Science 10 Unit C Biology Review

Cell Theory

• All living things are made of cells, which are the basic structural and functional units of life.

• All life functions occur in cells, highlighting the cell as the fundamental unit of physiological activity.

• All cells come from pre-existing cells through cell division, emphasizing that cells do not spontaneously generate (law of biogenesis).

Details on Cell Theory

1. Cell as the Basic Unit of Life:

   • Cells are the smallest entities capable of performing life functions.

   • They contain all the hereditary material (DNA) necessary for directing cellular activities and transmitting information to the next generation.

2. Life Functions in Cells:

   • Cells conduct various processes, including metabolism, growth, response to stimuli, and reproduction.

   • Organelles within the cell perform specific functions necessary for the cell’s survival.

3. Origin of Cells:

   • This principle opposes the idea of spontaneous generation.

   • Cell division involves processes like mitosis and meiosis, ensuring genetic continuity.

Plant vs. Animal Cells

• Animal cells have centrioles, which are involved in cell division; plant cells do not possess centrioles, relying on other mechanisms for cell division.

• Plant cells have cell walls, providing structural support and protection, along with chloroplasts for photosynthesis; animal cells lack both.

• Animal cells have smaller vacuoles and vesicles used for storage and transport; plant cells usually have one large central vacuole to maintain cell turgor and store nutrients and waste.

Detailed Differences

1. Centrioles:

   • Animal cells use centrioles to organize microtubules during cell division.

   • Plant cells utilize other structures like the phragmoplast for cell plate formation during cytokinesis.

2. Cell Walls and Chloroplasts:

   • Plant cell walls are primarily made of cellulose, offering rigidity.

   • Chloroplasts conduct photosynthesis, converting light energy into chemical energy in the form of glucose.

3. Vacuoles and Storage:

   • Plant cells' large central vacuole helps maintain turgor pressure, essential for plant rigidity.

   • Animal cells have numerous smaller vacuoles and vesicles for diverse functions like storage and transport.

Microscope Parts

• Ocular Lens: Focuses the image into the eye, typically providing a magnification of 10x.

• Revolving Nose Piece: Selects the objective lens with varying magnifications.

• Objective Lenses (Low, Medium, High Power): Provide different levels of magnification (e.g., 4x, 10x, 40x, 100x).

• Stage Clip: Holds the slide securely in place on the stage.

• Diaphragm: Adjusts the amount of light passing through the specimen, enhancing contrast.

• Light Source: Provides illumination to view the specimen.

• Stage: Platform that supports the slide.

• Arm: Connects the objective lenses and stage to the microscope's base, used for carrying the microscope.

• Course/Fine Adjustment: Knobs used to bring the specimen into focus, with the coarse adjustment used for initial focusing and the fine adjustment for detailed clarity.

• Base: Supports the microscope, providing stability.

Functionality Details

1. Magnification System:

   • Objective lenses range from low (4x) to high power (100x), influencing the total magnification.

   • Total magnification is the product of objective lens magnification and ocular lens magnification (Total = Ocular \; Lens \; Magnification \times Objective \; Lens \; Magnification).

2. Illumination and Contrast:

   • The diaphragm controls the amount of light, affecting image contrast and clarity.

   • Proper illumination is crucial for clear observation of the specimen's details.

3. Focusing Mechanisms:

   • Coarse adjustment knob allows large changes in focus, useful for initial adjustments.

   • Fine adjustment knob provides precise focusing for detailed observation.

Conversions

• 1 \; mm = 1000 \; \mu m (Micrometers)

Additional Conversions

• 1 \; cm = 10 \; mm

• 1 \; m = 1000 \; mm

• 1 \; \mu m = 1000 \; nm (Nanometers)

Total Magnification

• Total \; Magnification = Ocular \; Lens \; Magnification \times Objective \; Lens \; Magnification

Example Calculation

• If the ocular lens is 10x and the objective lens is 40x, then:
  Total \; Magnification = 10 \times 40 = 400x

Field of View (FOV) Calculation

• FOV{low} \times Magnification{low} = FOV{high} \times Magnification{high}

Usage

1. Purpose:

   • To determine the field of view at a higher magnification when the field of view at a lower magnification is known.

2. Example:

   • If FOV{low} = 2 \; mm, Magnification{low} = 40x, and Magnification{high} = 100x, then: 2 \; mm \times 40 = FOV{high} \times 100
     FOV_{high} = \frac{2 \; mm \times 40}{100} = 0.8 \; mm

Cell Structures and Functions

• Mitochondria: Produces ATP through cellular respiration.

• Ribosomes: Produce proteins by translating mRNA.

• Vacuoles: Store food, water, or wastes; in plant cells, they maintain turgor pressure.

• Nucleus: Contains DNA, which controls cell activities.

• Chloroplast: Converts solar energy to chemical energy via photosynthesis (in plant cells).

• Lysosome: Digests cellular materials, breaking down waste and debris within the cell.

• Cell Wall: Protects the cell membrane, providing structural support and shape (in plant cells, made of cellulose; in bacteria, made of peptidoglycan).

• Golgi Apparatus: Packages and modifies proteins and lipids for secretion or internal use.

• Endoplasmic Reticulum (ER): Intracellular transport network; rough ER has ribosomes for protein synthesis, while smooth ER synthesizes lipids and steroids.

• Cell Membrane: Acts as the "gatekeeper" of the cell, regulating the movement of substances in and out.

Elaborations

1. Energy Production & Synthesis:

   • Mitochondria use oxygen to produce ATP, the energy currency of the cell.

   • Ribosomes are found freely in the cytoplasm or attached to the rough ER.

2. Storage & Genetic Control:

   • Vacuoles store water, ions, and macromolecules.

   • The nucleus houses chromatin, which condenses into chromosomes during cell division.

3. Specialized Organelles:

   • Chloroplasts contain chlorophyll, which captures light energy.

   • Lysosomes contain enzymes to break down complex molecules.

4. Transport & Protection:

   • The Golgi apparatus modifies and sorts proteins, directing them to specific locations.

   • The ER facilitates protein folding and lipid synthesis.

5. Membrane Functions:

   • The cell membrane is composed of a phospholipid bilayer with embedded proteins.

   • It controls the passage of ions, nutrients, and waste.

Term Definitions

• Isotonic: Solution with the same solute concentration as the cell, resulting in no net movement of water.

• Hypertonic: Solution with a higher solute concentration than the cell, causing the cell to lose water and shrink (plasmolysis).

• Hypotonic: Solution with a lower solute concentration than the cell, causing the cell to absorb water and swell (cytolysis).

• Osmosis: Diffusion of water across a selectively permeable membrane from an area of high water concentration to an area of low water concentration.

• Diffusion: Movement of particles from an area of high concentration to an area of low concentration until equilibrium is reached.

• Semi-permeable: Membrane that allows only certain particles through while restricting others based on size, charge, or chemical properties.

• Concentration Gradient: The difference in solute concentration between two areas; particles move down the gradient from high to low concentration.

• Equilibrium: State of balance between opposing actions, where the net change is zero.

Explanations

1. Tonicity:

   • Isotonic solutions maintain cell volume and function.

   • Hypertonic solutions can lead to cell dehydration.

   • Hypotonic solutions may cause cells to burst.

2. Membrane Transport:

   • Osmosis is crucial for maintaining cell turgor and hydration.

   • Diffusion is vital for nutrient uptake and waste removal.

3. Selective Permeability:

   • Semi-permeable membranes ensure cells maintain specific internal environments.

   • They regulate the passage of essential molecules.

4. Concentration Dynamics:

   • The concentration gradient drives passive transport processes.

   • Equilibrium ensures stability in cellular environments.

Balanced Chemical Equations

• Photosynthesis: 6CO2(g) + 6H2O(l) \rightarrow C6H{12}O6(aq) + 6O2(g)

  • Carbon dioxide + Water yields Glucose + Oxygen

• Cellular Respiration: C6H{12}O6(aq) + 6O2(g) \rightarrow 6H2O(l) + 6CO2(g)

  • Glucose + Oxygen yields Water + Carbon dioxide

Details about Equations

1. Photosynthesis:

   • This process occurs in chloroplasts.

   • Light energy is converted into chemical energy.

2. Cellular Respiration:

   • This process occurs in mitochondria.

   • Glucose is broken down to produce ATP, water, and carbon dioxide.

Plant Hormones

• Auxins: Promote cell elongation; responsible for phototropism (growth towards light).

Auxin Functions

1. Phototropism:

   • Auxins accumulate on the shaded side of the plant, promoting cell elongation on that side.

   • This uneven growth causes the plant to bend towards the light.

2. Other Effects:

   • Involved in apical dominance, where the central stem is dominant over lateral buds.

   • Promotes root development and fruit growth.

Plant Transport

• Xylem: Transports water and minerals from roots to leaves (dead cells).

• Phloem: Transports food (sugars) from leaves to roots (alive cells).

• Cohesion: Water molecules stick to each other due to hydrogen bonds.

• Adhesion: Water molecules stick to other surfaces (like the walls of xylem).

Transport Mechanisms

1. Xylem Transport:

   • Relies on transpiration pull, cohesion, and adhesion.

   • Water moves up the plant through dead xylem cells.

2. Phloem Transport:

   • Uses active transport to load sugars into phloem.

   • Water follows by osmosis, creating pressure that pushes sugars to other parts of the plant.

Processes for Moving Water & Nutrients

• Osmosis/Diffusion, Adhesion/Cohesion, Transpiration.

Process Details

1. Osmosis/Diffusion:

   • Water moves into root cells via osmosis.

   • Nutrients move into root cells via diffusion.

2. Adhesion/Cohesion:

   • Water molecules stick together and to the walls of the xylem, aiding upward movement.

3. Transpiration:

   • Evaporation of water from leaves creates a pulling force that draws water up the xylem; regulates plant temperature, facilitates nutrient transport.

Plant Responses

• Tropisms: Plant responses to stimuli, which can be positive (growth towards the stimulus) or negative (growth away from the stimulus).

Types of Tropisms

1. Phototropism:

   • Response to light.

   • Stems exhibit positive phototropism, while roots might show negative phototropism.

2. Gravitropism:

   • Response to gravity.

   • Roots exhibit positive gravitropism, while stems exhibit negative gravitropism.

3. Thigmotropism:

   • Response to touch.

   • Seen in climbing plants like vines that wrap around structures for support.