Unit 2 Cell Structure and Function
TERMINOLOGY
Cell: Smallest unit of life that can perform life functions.
Unicellular: Made of one cell; the cell performs all life functions.
Multicellular: Made of many cells with specialized functions.
Eukaryotic: Cell with a nucleus and membrane-bound organelles.
Prokaryotic: Cell without a nucleus or membrane-bound organelles.
Organelle: Specialized structure inside a cell with a specific function.
Tissue: Group of similar cells working together.
Organ: Group of tissues working together.
Organ system: Group of organs working together.
Cell membrane: Selectively permeable barrier surrounding the cell.
Lipid bilayer: Double layer of phospholipids forming the cell membrane.
Selectively permeable: Allows some substances through while blocking others.
Fluid mosaic model: Model describing the membrane as a flexible layer of lipids with proteins moving within it.
Peripheral membrane protein: Protein attached to the surface of the membrane.
Integral membrane protein: Protein embedded in or passing through the membrane.
Glycoprotein: Protein with a carbohydrate attached; helps with cell recognition and communication.
Hydrophilic: Attracted to water; “water-loving.”
Hydrophobic: Repelled by water; “water-fearing.”
Cytoplasm: Jelly-like material inside the cell where organelles are suspended.
Cytoplasmic streaming: Movement of cytoplasm that distributes materials throughout the cell.
Ribosome: Structure that makes proteins.
Protein synthesis: Process of making proteins using genetic instructions.
Endoplasmic reticulum (ER): Membrane system involved in making and transporting materials.
Rough ER: ER covered with ribosomes; makes and transports proteins.
Smooth ER: ER without ribosomes; makes lipids and helps detoxify substances.
Golgi apparatus: Modifies, sorts, and packages proteins and other materials.
Mitochondria: Produce ATP, the cell’s usable energy.
Enzymes: Proteins that speed up chemical reactions.
Cristae: Folds of the inner mitochondrial membrane that increase surface area for ATP production.
Lysosome: Breaks down waste, damaged organelles, and foreign materials.
Cytoskeleton: Network of proteins that gives the cell shape, support, and movement.
Microtubules: Cytoskeleton fibers involved in cell shape, movement, and chromosome movement.
Microfilaments: Thin cytoskeleton fibers involved in cell shape and movement.
Cilia: Short, numerous structures that move the cell or substances across its surface.
Flagella: Long structures that help a cell move.
Nucleus: Contains DNA and controls many cell activities.
Nuclear envelope: Double membrane surrounding the nucleus.
Nuclear pores: Openings that control movement into and out of the nucleus.
Nucleolus: Region of the nucleus where ribosomes are made.
Chromatin: DNA and proteins found inside the nucleus.
Chromosome: Condensed form of DNA containing genetic information.
Cell wall: Rigid outer layer that supports and protects certain cells.
Cellulose: Main material in plant cell walls.
Chitin: Strong material found in fungal cell walls and some animal structures.
Vacuole: Membrane-bound structure used for storage.
Turgor pressure: Pressure of water inside a plant cell pushing against the cell wall.
Plastid: Plant-cell organelle involved in storage or pigment production.
Photosynthesis: Process plants use to convert light energy into chemical energy.
Chloroplast: Plastid where photosynthesis occurs.
Leucoplast: Plastid that stores substances such as starch.
Chromoplast: Plastid containing pigments that give plants their colors.
Centriole: Structure involved in organizing microtubules during cell division.
Mitosis: Cell division producing two genetically identical cells.
Meiosis: Cell division producing sex cells with half the usual number of chromosomes.
Protein: Molecule made of amino acids that performs many cell functions.
Homeostasis: Maintaining a stable internal environment.
Phospholipid: Molecule with a hydrophilic head and hydrophobic tails.
Phosphate: Water-attracting part of a phospholipid head.
Glycerol: Molecule forming part of the structure of a phospholipid.
Fatty acids: Molecules forming the hydrophobic tails of phospholipids.
Lipids: Group of molecules including fats, oils, and phospholipids.
Carrier protein: Membrane protein that changes shape to move substances across the membrane.
Channel protein: Membrane protein that provides a passageway for specific substances.
Diffusion: Movement of particles from high concentration to low concentration.
Dynamic equilibrium: Particles continue moving, but concentrations remain relatively equal.
Concentration gradient: Difference in concentration between two areas.
Osmosis: Diffusion of water across a selectively permeable membrane.
Isotonic: Solution with equal solute concentration compared with the cell.
Hypotonic: Solution with lower solute concentration than the cell; water enters the cell.
Hypertonic: Solution with higher solute concentration than the cell; water leaves the cell.
Contractile vacuole: Structure that removes excess water from some cells.
Plasmolysis: Plant cell membrane pulls away from the cell wall because water leaves the cell.
Cytolysis: Cell bursts because too much water enters.
Passive transport: Movement across the membrane without using cellular energy.
Facilitated diffusion: Passive movement through channel or carrier proteins.
Active transport: Movement across the membrane using energy, usually against the concentration gradient.
Endocytosis: Cell takes materials in by forming a membrane vesicle.
Exocytosis: Cell releases materials when a vesicle fuses with the cell membrane.
Phagocytosis: “Cell eating”; taking in large particles or organisms.
Pinocytosis: “Cell drinking”; taking in fluids and dissolved substances.
Surface area: Total area of an object's outer surface.
Volume: Amount of space an object occupies.
Surface area-to-volume ratio: Surface area compared with volume.
Metabolic activity: Chemical reactions occurring inside an organism or cell.
OBJECTIVES
1. Cell theory: All living things are made of cells; cells are the basic unit of life; all cells come from pre-existing cells.
2. Cell theory scientists: Robert Hooke named cells; Anton van Leeuwenhoek observed living cells; Matthias Schleiden concluded plants are made of cells; Theodor Schwann concluded animals are made of cells; Rudolf Virchow stated cells come from existing cells.
3. Eukaryotic vs. prokaryotic: Eukaryotes have a nucleus and membrane-bound organelles; prokaryotes do not. Example eukaryote: animal cell. Example prokaryote: bacterium.
4. Organization: Cell → tissue → organ → organ system → organism. Example: muscle cell → muscle tissue → heart → circulatory system → human.
5. Organelles: Each organelle has a specialized function, such as the nucleus storing DNA, ribosomes making proteins, mitochondria producing ATP, and Golgi apparatus packaging materials.
6. Plant vs. animal cells: Both have a cell membrane, cytoplasm, nucleus, ribosomes, mitochondria, ER, Golgi apparatus, and other shared structures. Plants also have a cell wall, chloroplasts, and large central vacuole.
7. Cell diagrams: Know how to identify the cell membrane, cytoplasm, nucleus, nucleolus, ribosomes, ER, Golgi, mitochondria, lysosomes, cytoskeleton, cell wall, chloroplasts, and vacuole.
8. Membrane transport: The membrane regulates what enters and leaves through selective permeability and different transport mechanisms.
9. Protein production: DNA → mRNA → ribosome → rough ER → transport vesicle → Golgi apparatus → vesicle → destination. The nucleus provides the instructions, while ribosomes build the protein.
10. Mitochondria/cristae: Mitochondria produce ATP through cellular respiration. Cristae are folds that increase surface area for ATP-producing reactions.
11. Nucleus: Stores DNA and controls cell activities by regulating gene expression.
12. Turgor pressure: Water inside a plant cell pushes against the cell wall, helping the plant stay firm.
13. Homeostasis: Keeping internal conditions stable. Examples include regulating temperature, water balance, blood sugar, and pH.
14. Unstable internal environment: Can cause cells and enzymes to function poorly, potentially leading to cell damage or death.
15. Selective permeability/homeostasis: The membrane controls which substances enter and leave, helping maintain the cell's proper internal conditions.
16. Cell membrane: Hydrophilic heads → hydrophobic tails → hydrophobic tails → hydrophilic heads. Proteins are embedded throughout the bilayer.
17. Phospholipid: Phosphate + glycerol = hydrophilic head; fatty acids = hydrophobic tails.
18. Water attraction: Hydrophilic heads face the watery environments inside and outside the cell, while hydrophobic tails face inward away from water.
19. Fluid mosaic: The membrane is fluid because phospholipids can move, and a mosaic because it contains many different proteins and molecules.
20. Diffusion: Particles move from high concentration → low concentration. Example: oxygen moving into a cell.
21. Dynamic equilibrium: Particles continue moving in both directions, but there is no overall change in concentration.
22. Osmosis: Movement of water across a selectively permeable membrane from an area of higher water concentration to lower water concentration.
23. Diffusion vs. osmosis: Both are passive transport and move substances down a concentration gradient. Diffusion applies to particles generally; osmosis specifically involves water.
24. Tonicity: Isotonic: equal solute, no net water movement. Hypotonic: lower solute outside, water enters. Hypertonic: higher solute outside, water leaves.
25. Hypotonic/hypertonic consequences: Hypotonic solutions can cause animal cells to swell or burst. Hypertonic solutions cause cells to shrink; plant cells can undergo plasmolysis.
26. Passive vs. active transport: Passive transport requires no energy and moves down the gradient. Active transport requires energy and can move substances against the gradient.
27. Endocytosis/exocytosis: Endocytosis brings materials into the cell; exocytosis releases materials out of the cell.
28. Phagocytosis vs. pinocytosis: Phagocytosis = cell eating, taking in large particles. Pinocytosis = cell drinking, taking in fluids.
29. Small cells: Small cells have a higher surface area-to-volume ratio, allowing materials to enter and leave more efficiently.
30. Surface area/volume: Cube SA = 6 × side²; cube V = side³; SA:V = surface area ÷ volume.
31. Improving SA:V ratio: Cells can stay small, become long/thin, develop folds, or have structures that increase surface area without greatly increasing volume.