Cell Structures and Functions

• Eukaryotic cells have a nucleus and membrane-bound organelles.
• Prokaryotic cells lack a nucleus and have simpler structures.

Cell Organelles and Functions

• Nucleus: Contains genetic material and controls cell activities.
• Mitochondria: Powerhouse of the cell.
• Ribosomes: Site of protein synthesis.
• Endoplasmic Reticulum: Transports materials.
• Golgi Apparatus: Modifies and packages proteins.
• Lysosomes: Break down waste and worn-out cell parts.
• Chloroplasts (plants only): Conduct photosynthesis.
• Cell Wall (plants only): Provides structure and support.
• Cell Membrane: Controls movement of substances in and out of the cell.

Plant vs Animal Cells

• Both plant and animal cells have a nucleus, mitochondria, ribosomes, and cytoplasm.
• Plant cells have a cell wall, chloroplasts, and a large central vacuole.
• Animal cells do not have a cell wall, chloroplasts, or a large central vacuole.

Specialized Cells

• Specialized cells have unique structures adapted for specific functions.
• Examples of specialized cells include nerve cells for transmitting signals and red blood cells for carrying oxygen.
• Specialized cells allow organisms to have complex functions by performing specific tasks efficiently.
• Muscle cells contracting for movement and root hair cells absorbing water in plants are specific tasks performed by specialized cells.

DNA Structure and Function

• DNA is a double helix made of nucleotides, each containing a sugar, phosphate, and nitrogen base (A, T, C, G).
• Adenine (A) pairs with Thymine (T) and Cytosine (C) pairs with Guanine (G).
• DNA stands for Deoxyribonucleic Acid.
• It carries genetic instructions for the growth, development, and reproduction of living organisms.

Genes, Alleles, and Inheritance

• Genes are segments of DNA that determine traits.
• Alleles are different versions of a gene.
• Characteristics are passed down through inheritance.
• Children receive one allele from each parent.

Mutations

• Mutations can lead to genetic variation, some beneficial (evolution), and some harmful (diseases).

Genes and Variation

• Different combinations of genes and alleles create diversity in traits.
• Genes regulate processes like cell division and DNA repair, which affect aging.
• Mutations or damage over time can lead to aging-related changes.

Mitosis and the Cell Cycle

• Mitosis is a type of cell division that results in two identical daughter cells, important for growth and repair.
• The stages of the cell cycle are: Interphase, Mitosis, and Cytokinesis.

Phases of Mitosis

• Interphase: DNA in the cell is copied in the nucleus.
• Prophase: Chromosomes condense, the nuclear membrane breaks down, and chromosomes pair up.
• Metaphase: Chromosomes align in the center and spindle fibers appear.
• Anaphase: Sister chromatids are pulled apart.
• Telophase: Two new nuclei begin to form as the cell pinches in the middle.
• Cytokinesis: Two identical daughter cells are created.

Cell Dysfunction and Natural Selection

• If cells do not function correctly, it can lead to diseases like cancer, where cells divide uncontrollably.
• Natural selection is the process where individuals with advantageous traits survive and reproduce.
• Organisms best adapted to their environment are more likely to pass on their traits.
• Natural selection favors traits that improve survival, exemplified by white rabbits in a snowy environment.

Extinction and Microscopes

• Extinction occurs when a species dies out, but conservation efforts like habitat protection and breeding programs help preserve species.
• Using a microscope involves preparing slides, adjusting focus, and using different magnifications to observe structures.

Stomata and Their Purpose

• Stomata are small pores on the surface of leaves that regulate gas exchange and water loss.
• They allow carbon dioxide in for photosynthesis and release oxygen and water vapor.
• Plants in humid environments tend to have more stomata to maximize gas exchange.
• Plants in dry environments have fewer stomata to reduce water loss.

Bacterial Cells and Classification

• Bacterial cells contain organelles such as plasmids, nucleoid, flagella, and pili.
• Eukaryotes include animals, plants, fungi, and protists.
• Prokaryotes include bacteria.

Viruses

• A virus is a tiny infectious agent that can only reproduce inside a host cell.
• It is made of genetic material enclosed in a protein coat.
• Viruses include COVID-19 (SARS-CoV-2), which is a coronavirus that infects human respiratory cells, causing symptoms like fever, cough, and difficulty breathing.

Microscope and Cells

• The field of view is the visible area seen through the microscope lens, and it decreases as magnification increases.
• Magnification calculation: If the eyepiece is 10x and the objective lens is 40x, then multiply to get a total magnification of 400x.
• Chromosomes are structures made of DNA and proteins that carry genetic information.
• Humans have 46 chromosomes (23 pairs), with one set inherited from each parent.

Specialized Cells and Stem Cells

• Nerve cells transmit electrical signals throughout the body.
• Muscle cells contract to enable movement.
• Red blood cells carry oxygen using hemoglobin.
• Palisade cells found in leaves contain chloroplasts for photosynthesis.
• Xylem cell transports water and minerals from roots to leaves in plants.
• Phloem cells transport sugars and nutrients throughout the plant.
• Stem cells are undifferentiated cells that can change into various types of cells, regenerate damaged tissues, but their use raises ethical concerns about sourcing and consent.