UPCAT Biology — Basic Life Functions & The CellRevision Notes
Revision notes for UPCAT Biology — Basic Life Functions & The Cell. Short, focused, and designed for the week before exam day. Use these when you are already familiar with the chapter and need a quick refresh on the high-yield items University of the Philippines tests.
Exam context
The University of the Philippines College Admission Test is conducted by University of the Philippines and is scheduled for Mid-2026 (announced by UP Admissions). The Biology subtest is marked as "Core" in the official pattern, and Basic Life Functions & The Cell appears in position 1st of 7 in the UPCAT Biology review rotation. Passing mark: UPG ≤ 2.2 typical. Recent UPCAT 2026 papers have drawn roughly 20 questions from this subject.
Basic Life Functions & The Cell - Revision notes
These revision notes cover the fundamental concepts of life processes and cellular biology essential for UPCAT and other Philippine college entrance tests. Understanding these topics is crucial as they form the foundation for all biological sciences and frequently appear in exam questions.
Sections
Exam Tips
- Remember MRS GREN acronym for quick recall in multiple choice questions
- Practice identifying life functions in different organisms (bacteria, plants, animals)
- Know specific examples for each function - examiners often ask for concrete examples
Key Points
- All living organisms exhibit seven basic life functions summarized by the acronym MRS GREN
- Movement: All organisms show movement at cellular or organism level (blood flow, muscle contraction, transport in plants)
- Respiration: Breakdown of nutrients to release energy through cellular respiration
- Sensitivity: Response to stimuli from internal and external environment
- Growth: Anabolic reactions occur faster than catabolic reactions, leading to increase in size or cell number
- Reproduction: Sexual or asexual reproduction ensures species survival
- Excretion: Removal of toxic wastes and excess substances (different from egestion)
- Nutrition: Obtaining and processing food for energy (autotrophs vs heterotrophs)
Definitions
Term
Anabolic Reactions
Definition
Chemical reactions that build complex molecules from simple substances, requiring energy input
Importance
Essential for growth and repair processes in living organisms
Term
Catabolic Reactions
Definition
Chemical reactions that break down complex substances to release energy
Importance
Provides energy for cellular activities and life processes
Term
Excretion vs Egestion
Definition
Excretion removes metabolic wastes; Egestion removes undigested food
Importance
Common exam distinction - excretion involves skin, kidneys, lungs
Section Title
Basic Life Functions (MRS GREN)
Common Mistakes
- Confusing excretion with egestion - excretion removes metabolic wastes, egestion removes undigested food
- Thinking plants don't show movement - they do at cellular level and in transport systems
- Forgetting that all seven functions must be present for something to be considered living
Exam Tips
- Memorize the 6 principles of cell theory - frequently tested
- Know the key differences table between prokaryotes and eukaryotes
- Remember historical contributors and their specific discoveries
Key Points
- Cell Theory: All living things are made of cells, cells are structural/functional units, cells arise from pre-existing cells
- Additional principles: cells contain hereditary information, same basic chemical composition, energy flow occurs within cells
- Prokaryotic cells: no membrane-bound nucleus, simple structure, found in bacteria and archaea
- Eukaryotic cells: membrane-bound nucleus and organelles, complex structure, found in plants, animals, fungi
- Key contributors: Robert Hooke (cork cells), Schwann (animal cells), Schleiden (plant cells), Virchow (cell division)
Definitions
Term
Prokaryotic Cell
Definition
Simple unicellular organism lacking nucleus and membrane-bound organelles
Importance
Represents earliest form of life, includes all bacteria and archaea
Term
Eukaryotic Cell
Definition
Complex cell with membrane-bound nucleus and specialized organelles
Importance
Found in all plants, animals, fungi, and protists - basis for multicellular life
Term
Peptidoglycan
Definition
Structural component of bacterial cell walls, absent in eukaryotes
Importance
Key distinguishing feature between prokaryotes and eukaryotes
Section Title
Cell Theory and Types
Common Mistakes
- Confusing prokaryote size with complexity - they can be large but are structurally simple
- Thinking all prokaryotes are harmful - many are beneficial or neutral
- Forgetting that prokaryotes have ribosomes (70S) while eukaryotes have 80S ribosomes
Exam Tips
- Use the comparison table between plant and animal cells for quick review
- Draw and label cell diagrams - visual memory helps in identification questions
- Know which organelles are found in both cell types vs unique to each type
Key Points
- Cell membrane controls substance movement in/out of cell
- Nucleus contains genetic material and controls cell activities
- Mitochondria generate ATP energy for cellular processes
- Chloroplasts (plants only) conduct photosynthesis using chlorophyll
- Endoplasmic reticulum: rough ER for protein synthesis, smooth ER for lipid synthesis
- Golgi apparatus modifies and packages proteins
- Ribosomes are sites of protein synthesis (70S in prokaryotes, 80S in eukaryotes)
- Lysosomes break down materials using digestive enzymes
- Vacuoles store materials (large in plants, small in animals)
Definitions
Term
Chloroplast
Definition
Organelle containing chlorophyll that conducts photosynthesis in plants
Importance
Converts light energy to chemical energy, produces oxygen as byproduct
Term
Mitochondria
Definition
Double-membraned organelle that produces ATP through cellular respiration
Importance
Called powerhouse of cell - essential for energy production in eukaryotes
Term
Ribosome
Definition
Small organelle composed of RNA and proteins where protein synthesis occurs
Importance
Present in all cells - essential for life as proteins control all cellular functions
Section Title
Cell Structure and Organelles
Common Mistakes
- Confusing organelle locations - chloroplasts only in plants, lysosomes mainly in animals
- Mixing up ER functions - rough ER has ribosomes for proteins, smooth ER for lipids
- Forgetting that plant cells have cell walls AND cell membranes
Formulas
Example
One glucose molecule requires 6 CO₂ molecules and 6 water molecules with light energy
Formula
6CO₂ + 6H₂O + light energy → C₆H₁₂O₆ + 6O₂
Variables
CO₂ = carbon dioxide, H₂O = water, C₆H₁₂O₆ = glucose, O₂ = oxygen
Application
Overall photosynthesis equation showing reactants and products
Exam Tips
- Memorize the overall photosynthesis equation - frequently appears in balanced equation questions
- Know the specific locations: light reactions in thylakoid, Calvin cycle in stroma
- Understand that 6 Calvin cycles needed to produce one glucose molecule
Key Points
- Overall equation: 6CO₂ + 6H₂O + light energy → C₆H₁₂O₆ + 6O₂
- Two stages: light-dependent reactions (thylakoid) and light-independent reactions (stroma)
- Light-dependent: uses photosystems I and II to produce ATP and NADPH
- Photosystem II (P680) splits water, releases O₂, pumps H⁺ ions
- Photosystem I (P700) reduces NADP⁺ to NADPH using electrons
- Chemiosmosis: H⁺ gradient drives ATP synthesis through ATP synthase
- Calvin Cycle: carbon fixation, G3P formation, RuBP regeneration
- RUBISCO enzyme fixes CO₂ to RuBP forming unstable 6C compound that splits into 3-PGA
Definitions
Term
Photosystem
Definition
Light-harvesting complex with proteins and pigments that capture light energy
Importance
Two photosystems work together to convert light energy to chemical energy
Term
Calvin Cycle
Definition
Light-independent reactions that fix CO₂ into organic molecules using ATP and NADPH
Importance
Produces G3P which is used to synthesize glucose and other organic compounds
Term
RUBISCO
Definition
Key enzyme that catalyzes carbon fixation by adding CO₂ to RuBP
Importance
Most abundant protein on Earth, essential for carbon fixation in photosynthesis
Section Title
Photosynthesis
Common Mistakes
- Confusing photosystem numbers with discovery order - PS II was discovered after PS I
- Thinking oxygen comes from CO₂ - it actually comes from water splitting
- Forgetting that Calvin cycle requires products from light reactions (ATP and NADPH)
Formulas
Example
One glucose molecule with six oxygen molecules produces six CO₂, six H₂O, and 32-38 ATP
Formula
C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + ATP
Variables
C₆H₁₂O₆ = glucose, O₂ = oxygen, CO₂ = carbon dioxide, H₂O = water, ATP = energy
Application
Overall cellular respiration equation opposite to photosynthesis
Exam Tips
- Know the ATP yield table by heart - commonly tested in calculation problems
- Understand the relationship between photosynthesis and cellular respiration equations
- Remember locations: glycolysis (cytoplasm), Krebs cycle (matrix), ETC (inner membrane)
Key Points
- Overall equation: C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + ATP
- Four stages: Glycolysis (cytoplasm), Pyruvate oxidation, Krebs cycle (mitochondrial matrix), Oxidative phosphorylation
- Glycolysis: glucose → 2 pyruvate, net gain 2 ATP and 2 NADH
- Pyruvate oxidation: pyruvate → acetyl CoA + CO₂ + NADH
- Krebs cycle: acetyl CoA enters 8-step cycle producing ATP, NADH, FADH₂, CO₂
- Electron transport chain: NADH and FADH₂ donate electrons, H⁺ pumped across membrane
- Chemiosmosis: H⁺ gradient drives ATP synthesis, oxygen serves as final electron acceptor
- Total yield: approximately 32-38 ATP per glucose molecule
Definitions
Term
Glycolysis
Definition
Anaerobic breakdown of glucose to pyruvate in cytoplasm yielding 2 ATP
Importance
First step of cellular respiration, occurs in all living cells
Term
Krebs Cycle
Definition
Series of 8 reactions in mitochondrial matrix that process acetyl CoA
Importance
Produces most NADH and FADH₂ for electron transport chain
Term
Electron Transport Chain
Definition
Series of protein complexes that transfer electrons and pump protons
Importance
Produces most ATP through chemiosmosis, requires oxygen
Section Title
Cellular Respiration
Common Mistakes
- Confusing ATP yields from different stages - glycolysis gives 2, not 4 net ATP
- Thinking all stages occur in mitochondria - glycolysis happens in cytoplasm
- Forgetting that fermentation is anaerobic respiration with different end products
Exam Tips
- Use PMAT acronym for mitosis stages
- Know the chromosome numbers: diploid (2n) vs haploid (n)
- Understand when crossing over occurs: prophase I of meiosis only
Key Points
- Cell cycle: Interphase (G0, G1, S, G2) and M phase (mitosis/meiosis + cytokinesis)
- Mitosis: produces 2 identical diploid cells for growth and repair
- Mitosis stages: Prophase, Metaphase, Anaphase, Telophase (PMAT)
- Meiosis: produces 4 genetically different haploid gametes
- Meiosis I: homologous chromosomes separate (reduction division)
- Meiosis II: sister chromatids separate (similar to mitosis)
- Sexual reproduction: involves gamete fusion, genetic diversity through crossing over
- Asexual reproduction: single parent, identical offspring, various methods
Definitions
Term
Mitosis
Definition
Cell division producing two identical diploid cells from one parent cell
Importance
Essential for growth, repair, and asexual reproduction in multicellular organisms
Term
Meiosis
Definition
Cell division producing four genetically different haploid gametes
Importance
Essential for sexual reproduction and genetic diversity
Term
Crossing Over
Definition
Exchange of genetic material between homologous chromosomes during meiosis I
Importance
Increases genetic diversity in offspring
Section Title
Cell Division and Reproduction
Common Mistakes
- Confusing mitosis and meiosis outcomes - mitosis gives 2 identical, meiosis gives 4 different
- Thinking crossing over happens in mitosis - it only occurs in meiosis I
- Forgetting that DNA replication happens before both mitosis and meiosis
Connections
- Photosynthesis and cellular respiration are complementary processes - products of one are reactants of the other
- Cell theory connects to all biology topics as cells are fundamental units of life
- ATP is the common energy currency linking photosynthesis, respiration, and all cellular processes
- Meiosis and genetic diversity connect to evolution and natural selection topics
- Cell structure relates to function - organelles have specific roles supporting life processes
- Both plant and animal cells follow same basic cell theory but have structural adaptations
Exam Strategy
Focus on memorizing key equations, organelle functions, and process locations. Practice drawing and labeling cell diagrams. Use acronyms like MRS GREN and PMAT for quick recall. Understand the relationships between processes rather than memorizing in isolation. Pay attention to numerical values (ATP yields, chromosome numbers) as these often appear in calculation problems.
Quick Review Questions
What are the seven basic life functions represented by MRS GREN?
This acronym helps remember all essential life processes that distinguish living from non-living things
What is the main difference between prokaryotic and eukaryotic cells?
This fundamental difference affects cell complexity and function
Write the balanced equation for photosynthesis.
This equation shows how plants convert CO₂ and water into glucose using light energy
Where do the light-dependent and light-independent reactions of photosynthesis occur?
Different locations allow for specialized functions within the chloroplast
What is the net ATP yield from glycolysis?
Glycolysis invests 2 ATP initially but produces 4 ATP, resulting in net gain of 2 ATP
How many cells are produced by mitosis vs meiosis?
Different purposes require different outcomes - growth/repair vs gamete formation
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