when a specific substance is added to the
sample and is present in the food we eat.
Test for simple sugars: Benedict's test - Answer - Benedict's solution is a blue indicator that changes
colour if glucose is present in a sample.
- The indicator will turn green (low amount), orange or red (large amount) depending on the amount of
sugar in the sample.
To test if it is there in the food, you first add the solution to a test tube then heat it in a warm water bath.
You then add the solution to the food and see what colour it turns.
Test for proteins: Biuret test - Answer - Biuret solution is a blue liquid that turns purple when proteins
are present in a sample.
To test this, you would add a few drops of biuret reagent, shake the solution in a test tube, then add it to
the food and see if it turns purple.
Test for Starch: Iodine test - Answer Iodine is a brown liquid that changes to blue/dark blue when
starch is present in a sample. To test this you would add a few drops of iodine reagent to the food.
Test for fats: Emulsion (Ethanol) test - Answer Ethanol 95% is colourless alcohol that can dissolve fats in
a sample, forming a white emulsion. To test this you would add ethanol to the food to dissolve the fat,
then add distilled water.
Enzymes - Answer Are proteins that function as biological catalysts. They ensure that the rates of
metabolic reactions are great enough to sustain life.
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