VCE Biology Unit 1

Independent Variable

What you change or manipulate. (Only 1 Variable)

Dependent Variable

What you measure (give units) that is changed.

Controlled Variable

What remains the same in an effort to reduce the chance of influence on DV.

Uncontrolled Variable

What is not kept constant. (Extraneous variable) Eg. How evenly the E.coli is spread across an agar plate.

Experimental Group

 Group exposed to your IV. May be different levels of exposure (12 hrs, 36 hrs)

Control Group

Baseline comparison with experimental groups.

Negative Controls

Not exposed to any levels of IV.

Sometimes the negative control can be a placebo.

Positive Controls

Scientists apply a treatment which induces a well-understood effect on the DV.

Control Group ≠ Control Variable

Control Group ≠ Control Variable

Aim

• Purpose of investigation

• Make sure to use species name

• Start with: 1. To investigate 2. To determine if

Hypothesis

• A possible educated prediction that is a testable statement

• Describes how you think IV will affect DV including direction of change (increase/decrease)

• Either supported/non supported by results

Conclusion

• Restate purpose/aim and summarise data

• State if hypothesis was supported or unsupported

• What further evidence is required 

Risk Assessments

Identify, assess and control hazards, identify potential risks.

Quantitative Data

Data/variable that has a numerical value. Eg. 5cm

Continuous Variable

Results include decimal places. eg. Length, time, mass, temp

Discrete Variable

Whole number and not in parts. Eg. NUmber of bubbles, chromosomes, WBCs

Qualitative Data

Data/variable that has a description. Eg. Colour, smell, texture

Primary Data

Data collected by the person directly involved in the investigation.

Secondary Data

Data collected by someone else.

Accuracy

Close to the true value of the quantity being measured.

Precision

When two or more measurements are close to each other in value.

Outliers

A single data point that goes far outside the average value of a group of statistics.

Personal Error

• Human mistakes or miscalculations

• A type of random error

Random Error

• Unpredictable variations that affect precision.

• Can be observational or environmental.

• Eg. Weighing a moving insect on scales, reaction time with stopwatch, error in reading due to change in wind.

Effects of random error can be reduced by:

Making more repeated measurements and calculating a new mean by refining measurement method or technique.

Systematic Error

• Have a clear cause and can be eliminated

• Affect the accuracy of a measurement and cause readings to differ from true value consistently. Accuracy cannot be improved by repeating measurements.

Eg. A clock is 5 minutes slow, leaking gas cylinder, scales read 0.2g with nothing (calibration is wrong).

Repeatability

When scientists, using the methods they designed, can obtain the same result multiple times under the same conditions (people, equipment, laboratory).

Reproducibility

When a group of scientists, using methods designed by others, can obtain the same results as another group’s experiment under different conditions (different people, equipment, laboratory).

Improvements to Experimental Design

• Control group/placebo group

• Controlling more variables

• Repeating experiments and averaging results

• Increasing randomisation to reduce sample bias

• Blind: Recipient don’t know which treatment given, experimenter knows 

• Double Blind: Experimented and recipient don’t know which treatment given

Limitations to Experimental Design

• Size of sample group

• Range of IV is too small: 5c-25c

• Cost

• Availability of resources

• Time

• Ethical issues

Prokaryotic Cells

• Minimal defined internal structure

• No membrane-bound organelles

• Lack defined structure (nucleus) to house DNA

Prokaryotic Cell Examples

Bacteria, Archaea

Eukaryotic Cells

• Complex structure

• Many membrane bound structures

• Contain a nuclear envelope

• Some are unicellular, some multicellular

Eukaryotic Cell Examples

Animalia, Plantae, Fungi, Protista

Prokaryotic and Eukaryotic Cell Similarities

• Have chromosomes

• DNA

• Ribosomes

• Cytoplasm

• Plasma Membrane

• Vacuoles

Nucleus/Nucleolus

• Enclosed in nuclear envelope

• Contains genetic material

• Ribosome assembly

Cytoplasm/Cytosol

Cytosol is the fluid that organelles float in, and cytoplasm is the combination of cytosol and all organelles inside a cell.

Cell Membrane

• Made from phospholipid bilayer

• Controls movement of substances inside and outside of cell

• Outer surface of cells

Cell Wall

• Not membrane bound

• Strengthens, supports, protects

Ribosomes

• Not membrane bound

• Produces protein

• Attached to the rough endoplasmic reticulum

• Found in both prokaryotic and eukaryotic cells.

Smooth/Rough Endoplasmic Reticulum

• Transport and synthesizes proteins

• Smooth makes lipids

• Rough makes proteins and exports out of the cell

Golgi Apparatus

• Membrane bound

• Modifies and packages proteins

• Creates vesicles for exocytosis

Lysosomes

• Membrane bound vesicle

• Contains enzymes

• Destroy unwanted/damaged cell parts

Vacuoles

• Larger in plant cells

• Stores waters

• Creates turgor pressure, gives structure.

Mitochondria

• Produces energy, ATP

• Enclosed in double membrane

• Breaks down glucose to carbon dioxide and water to release energy

Chloroplasts

• Contains chlorophyll

• Traps sunlight to make glucose (photosynthesis)

• Double membrane

Vesicles

Transports proteins around the cell or to the outside of the cell.

Cytoskeleton

• Not membrane bound

• Backbone of the cell, allows movement and shapes

Cilia/Flagella

 Assists cell in movement. Tiny hairs or whip-like tail.

Plant Cell Vs Animal Cells

Plants:

• Cell wall

• Larger vacuoles

• Chloroplasts

• Lack centrosomes and lysosomes

Animal:

• No cell wall

• Smaller vacuoles

• No chloroplasts

• Has lysosomes and centrosomes

Surface Area to Volume Ratio

Comparison of the amount of SA (cell membrane) available for absorption and secretion of substances (oxygen and glucose), compared to the V (cytoplasm).

Surface Area to Volume Ratio Formula

Obtained by dividing an object's area by its volume.

Cell Size: SA:V Ratio

Smaller cell= SA:V increased, more efficient.

Bigger cell= SA:V decreased, less efficient

Methods to Overcome Size Challenges:

1. WBCs can grow more nuclei to supply enough proteins and RNA.

2. Some have lots of folds throughout the membrane. These can increase surface area.

3. Some cells can divide into two smaller cells.

4. RBC’s can lose organelles (nucleus included), to make more space for oxygen carrying haemoglobin. 

Biomolecules

• Polymers

• Organic molecules

4 Major Molecules

Proteins, Carbohydrates, Lipids and Nucleic Acid

Proteins

• Chains formed from the joining of monomers called amino acids.

• The joining of amino acids to form proteins occurs in the ribosomes.

• Each protein has a unique function and its own specific sequence/chain of amino acids.

Functions of Proteins

Enzymes to speed up reactions, antibodies in the immune response, assist with transport across cell membranes, carry oxygen in RBCs.

Carbohydrates

• Polymers (many monomers).

• The monomers of carbs (building blocks) are monosaccharide.

• An important source of energy.

Examples of Carbohydrates

Glucose, Lactose, Cellulose, Starch

Lipids

• Not true polymers

• Insoluble in water

• Made from fatty acids and glycerol

• Make up membranes and some human hormones eg. sex hormones

Nucleic Acid

• Main information carrying molecule in the cell.

• Two main classes: DNA and RNA.

• Made up of nucleotides (monomers) which contain a nitrogenous base, a phosphate and a sugar (ribose - RNA, deoxyribose - DNA)

Water

• Most abundant compound.

• Highly cohesive (attracted to each other) and adhesive (attracted to other things).

• Found in the blood, tissue fluid and lymph outside of cells.

• Also found in cytosol and organelles.

Plasma Membrane

• Semi-permeable barrier of the cell.

• All cells have one.

• Structure of the cell membrane is called the fluid mosaic model.

Fluid Mosaic Model

• Phospholipid bilayer with proteins embedded.

• Molecules that make up the membrane are not held static in one place.

• Fluid as the phospholipids that make up the membrane move laterally (side to side)

• It is a mosaic as it made up of more than one thing.

Phospholipids

• Hydrophobic tails, face away from water (Non-polar)

• Hydrophilic heads, face water solution (Polar)

Embedded Proteins

Peripheral: Attached to the surface or one side of the membrane

Transmembrane: Integral protein embedded in the membrane

Glycoproteins: Proteins with carbohydrates attached

Glycolipid: Proteins with lipids attached.

Glycoproteins and Glycolipids

Cellular recognition, Immune recognition

Cholesterol

Regulates fluidity in the cell.

Substances That Can Pass through the Membrane

• Lipid-soluble substances dissolve: Alcohol, Chloroform

• Tiny hydrophilic/polar molecules through osmosis: H20

• Small hydrophobic/non polar molecules: O2, CO2

Substances That Cannot Pass through the Membrane

• Medium sized hydrophilic substances: Ions, Amino acids

• Polar monomer molecules: Glucose

• Large molecules use bulk transport: Hormones and proteins

Passive Transport

Transport that takes no energy. The energy comes from the chemiosmotic potential due to the concentration gradient. 

Types of Passive Transport

1. Diffusion

2. Facilitated diffusion

3. Osmosis

Diffusion

The passive movement of particles from an area of higher concentration of a substance to lower concentration, in order to achieve equilibrium. If a solute can cross the semipermeable membrane, it will move to achieve the same concentration on both sides of the membrane.

Facilitated Diffusion

When charged particles or medium sized water soluble molecules (e.g. ions, glucose, amino acids) diffuse across a membrane through channel proteins or with the aid of carrier proteins. 

Osmosis

The passive NET movement of WATER across a semipermeable membrane along the concentration gradient.

When a solute (eg: salt, sugar, protein, etc.) cannot pass through a membrane but the solvent (water) can. Water always moves towards the more concentrated solution of solute, to make both inside and outside equal in dilution.

Isotonic

 Concentrations both inside and outside of the cell are the same.

Animal Cell Tonicity

Hypertonic: High solute, water leaves cell causing it to shrivel (crenation).

Hypotonic: Low solute, water enters the cell, causing it to swell, potentially burst (lysis).

Plant Cell Tonicity

Hypertonic: High solute, water leaves cell, cytoplasm shrinks, but cell wall maintains structured shape (plasmolysis/flaccid).

Hypotonic: Low solute, water enters the cell, cytoplasm expands, but unable to burst because of pressure from cell wall (turgor).

Active Transport

Moves ions or molecules against a concentration gradient using energy (ATP).

Examples of Active Transport

• Plants move minerals (inorganic ions) into their roots.

• The gills of marine fish can remove salt from the body by pumping it into the salt water.

Bulk Transport

Endocytosis and Exocytosis are used for materials that are too big to pass through the plasma membrane (eg. proteins).  Transport occurs through the formation of vesicles.

Endocytosis

 Cell engulfs material to bring it into the cell.

• Endocytosis of fluids is PINOCYTOSIS.

• Endocytosis of solid material PHAGOCYTOSIS.

Exocytosis

• Moves material to the outside of the cell.

• Vesicle fuses with the plasma membrane and discharges contents to the outside.

• Fusion of vesicles to the plasma membrane adds membrane to the cell surface.

Light Microscopes

Magnification: 300x or 2000x

Whole parts, can be living

Outer details, some structures inside

Electron Microscopes

Magnification: 2 million x

Must be dead

Detailed structures

Cell Theory

1. All living things are made of cells.

2. Cells are the smallest basic units of life.

3. All cells come from pre-existing cells.

Domains and Kingdoms of Life

3 Domains: Bacteria, Archaea, Eukarya.

Bacteria and Archaea are all prokaryotes, and Eukarya is eukaryotic and divided into distinct Kingdoms.

MRSGREEN Criteria for Organism Consideration

• Movement

• Respiration

• Sensitivity to stimuli

• Growth

• Reproduction

• Equilibrium (Homeostasis)

• Excretion

• Nutrition

Multicellular Organism Order

Cell: Basic unit of life.

Tissue: Group of cells with similar structure and function. Eg. Smooth muscle cells= Smooth muscle tissues.

Organ: Grouping of tissues into distinct structures to perform a specialised job. 

System: Group of organs work together to perform a particular task. Eg. reproductive system.

Binary Fission

1. The one circular chromosome replicates and the copies attach to the cell membrane. Plasmids will also replicate

2. The cell begins to grow.

3. The cell continues to grow, elongating further.

4. The cell membrane (and cell wall) pinches inwards to divide the cell into two. (Cytokinesis)

5. Two daughter cells are produced, each genetically identical to each other and the original cell.

Cytokinesis

Division of the cytoplasm and formation of two daughter cells.

Septum

A dividing wall formed during binary fission.

How is cytokinesis different in plant and animal cells?

Animal cells form a cleavage furrow, then pinch apart.

Plant cells form a cell plate in the middle from vesicles accumulating, and new cell walls are formed.

DNA

• Deoxyribonucleic acid

• A molecule that is the blueprint of all living things. 

• Contains the instructions needed for an organism to develop, survive and reproduce.

DNA Structure

• Two strands or "backbones"made of phosphate bonded together and twist around each other: A double helix.

• Backbones are bonded together by hydrogen bonds.

• Each "rung" of the ladder is made up of two smaller molecules, known as bases: Adenine (A), thymine (T), guanine (G) and cytosine (C).

• Base pairs are complementary.

• Adenine (A) and Thymine (T) join together: A–T

• Guanine (G) and Cytosine (C) join together: G–C

DNA Molecule

The DNA molecule is made up of small parts (monomers) called nucleotides. A DNA nucleotide itself has 3 parts:

• A phosphate group

• A deoxyribose sugar

• A nitrogenous base (one of A, T, C or G) 

DNA Replication

• DNA replication needs to occur so that there is enough DNA for cell division (mitosis or meiosis). It ensures that each new cell made by cell division gets a copy of the genome.

• DNA replication is semi-conservative, meaning that each strand in the DNA double helix molecule acts as a template for the synthesis of a new, complementary strand.

• The hydrogen bonds of  the DNA double helix unwind, and the helix opens. Each strand of DNA acts as a template for synthesis of a new complementary strand. Complementary pairs are added to each strand, and replication produces 2 identical DNA double helices, with one new and one old strand.

Chromosomes

Made of chromatin, a single long strand of DNA coiled around proteins called histones.