Cellular Processes and Division

This section delves into crucial cellular processes, including diffusion, osmosis, active transport, and cell division.

The guide explains diffusion as the random motion of particles from areas of high to low concentration. Osmosis is described as the movement of water molecules across a semi-permeable membrane from an area of low solute concentration to high solute concentration. Active transport is defined as the energy-requiring process of moving particles against a concentration gradient using transporter proteins.

Definition: Mitosis is a type of cell division used for growth and repair, producing two genetically identical daughter cells.

The text outlines the stages of mitosis, which include interphase, prophase, metaphase, anaphase, telophase, and cytokinesis. This process is crucial in answering the question, "What type of cell division results in growth?"

Highlight: The cell cycle phases in order are G1, S, G2 (collectively known as interphase), and M (mitosis).

The guide also touches on asexual reproduction, which produces genetically identical offspring, and the uncontrolled division of cancer cells leading to tumor formation.

Growth is defined as an increase in mass or length, and the text explains how percentage growth can be calculated and plotted on growth charts.

Vocabulary: Cell differentiation is the process by which cells become specialized for particular functions, often changing their shape or developing specific structures.

The section discusses stem cells, including adult and embryonic stem cells, and their potential use in treating injuries by replacing damaged cells. It also mentions the risk of cancer due to uncontrolled growth of stem cells.

Plant growth is explained, focusing on the zones of cell division (meristem), elongation, and specialization in roots and shoots. The text describes the formation of xylem vessels for water transport and the structure of root hair cells for efficient water absorption.

Nervous System and Genetics

This section covers the basics of the nervous system and introduces fundamental concepts in genetics.

The nervous system is described as comprising the central nervous system (brain and spinal cord) and peripheral nerves. The text explains how stimuli are detected by receptor cells and how impulses are transmitted through neurons to the brain or spinal cord.

Example: The reflex arc is described as: stimulus → receptor cell → sensory neuron → relay neuron in spine → motor neuron → effector (muscle) or brain.

The structure of neurons is detailed, including dendrites, dendrons, axons, and axon terminals. The myelin sheath, a fatty layer around neurons that speeds up neurotransmission, is also mentioned.

Vocabulary: A synapse is the gap between neurons or between a neuron and an effector (muscle or gland).

The section then transitions to genetics, starting with the formation of a zygote from gametes during fertilization. Meiosis, the process that produces gametes, is explained as a type of cell division that results in four genetically unique, haploid daughter cells.

Definition: DNA (Deoxyribonucleic Acid) is a polymer made of bases (A, T, G, and C) with a sugar-phosphate backbone. Base pairs are formed between A-T and G-C.

The text describes genes as sections of DNA that code for proteins and explains how different versions of genes (alleles) can result in variations of characteristics like eye color.

Highlight: Humans have 23 pairs of chromosomes, totaling 46 chromosomes.

The guide introduces the concepts of homozygous (same alleles) and heterozygous (different alleles) genotypes, as well as dominant and recessive alleles. It explains how these genetic factors influence the expression of traits in an organism's phenotype.

The section concludes by mentioning tools used in genetic analysis and prediction, such as Punnett squares and pedigree charts, which help visualize and calculate the probability of specific genetic outcomes in offspring.

Cell Structure and Function

This section provides a comprehensive overview of cell biology, focusing on the structure and function of different cell types.

Definition: Magnification is the product of objective and eyepiece magnification, while resolution is the smallest separation between points that can be measured.

The guide details the components of animal cell diagrams, including the nucleus, cytoplasm, membrane, ribosomes, and mitochondria. For plant cell diagrams, it adds chloroplasts, vacuoles, and cell walls to the list of organelles.

Highlight: The 10 differences between plant and animal cells primarily involve the presence of chloroplasts, large vacuoles, and cell walls in plant cells.

Specialized cells are discussed, such as:

• Sperm cells with tails, mitochondria, and enzyme-containing acrosomes
• Egg cells with abundant cytoplasm and a jelly coat
• Intestinal cells with microvilli
• Ciliated epithelial cells with hair-like structures for moving substances

The structure of bacterial cells is also explained, noting their prokaryotic nature and unique features like flagella, DNA loops, and plasmids.

Vocabulary: Prokaryotic cells lack a membrane-bound nucleus and other organelles found in eukaryotic cells.

The section concludes with an introduction to enzymes, defining them as biological catalysts that facilitate both breakdown (digestion) and synthesis reactions.

Example: Types of enzymes and their functions include:

• Protease: Breaks down proteins into amino acids
• Carbohydrase: Converts carbohydrates to glucose
• Lipase: Breaks down lipids into fatty acids and glycerol

The text explains the lock-and-key model of enzyme function and factors affecting enzyme activity, such as temperature and pH.