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August 2026 Ultimate Life Science: Biology Regents Review | EVERYTHING YOU NEED TO KNOW
Shsat review
Overview
This video provides a comprehensive review of key life science and biology topics relevant to the 2026 Regents exam. It covers fundamental concepts such as cell theory, biomolecules, cell types (prokaryotic vs. eukaryotic, plant vs. animal), homeostasis, body systems, energy flow (photosynthesis, respiration), ecological concepts (food webs, cycles), genetics (DNA, protein synthesis), and human impact on the environment. The review aims to condense a year's worth of learning into an accessible format, emphasizing understanding of core principles and their interconnections.
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Chapters
- Cell theory states that all living things are composed of cells, which are the basic units of life.
- Cells are fluid-filled compartments enclosed by a cell membrane, containing cytoplasm and various biomolecules.
- The four major classes of biomolecules are carbohydrates (energy), lipids (membranes, energy storage), proteins (structure, enzymes, signaling), and nucleic acids (DNA, RNA).
- Proteins' function is determined by their structure, and they are built from amino acids.
- Nucleic acids form the building blocks of DNA and RNA, which carry genetic information.
Understanding the fundamental structure and components of cells is crucial because cells are the basic units of all life, and their functions dictate the health and operation of all living organisms.
Glucose (C6H12O6) is a carbohydrate that provides a quick energy source for cells, being converted into ATP.
- Prokaryotic cells are simple, lacking a nucleus and membrane-bound organelles, with DNA freely floating in the cytoplasm.
- Eukaryotic cells are more complex, featuring a nucleus to house DNA and various membrane-bound organelles that compartmentalize functions.
- Key organelles include the nucleus (control center), mitochondria (energy production via cellular respiration), ER (protein synthesis, lipid metabolism), Golgi apparatus (packaging and transport), lysosomes (waste breakdown), and ribosomes (protein synthesis).
- Plant cells possess additional structures like a cell wall for rigidity and chloroplasts for photosynthesis, distinguishing them from animal cells.
Differentiating between cell types and understanding the roles of organelles helps explain the diverse functions within organisms, from energy production to genetic control and waste management.
Mitochondria are the 'powerhouses' of the cell, converting sugar into ATP, the energy currency for cellular activities.
- Homeostasis is the maintenance of a stable internal environment within an organism, achieved through the coordinated function of its parts.
- Organisms are organized hierarchically: cells form tissues, tissues form organs, organs form organ systems, and organ systems work together to maintain life.
- Major body systems include digestive, respiratory, circulatory, nervous, endocrine, immune, excretory, and musculoskeletal systems, each with specific functions.
- Feedback mechanisms, like the insulin-glucagon loop regulating blood sugar, are essential for maintaining homeostasis.
Understanding homeostasis and body systems explains how complex organisms maintain internal balance and coordinate functions to survive and respond to environmental changes.
During exercise, the musculoskeletal system's increased energy demand triggers faster breathing (respiratory system) and increased heart rate (circulatory system) to supply more oxygen and nutrients.
- Photosynthesis, occurring in chloroplasts, converts light energy, CO2, and water into glucose (sugar) and oxygen, primarily performed by producers (plants).
- Cellular respiration, occurring in mitochondria, breaks down glucose using oxygen to produce ATP (energy), carbon dioxide, and water, performed by both plants and animals.
- Energy flows through ecosystems via food chains and food webs, with producers at the base and energy decreasing at each successive trophic level (typically 10% transfer).
- Biomass, the total mass of organisms at a trophic level, also decreases as you move up the food chain.
- Biogeochemical cycles, such as the carbon, nitrogen, and water cycles, describe the movement of essential elements through Earth's spheres (atmosphere, hydrosphere, biosphere, geosphere).
Understanding energy flow and matter cycling is fundamental to comprehending how ecosystems function, how energy is captured and transferred, and how essential elements are continuously reused.
A food chain might show shrubs (producer) being eaten by a deer (primary consumer), which is then eaten by a wolf (secondary consumer), illustrating the linear transfer of energy.
- Ecosystems are influenced by biotic (living) and abiotic (non-living) factors, which act as limiting factors that determine carrying capacity.
- Symbiotic relationships include mutualism (both benefit), commensalism (one benefits, other unaffected), and parasitism (one benefits, other harmed).
- Biodiversity, the variety of native species, contributes to ecosystem stability; invasive species disrupt this balance.
- Human activities like habitat destruction, pollution (greenhouse gases causing climate change), and resource depletion negatively impact ecosystems.
- Conservation efforts, resource management (renewable energy, recycling), and protecting natural habitats are crucial for environmental health.
This section highlights the interconnectedness of living organisms and their environment, emphasizing the importance of biodiversity and the significant consequences of human actions on ecological balance.
Invasive species like lanternflies lack natural predators, allowing their populations to explode, harming native plants and reducing biodiversity.
- DNA, a double helix structure made of nucleotides (A, T, C, G), carries the genetic code.
- Genes are segments of DNA that code for specific traits or proteins.
- Protein synthesis involves transcription (DNA to mRNA) and translation (mRNA to amino acid sequence at the ribosome).
- Mutations are random changes in DNA sequence that can alter protein function.
- Cell division (mitosis and meiosis) and reproduction are essential for growth, repair, and passing genetic information to offspring, leading to variation.
Understanding DNA, protein synthesis, and genetics explains how genetic information is stored, expressed, and passed down, forming the basis of inheritance and biological variation.
The DNA sequence 'ATCG' on one strand will have a complementary sequence 'TAGC' on the other strand due to base pairing rules (A with T, C with G).
Key takeaways
- Cells are the fundamental building blocks of all life, with specialized organelles performing specific functions.
- Homeostasis is the critical process by which organisms maintain a stable internal environment through coordinated system functions.
- Energy flows through ecosystems from producers to consumers, with significant energy loss at each trophic level.
- Biogeochemical cycles ensure the continuous recycling of essential elements necessary for life.
- Biodiversity enhances ecosystem stability, while human activities pose significant threats to environmental health.
- The genetic code stored in DNA dictates the synthesis of proteins, which in turn determine an organism's traits.
- Understanding the relationship between structure and function is key across all biological levels, from molecules to ecosystems.
Key terms
Cell TheoryBiomoleculesOrganellesProkaryotic CellEukaryotic CellHomeostasisPhotosynthesisCellular RespirationATPFood WebTrophic LevelCarrying CapacityBiodiversityInvasive SpeciesDNAGeneTranscriptionTranslationMutationFeedback Mechanism
Test your understanding
- How does the structure of a protein relate to its function, and what happens if this structure is altered?
- Explain the difference between prokaryotic and eukaryotic cells, focusing on the presence or absence of a nucleus and membrane-bound organelles.
- Describe the process of homeostasis and provide an example of how different body systems work together to maintain it.
- What is the role of producers in an ecosystem, and how does energy flow through different trophic levels?
- How does DNA store genetic information, and what are the key steps involved in synthesizing proteins from this information?
- What are the potential consequences of human activities like pollution and habitat destruction on ecosystem stability and biodiversity?