Revision Notes

VCE Unit 1 Biology

This unit of study has explored the following ideas:

cell structure cell functioning composition of cells internal and external

environments of cells cell replication common requirements of living

things reproduction

Key Knowledge

The Cell Theory states that: All organisms are made up of cells and/or

the products of cells All cells are derived from pre-existing cells The cell is the smallest organisational unit

of a living thing

Prokaryotic cells are relatively small and primitive. They lack membrane bound organelles. The DNA is free floating in the cytoplasm. Bacteria and cyanobacteria are prokaryotic.

Eukaryotic cells are relatively larger and more complex, containing membrane bound organelles including a nucleus. Protists, Fungi, Plants and Animals are all eukaryotic.

Cell Structure

Cell Organelles Nucleus – Controls cell activities Mitochondrion – site of aerobic stages of

cellular respiration Ribosomes – site of protein synthesis Endoplasmic reticulum – protein synthesis

and transport within the cell Golgi Body – packaging of substances in

preparation for secretion from cell Chloroplast – site of photosynthesis Lysosomes – produce digestive enzymes

within cells Vacuoles – storage sacs for dissolved

substances Cell Wall – contributes to structural

support of the plant Plasma Membrane – partially permeable,

flexible barrier controlling what comes in and goes out of the cell

Cell Functioning

Photosynthesis This process occurs in the chloroplasts of

plant cells as they contain the pigment chlorophyll

Converts inorganic substances and light energy into the organic energy store – glucose.

This is an endergonic process requiring a net input of energy (Anabolic)

6CO2 + 12H2O C6H12O6 + 6O2 + 6H20 Cellular Respiration

This process occurs in the cytosol and mitochondria of all living things

Glycolysis – occurs anaerobically in the cytosol releasing 2 ATP

Krebs Cycle – occurs within the mitochondria releasing 2 ATP

Electron Transfer – occurs within the mitochondria releasing 32 – 34 ATP

This is an exergonic process requiring a net output of energy (Catabolic)

C6H12O6 + 6O2 6CO2 + 6H20 + 36 – 38 units of ATP

Cell Functioning

Enzymes Proteins made by the cell to act as

biological catalysts Enzymes are specific binding with the

active sites of specific substrates Enzyme activity is affected by temperature

– at low temperature the enzyme is slow or dormant and at high temperature the active site changes shape and is said to be denatured.

Enzyme activity is also affected by pH. Each enzyme has a particular range of pH in which it works, above or below that the enzyme becomes denatured.

Cell Functioning

Chemical Components Carbohydrates – organic compounds

made up of C, H, O, N providing an energy source for cells.

Proteins – organic compounds made up of C, H, O, N provide energy when consumed, structures

Lipids – organic compounds made up of C, H, O provide energy, used for energy storage, insulations, structure of membranes

Nucleic Acids – organic compounds made up of C, H, O, N, P contains the genetic code and involved in protein synthesis

Water – inorganic, all chemical reactions in organisms take place in solution

Minerals – inorganic – includes N, P, Fe, Mg – used in making organic compounds, components of haemoglobin and chlorophyll etc.

Vitamins – organic compounds, Vit C, Vit D for example operating as coenzymes

Composition of Cells

Plasma Membranes Diffusion

Diffusion is the movement of molecules of a substance from an area of high concentration of that substance to an area of low concentration

Osmosis Osmosis is the movement of water from an area

of low concentration of a dissolved substance to an area of high concentration of that dissolved substance.

Facilitated Diffusion. For non-lipid soluble chemicals, such as glucose,

diffusion occurs through the protein channel. Active Transport.

For chemicals that need to be moved against a concentration gradient it is required to use energy to move such chemicals through the protein channel.

Surface Area to Volume Ratio When substances enter or leave cells, the rate

at which they move is determined by a number of factors: concentration, temperature and the SA:V – the more SA for a particular V increases the speed of movement across the membrane,

Internal and External

Environments of Cells

Purposes of cell replication Maintenance – replace old or damaged cells Growth – parts of or whole organisms

Cell Cycle Interphase

G1 – pre DNA synthesis Synthesis – the chromosomes are copied G2 – post DNA synthesis

Mitosis Prophase – chromosomes uncoil becoming visible

and the nuclear membrane dissolves Metaphase – chromosomes line up along the equator

of the cell attaching to spindle fibres Anaphase – spindle fibres contract, causing

centromeres to split and the sister chromatids to move to the poles of the cell

Telophase – a new nuclear membrane forms and the chromosomes recoil and become indistinct.

Cytokinesis – the cell divides into two cells diving the cell contents reasonably equitably

Cell Replication

All living things are composed of cells and therefore need to: obtain nutrients and energy process nutrients distribute materials remove wastes exchange gases reproduce

Common Requirements of

Living Things

Autotrophs are capable of making their own organic compounds from inorganic substances.

Plants require carbon dioxide (gained via gas exchange), water, nitrogen, sulfur, magnesium, potassium, calcium and phosphorus for healthy growth (which are gained from the soil)

To gain energy plants create glucose in photosynthesis. This occurs in two stages: Light dependent – occurs in the grana, red

and blue light absorbed and energy is used to break water molecules

Light Independent – occurs in the stroma glucose is formed

Nutrition - Autotrophs

Heterotrophs also require energy and a range of macro and micro nutrients. However, heterotrophs are unable to create these for themselves and must consume other organisms.

This requires a digestive system: Mouth and teeth Oesophagus Stomach Small intestine Large intestine Rectum Anus Pancreas Liver and Bile Duct

Herbivores, Carnivores & Omnivores

Nutrition - Heterotrophs

In simple single celled organisms and small multicellular organisms distribution is achieved via diffusion.

In larger organisms systems are required to move materials around the organism.

Animals – blood, heart, arteries, arterioles, capillaries, veinules and veins.

Plants – phloem and xylem

Circulation

In animals, respiratory surfaces need to have: large surface area Thin, moist and easily penetrable surface Adequate ventilation Efficient transport of blood to the

respiratory surface Animals need to release carbon dioxide as

waste and take in oxygen. Plants also need to exchange

gases, but generally require carbon dioxide to enter and release water vapour and oxygen. Plants control gas exchange by the

opening and closing of stomata

Gas Exchange

In animals, the waste products of cellular respiration must be excreted.

Nitrogenous wastes take the form of ammonia, urea and uric acid

The organ responsible is the kidney.

In plants, there are no specialised organs as plants produce less waste and reuse some of the waste products

Waste Removal

Reproduction of organisms can occur via asexual or sexual means.

Asexual Occurs in single celled and simple

organisms and simple plants and animals All new individuals are identical to parents Does not require a mate Lack of genetic variety

Sexual Genetically unique individuals are formed Fusion of haploid gametes to produce

diploid zygote Requires a male and a female External fertilisation Internal fertilisation

Reproduction