Biology IGCSE part 1 Flashcards

(a) movement as an action by an organism or part of an organism causing a change of position or place

(b) respiration as the chemical reactions in cells that break down nutrient molecules and release energy for metabolism

(c) sensitivity as the ability to detect and respond to changes in the internal or external environment

(d) growth as a permanent increase in size and dry mass

(e) reproduction as the processes that make more of the same kind of organism

(f) excretion as the removal of the waste products of metabolism and substances in excess of requirements

(g) nutrition as the taking in of materials for energy, growth and development

A group of organisms that can reproduce to produce fertile offspring.

An internationally agreed system in which the scientific name of an organism is made up of two parts showing the genus and species.

• Genus: The first name, always capitalized, indicating the broader group to which the organism belongs.
• Species:The second name, always in lowercase, specifying the particular species within that genus.

Explain that classification systems aim to reflect evolutionary relationships.

Explain that the sequences of bases in DNA are used as a means of classification. Groups of organisms which share a more recent ancestor (are more closely related) have base sequences in DNA that are more similar than those that share only a distant ancestor.

Animals that have a vertebral column (spine).

Animals that don't have a vertebral column (spine).

Head, thorax and abdomen

Animal, plants, fungus, prokaryote, protoctist

Similarities:

• Cell Membrane:Both plant and animal cells have a cell membrane that encloses the cell and regulates the movement of substances in and out.
• Nucleus:Both cell types contain a nucleus, which houses the cell's DNA and controls its activities.
• Cytoplasm:The cytoplasm is the gel-like substance within the cell where organelles are located and many metabolic reactions occur in both plant and animal cells.
• Ribosomes:Ribosomes, the sites of protein synthesis, are present in both plant and animal cells.
• Mitochondria:Both cell types contain mitochondria, the powerhouses of the cell, responsible for energy production.

Differences:

• Cell Wall:Plant cells have a rigid cell wall made of cellulose located outside the cell membrane, providing structural support and protection. Animal cells lack a cell wall.
• Chloroplasts:Plant cells contain chloroplasts, organelles containing chlorophyll, which capture sunlight and convert it into chemical energy through photosynthesis. Animal cells do not have chloroplasts.
• Vacuoles:Plant cells often have a large central vacuole that stores water, nutrients, and waste products and helps maintain cell turgor. Animal cells may have smaller, numerous vacuoles.

• Cell Wall: provide structure and protection. In bacteria, the cell wall is made of a substance called peptidoglycan, which is different from the cellulose cell walls found in plants.
• Cell Membrane: A selectively permeable membrane that regulates the movement of substances in and out of the cell.
• Cytoplasm: The gel-like substance within the cell membrane that contains all the cell's internal structures and where many of the cell's chemical reactions take place.
• Ribosomes: Structures responsible for protein synthesis. Bacterial ribosomes have a different structure compared to those in eukaryotic cells.
• Circular DNA: Bacteria do not have a nucleus.The DNA of bacterial cells is found loose in the cytoplasm. It is called chromosomal DNA.
• Plasmids: Small, circular DNA molecules that carry genes separate from the main chromosome.They can replicate independently and may contain genes that provide bacteria with advantages like antibiotic resistance.

Plant

• Structural Support: Provides rigidity, maintaining the cell's shape.
• Water Regulation: Prevents the cell from absorbing too much water.
• Protection: Shields against mechanical stress and pathogenic invasion

Bacteria

• Shape Maintenance: Gives the cell its characteristic shape.
• Environmental Barrier: Protects against external threats and osmotic pressure.

• Selective Permeability: Regulates the entry and exit of substances.
• Signal Reception: Contains receptors for cellular communication.
• Interaction with Environment: Enables cell to respond to external changes.

• Genetic Storage: Houses chromosomes with genetic information.
• Regulation of Gene Expression: Controls cellular activities by regulating DNA transcription.
• Ribosome Production: The nucleolus within the nucleus produces ribosomes.

• • Metabolic Reactions: Hosts numerous biochemical processes.
  • Medium for Molecular Movement: Facilitates the transport of molecules within the cell.
  • Structural Support: Gives cells their shape and keeps organelles in place.

• Photosynthesis: Converts solar energy into glucose, a vital energy source.
• Starch Storage: Stores glucose in the form of starch.
• Oxygen Production: Releases oxygen as a byproduct of photosynthesis.

• Protein Synthesis: Translates mRNA into amino acid chains (proteins).
• Enzyme Production: Produces enzymes essential for various cellular processes.

Produce the energy-carrying molecule ATP (adenosine triphosphate). This process releases energy from glucose, fueling various cellular activities.

• Storage: Holds water, nutrients, and waste products.
• Turgor Pressure Maintenance: Contributes to cell rigidity.
• Regulates the cell’s internal pH and ion balance.

• Genetic Information: Carries genes essential for survival and reproduction.
• Adaptation and Survival: Plasmids often contain genes for antibiotic resistance.

New cells are produced by division of existing cells

(a) ciliated cells – movement of mucus in the

trachea and bronchi

(b) root hair cells – absorption

(c) palisade mesophyll cells – photosynthesis

(d) neurones – conduction of electrical impulses

(e) red blood cells – transport of oxygen

(f) sperm and egg cells (gametes) – reproduction

Basic building block of all living organisms.

A group of specialised cells working together to carry out a specific function.

A group of specialised tissues working together to carry out a specific function.

A group of specialised organs working together to carry out a specific function.

A living thing.

magnification = image size ÷ actual size

1 millimetre (mm) = 1,000 micrometres (μm)

The net movement of particles from a region of their higher concentration to a region of their lower concentration (i.e. down a concentration gradient), as a result of their random movement.

Happens due to kinetic energy of particles causing random movement.

Surface area: the larger the surface area, the more space there is for particles to diffuse across, increasing the rate of diffusion.

Temperature: higher temperatures give particles more energy, allowing them to move faster. This increases the rate of diffusion.

Concentration gradients: The steeper the concentration gradient, the greater the difference in concentrations. This means, more particles will move from their region of higher concentration to their region of lower concentration to achieve equilibrium, thereby increasing the rate of diffusion.

Diffusion distance: this is the distance that particles have to travel to achieve equilibrium. The smaller the diffusion distance, the less time it takes to achieve equilibrium, so higher the rate of diffusion.

Describe osmosis as the net movement of water molecules from a region of higher water potential (dilute solution) to a region of lower water potential (concentrated solution), through a partially permeable membrane.

• Dialysis tubing, simulating a cell membrane, allows selective passage of water and small solutes.
• Fill the tubing with a sugar or salt solution and submerge it in distilled water or another solution with varying solute concentration.

Change in volumes or mass shows what way osmosis went.

The pressure water applies in plants is turgor pressure and turgidity is the state of being ‘turgid'. Plants need turgid cells to help them maintain their shape and in turn, help the plant stay upright. Water is mainly stored in the vacuole in the cytoplasm, and it is mainly this vacuole that regulates the turgidity of a plant cell.

• When you immerse plant tissue in solutions of lower water potential (hypertonic solution) than the plant cells:

Water diffuses out of the cell by osmosis. This causes the cytoplasm to shrink, and thus the cell membrane gets ripped away from the cell wall. This process is called plasmolysis. Cells become weak and flaccid, as there isn’t enough cytoplasm to support the cell and help it maintain its shape.

• When you immerse plant tissue in a solution of equal water potential to their cell cytoplasm (isotonic solution).

Since the concentration of the solution is equal inside and outside of the plant cells, there is no net movement of water. This means the volume or shape of the plant cell is unlikely to change.

1. When you immerse plant tissue in solutions of higher water potential than their cell cytoplasm (hypotonic solution).

Water diffuses down its concentration gradient into the cell, by osmosis. This causes the amount of cell matter inside the cell to increase. As the cytoplasm enlarges, it pushes outwards on the cell surface membrane more and more. Normally, this would usually cause the cell surface membrane to eventually burst (once the turgor pressure grows too large). However, plant cells have very strong cell walls. This holds the plant cell intact, and as the cytoplasm pushes outside, the cell simply swells to its full size and becomes rigid. This cell is turgid.

The movement of particles through a cell membrane from a region of lower concentration to a region of higher concentration (i.e. against a concentration gradient), using energy from respiration.

protein carriers

• uptake of glucose by epithelial cells in the villi of the small intestine
• uptake of ions from soil water by root hair cells in plants

Carbon, Hydrogen and Oxygen.

Carbon, Hydrogen and Oxygen.

Carbon, Hydrogen and Oxygen, and Nitrogen. sometimes sulfur and phosphorus too

glucose

amino acids

fatty acids and glycerol

Add a few drops of iodine to the test solution/ test material. If it contains starch, the solution will turn blue-black, if not, it’ll remain an orangey/ brown colour (the colour of iodine).

To a known volume of test solution, add the equal volume of Benedict’s reagent/ solution. Give it a stir and look for any colour changes. (If none, try heating it in a warm water bath (about 80^oC), and look for any colour changes.)

If stays blue, there are no reducing sugars present .

If there are any sugars present, it’ll change from blue to green, to yellow, to orange, to red. Green means that there are very low reducing sugars and red the most.

Note: sucrose is not a reducing sugar.

Biuret reagent is a mix of two chemicals – copper sulfate (CuSO₄) mixed with either sodium hydroxide (NaOH) or potassium hydroxide (KOH).

To perform the test, simply add the biuret reagent to the test solution. (Note, if the test material is solid and not liquid, crush it and mix it with distilled water, to form a solution). 1:1 ratio of solution and reagent.

If peptide bonds are present, the blue reagent will turn mauve or purple.

Measure out a known volume of test solution into a test tube. About 1cm³ should be enough. Add the same volume of NaOH (or KOH) to the test tube and stir. Add a few drops of CuSO₄ solution, shaking after each drop. If buret reagent not already pre made

Add the test sample to a concentrated ethanol solution. You put the mixture into a test tube of distilled water, close it, and shake it around. If a cloudy emulsion forms, fats are present; if not, there are no fats.

1. Prepare the DCPIP solution: Dissolve DCPIP powder in distilled water to create a blue solution.

2. Prepare the sample:If the sample is a solid it needs to be ground or crushed and mixed with distilled water to form a solution.

3. Titration:Add the sample solution dropwise to a fixed volume of the blue DCPIP solution in a test tube.

4. Observe the color change: Swirl the test tube gently after each drop. The blue color of the DCPIP will fade and eventually disappear (become colorless) when enough vitamin C has been added to reduce all the DCPIP.

5. Determine the concentration: The lower the volume of sample needed, the higher the vitamin C concentration in that sample.

Litmus - Red in acid, blue in alkaline.

• Hydrogencarbonate Color changes:
  • Yellow: High carbon dioxide concentration (acidic pH).
  • Red: Normal carbon dioxide concentration (neutral pH).
  • Purple: Low carbon dioxide concentration (alkaline pH).

In IGCSE Biology, methylene blue dye is used as an indicator to measure the rate of aerobic respiration in living cells like yeast. As the yeast respire, they release hydrogen ions that reduce the dye, causing it to change from blue to colorless. The time it takes for this color change to occur is a measure of the respiration rate; a shorter time indicates a faster rate.