Life Science Tests: Exam Prep

• Resource pack aims to help grasp key concepts, establish required standards, and apply knowledge for success in work and assessments
• The resource pack covers scientific skills, the chemistry of life, cells as basic units, and mitosis

Examination/Test Writing Tips

• Answer all questions
• Number answers correctly
• Follow question instructions
• Use pencil for drawings
• Label drawings in blue or black ink
• Only draw diagrams, tables, or flow charts if asked
• Note that diagrams in question papers are not to scale
• Do not use graph paper for graphs
• Use a non-programmable calculator, protractor, and compass if needed
• Write neatly and legibly
• Use correct biological terminology and scientific names, avoiding common names
• Instruction verbs and mark allocation indicate the amount of information needed

Life Science Tests

• Life Science tests and exams have two sections: A and B
• Answer multiple-choice questions by carefully reading all options and eliminating incorrect ones

Instructional Verbs

• Name: Give the name of something
• Differentiate: Use differences to qualify between two or more categories
• Tabulate: Draw a table and give answers as direct pairs
• Describe: State the main points in sentences in a process
• Explain: Give cause-effect or statement-reason sequence answers

Scientific Skills

• Calculations will involve addition, subtraction, multiplication, and division
• Use a calculator
• Show calculation steps for marks
• Include the unit in the final answer

Data Presentation

• Scientific data is presented in tables or graphs

Tables

• Tables record results of investigations, require headings, and have rows/columns
• Label each column and row with applicable units
• Rows run from left to right
• Columns are vertical blocks
• Independent variables are in the left-hand column, dependent in the right

Graph Types

• Use line graphs to show the relationship between two types of information where the independent variable is continuous, to track trends over time, often used for biological data
• Bar graphs illustrate different data categories comparing values across categories, used when the independent variable consists of discontinuous data
• Histograms display connected bars to show continuous data, values of independent variables are continuous and fit into categories/groups following each other
• Pie charts are circular charts used to compare parts of the whole and are divided into sectors representing quantities, useful for discontinuous data

Scientific Investigations

• Questions are text and data-rich, where the stem and the investigative process should be carefully read
• Observation: Scientists saw, heard, or encountered an event that encouraged further investigation
• Hypothesis: A possible prediction and/or explanation of the relationship between two variables
• Aim: starts with the words "to investigate…" and includes both variables and describes the purpose of an investigation
• The independent (manipulated) variable: is the variable the scientist manipulates/controls shown on the X-axis
• The dependent (responding) variable: reacts/responds to the independent variable on the Y-axis
• Controlled variables: These must be kept constant to ensure an investigation's validity, ensures only the independent variable impacts any effect
• The control: sets up a second similar investigation, it excludes the variable being tested, compares against the experiment
• Accuracy: refers to the care taken when making measurements
• Validity: covers appropriateness of experiment method and how appropriate it is, it should address the aim of the investigation, identifying controlled variables helps the validity
• Results: the evidence produced during an investigation which either support or refute the hypothesis, presented in the form of an extract, a table, a graph or a diagram
• Reliability increases if the investigation is repeated, a bigger sample size is used, random samples are taken as well as multiple readings to obtain an average
• Conclusions link to the aims of the investigation so that it confirms or refutes the hypothesis

Hypothesis Formulation

• The hypothesis must have two variables: dependent AND independent
• It must state the relationship, be testable, and include the indepedent variable first, then the dependent (cause and effect)

Chemistry of Life

• Organic molecules consist of carbon (C), hydrogen (H), and oxygen (O), with some containing nitrogen (N) and phosphorus (P)
• Cells are made up of proteins, carbohydrates, lipids, nucleic acids, and vitamins

Inorganic Compounds

• Do not contain carbon or organic matter, produced by living organisms such as water, gases and minerals

Water

• The most important inorganic compound and is essential for life
• One oxygen (1 O) atom bonded to 2 hydrogen (2 H) atoms, chemical formular H2O

Minerals

• Divided into two groups, being micro and marco elements
• Marco elements are nutrients needed in large quantities
• Micro elements are nutrients needed in small quantities

Macro Elements

• Sodium (Na) maintains water balance and nerve/muscle function
• Muscular cramps are a deficiency disease
• Potassium (K) is required for nerve/muscle function and activates plant enzymes, and it's deficiencies are poor heart/muscle function or chlorosis in plants
• Calcium (Ca) is required for bone/teeth formation and its deficiency is rickets/poor root growth in plants
• Phosphorus (P) is needed for bone/teeth formation and its deficiency is rickets and stunted growth Component of cell membranes, nucleic acids

Micro Elements

• Iron (Fe) synthesizes hemoglobin and chlorophyll
• Anemia and chlorosis are deficiency diseases of Iron
• Iodine (I) is a hormone that regulates thyroxin excretion
• Goitre (swelling of the neck or larynx) in the thyroid gland is a deficiency diseases of Iodine

Carbohydrates

• Carbohydrates composed of carbon (C), hydrogen (H), and oxygen (O), with a 2:1 ratio of hydrogen to oxygen atoms
• Saccharides are smaller units
• Monosaccharides: A type of single sugar such as, fructose, glucose, or galactose
• Disaccharides: Is a double sugars such as maltose, sucrose, and lactose
• Polysaccharides: Many sugars, long chains of monosaccharides, such as starch, glycogen and cellulose

Testing for Carbohydrates

• Benedict solution (blue liquid) test tests for glucose
• Iodine solution (brown liquid) tests for starch

Lipids (Fats and Oils)

• Contain carbon (C), hydrogen (H), and oxygen (O), but the ratio of H to O is greater than 2:1
• One molecule contains one glycerol and three fatty acid molecules
• Saturated fats: Are mainly single bonds derived from animals, solids at room temp (butter, cheese)
• Unsaturated fats: Have one or more double bonds derived from plants, liquids at room temp (olive oil/canola/sunflower)

Cholesterol and Heart Disease

• Cholesterol is a lipid, wax-like substance in cell membranes
• Excessive saturated fats lead to high blood cholesterol levels
• High cholesterol causes fatty deposits in arteries
• Narrows arteries that interfere with blood transport
• Can lead to heart attack

Test for Fats

• Grind the test material (peanuts),
• Then place into test tube, adding 5cm3 of the ether or ethanol
• Shake and stand for a few minutes, where the filtrate is put on clean filter paper
• The ether/ethanol evaporates, where translucent fatty stain will appear

Proteins

• Proteins are polymers made of carbon (C), hydrogen (H), oxygen (O), and nitrogen (N).
• Proteins contain phosphorous (P), sulphur (S), and iron (Fe)
• Amino acids (the building blocks), make long chains
• Sequence/type determines the protein
• Peptide bond: A bond that forms between two amino acids

Dipeptides

• Formed when two amino acids combine, where a tripeptide forms when three combine
• Polypeptide: A long chain of amino acids linked by peptide bonds
• A protein consists of a chain of at least 50+ amino acids

Protein Sensitivity

• Proteins are sensitive to temp/pH
• Denature with high temperatures and extreme pH levels, loses shape/function

Proteins Test

• Biuret test is used to test for the presence of proteins
• Grind food, add water, and boil to create soup
• Add copper sulfate solution to a test tube, 5cm3 of soup
• Shake test tube, heat mixture, where violet color indicated the presence of proteins

Enzymes

• Chemical reactions taking place in cells known as metabolic reactions
• Are proteins biological catalysts
• Speeds reactions, not being used up in the reaction itself

Metabolic Reactions

• Enzymes reactions can be catabolic and anabolic
• Anabolic: Reactions of a complex molecule being built from simpler ones
• Catabolic: Reactions that break down complex into simple molecules
• Digestion of food, complex molecules are broken down with enzymes

Enzyme Action (Lock and Key Model)

• Substrate: A substance an enzyme reacts on
• Product: A reaction that occurs as the substance formed
• Enzyme is specific to a substrate e.g. sucrase will only react with sucrose
• The substrate fits into the active site of the enzyme, acting like a key fitting into a lock
• Enzyme-substrate complex is formed
• Substrate becomes product after the reaction, now leaving enzyme
• Now that the enzyme is free, it can react with other substrate molecules

Enzyme Activity

• Enzymes are sensitive to changes in temperature, most are inactive at low temperatures
• Optimum temperature: The temp at which the enzyme works the best (35-40 ºC)
• Enzymes denature their shape/function and denature at higher temperatures

Enzymes in Everyday Life

• Washing powders are biological, such as lipase and protease, for stain removal
• The protease enzyme can removes protein stains by breaking down stains into smaller molecules

Nucleic Acids

• Made up of the elements carbon (C), hydrogen (H), oxygen (O), nitrogen (N) and phosphorus (P)
• Includes DNA (deoxyribonucleic acid) and RNA (ribonucleic acid)
• DNA: Found in the nucleus and carries hereditary characteristics
• RNA: Found in nucleus and cytoplasm, and its used in protein synthesis

Vitamins

• They are organic compounds required in small quantities by animals
• Are essential for metabolism, growth, and development

Vitamins Sources/Deficiency Diseases

• Vitamin A: Yellow vegetables and liver, where Night-blindness is its deficiency
• Vitamin B1: Brown rice, wholegrain bread, legumes, with Beri-beri deficiency
• Vitamin C: Citrus fruit and tomatoes. Scurvy its deficiency
• Vitamin D: Oily fish and milk, its deficiency can result in Rickets
• Vitamin E: Spinach, lettuce, its deficiency can result in Poor nerve conduction, anemia

Cells

• The basic unit of all life
• Has a cell structure and function made up of organelles

Cell Wall

• Rigid, non-living layer on outside that surrounds cell membrane
• Consists of cellulose and is on exterior of cell membrane
• Only occurs in plants

Cell Wall Functions

• Is the support structure to protect living contents
• Gives rigidity
• Completely permeable for water and mineral salts

Cell Membrane

• Forms the outer living boundary of the cytoplasm
• All plant and animal cells have one
• Cell membrane make-up is on double phospholipid molecules with large embedded protein molecules

Membrane Function

• Selectively permeable
• Controls substance movement
• Diffusion is a spontaneous movement of molecules (liquid or gas)
• Goes from high to low concentration
• Its a passive process with no use of energy

Osmosis:

• Movement of from high to low water potential through a selectively permeable membrane
• Passive and uses no energy
• Plants extract water and transports it to the leaves via osmosis

Active Transport

• Moves molecules from low to high concentration through membranes
• Requires energy transfer in the process

Nucleus Components

• Double membrane, pores, nucleoplasm, nucleolus, chromatin network, with pores
• Chromatin networks shorten/thicken into chromosomes when cell divides

Nucleus Function

• Is what controls cell's activities
• Chromosomes carry hereditary characteristics

Cytoplasm Elements

• Semi-liquid base and jelly-like base states
• Dissolved nutrients and waste
• All organelles except the nucleolus are held

Cytoplasm Functions

• Stores substances
• Substances circulate with movement of cytoplasm

Mitochondria Qualities

• Can occur in animals or plants in their cytoplasm
• Cylindrically shaped and enclosed by a double membrane with folds called cristae
• Cristae increase inner surface increasing volume of chemical reactions that can take place in/filled with the semi-fluid substance, the matrix

Mitochondria Function

• Releases energy during cellular respiration

Ribosome Characteristics

• Small round structures can be found in either animal/plant cells
• Single in cytoplasm, either in groups or attached to endoplasmic reticulum
• Consists of RNA/proteins

Ribosomes Function

• Site of protein synthesis

Endoplasmic Reticulum (ER) Description

• Membranous network can be found in plant/animal cells
• Smooth & Rough ER types
• Rough if there are ribosomes on it

ER Functions

• Transports substances from one cytoplasm part to another

Golgi Body

• Stacks of flat membrane-bound cisternae
• Found close to endoplasmic reticulum or nucleus
• Can be in both animal and plant cells

Golgi Function

• Is both an organelle for secretions and produces mucus/saliva
• Stores proteins for transport

Plastids

• Only in plant cells
• Includes chloroplasts, chromoplasts, and leucoplasts

Chloroplasts

• Found mainly in leaves (areas of photosynthesis)
• Double membrane, filled with stroma
• In it are disc-shaped thylakoids/lamellae
• Stacks are "grana"
• Is where chorophyll is

Chromoplasts

• Yellow, red, and orange in leaves and fruit
• Contain carotenoids

Leucoplasts

• Colourless
• Store plastids in parts such as potatoes

Plastid Functions

• Have the process of photosynthesis
• Provides specific colors of yellow, red, orange in the flowers, leaves and fruit
• Store food

Vacuoles

• Fluid-filled organelles occurring in cytoplasm of most plant cells
• Small and absent in animal cells
• Has tonoplast to enclose selectively permeable parts
• Are filled with cell sap for mineral content, sugars and amino acids

Vacuole Functions

• Important in waste digestion/excretion storage and role in cellular waste, storing water, and storing inorganics and organics
• Responds to surrounding water intake changes
• Maintains water shape, cell exerts outwards pressure that pushes cell membrane in a process called turgor

Other Types of Vacuoles

• Vesicles: Small, spherical sacs that transport and store
• Lysomes: Small vesicles in animal cells with digestion enzymes that digest food

Animals VS Plants

Cell Division (Mitosis)

• The cell cycle refers to when the cell grows
• The process replicated genetics and divides during cells
• Interphase is the time between cell divisions
• DNA replication and the cell grows Two chromatids formed together make a centromere

Prophase

• Chromatin network shortens, forms individual chromosomes
• Each chromosome consists of 2 chromatids joined by a centromere
• Nuclear membrane/nucleolus vanish
• Centrioles separate
• Move to opposite poles
• Spindle fibers form between centrioles

Metaphase

• Chromosomes move to equator aligned in single row
• Each chromosome attaches to the spindle fibre by centromere

Anaphase

• Centromere divides chromosome into two
• Chromatids separate
• Spindle fibre contracts pulling chromatids to opposite poles
• Chromatids move to these opposite poles

Telophase

• Called chromosomes again, chromatids become chromosomes arranging at the cell poles themselves
• Spindle fibres disappear
• Nuclear membranes around chromosomes reappears
• Cytoplasm divides in cytokinesis

Mitosis's Role

• It increases cell numbers, allows development from a single cell, by facilitating organisms to grow from it
• Some organisms use to produce clones and identical offspring with genetics
• The cell parts such as skin are cells with cell replacement qualities
• Damaged tissues are able to be replaced by performing mitosis