Honors Biology – Complete Study Guide

This combines your original study guide, your teacher’s additional study sheet, and the fish/osmoregulation explanations into one organized guide.

1. Prokaryotic vs. Eukaryotic Cells

Prokaryotic Cells

Eukaryotic Cells

No nucleus

Have a nucleus

No membrane-bound organelles

Have membrane-bound organelles

Smaller and simpler

Larger and more complex

Example: bacteria

Examples: plants and animals

Remember: Prokaryotes have no nucleus; eukaryotes do.

2. Plant vs. Animal Cells

Plant cells:

  • Have a cell wall for support and protection.

  • Have chloroplasts for photosynthesis.

  • Have a large central vacuole for storing water and other materials.

  • Usually have a more rigid shape.

Animal cells:

  • Do not have a cell wall or chloroplasts.

  • Usually have smaller vacuoles.

  • Have lysosomes that help break down waste.

  • Usually have a more flexible shape.

3. Cell Organelles and Their Functions

Organelle

Function

Nucleus

Controls cell activities and stores DNA

Cell membrane

Controls what enters and leaves the cell

Cytoplasm

Jelly-like material where organelles are found

Mitochondria

Produce ATP energy

Ribosomes

Make proteins

Rough ER

Helps make and transport proteins

Smooth ER

Makes lipids and helps detoxify substances

Golgi apparatus

Modifies, packages, and ships proteins

Lysosomes

Break down waste and old cell parts

Vacuole

Stores water, food, and waste

Chloroplasts

Perform photosynthesis in plants

Cell wall

Provides support and protection

Cytoskeleton

Helps maintain cell shape and movement

4. Cell Membrane

The cell membrane controls what enters and leaves the cell.

  • Phospholipid bilayer: Two layers of phospholipids that make up the membrane.

  • Hydrophilic: Water-loving heads that face the watery environments.

  • Hydrophobic: Water-fearing tails that face inward.

  • Proteins: Help move substances across the membrane.

  • Cholesterol: Helps maintain membrane stability and fluidity.

  • Carbohydrates: Help cells recognize and communicate with one another.

  • Fluid mosaic model: Describes the membrane as flexible, with different molecules moving around within it.

5. Passive Transport

Passive transport does not require ATP energy. Substances move from an area of high concentration to low concentration.

  • Diffusion: Movement of molecules from high to low concentration.

  • Osmosis: Diffusion of water across a selectively permeable membrane.

  • Facilitated diffusion: Substances move from high to low concentration through membrane proteins.

Remember: Passive transport = no energy required.

6. Active Transport

Active transport requires ATP energy to move substances, often from low to high concentration.

  • Protein pumps: Move substances across the membrane using energy.

  • Endocytosis: Cell brings materials into itself using a vesicle.

  • Exocytosis: Cell releases materials outside itself using a vesicle.

  • Phagocytosis: A type of endocytosis where a cell takes in large particles.

Remember: Active transport = energy required.

7. Hypertonic, Hypotonic, and Isotonic Solutions

These terms describe the concentration of dissolved substances outside a cell compared with inside.

Hypertonic

  • More solute outside the cell.

  • Water moves OUT of the cell.

  • Cell shrinks.

Hypotonic

  • Less solute outside the cell.

  • Water moves INTO the cell.

  • Cell swells.

Isotonic

  • Equal solute concentration inside and outside.

  • Water moves in and out equally.

  • Cell stays about the same size.

Memory trick:

  • Hypertonic = water leaves.

  • Hypotonic = water enters.

  • Isotonic = balanced.

8. Microscopes

  • Coarse adjustment knob: Moves the stage or lens significantly to get general focus. Best used on low power.

  • Fine adjustment knob: Makes small adjustments to sharpen the image. Especially important on high power.

Remember: Coarse = big adjustments; fine = small adjustments.

9. Endosymbiotic Theory

The endosymbiotic theory explains how mitochondria and chloroplasts may have originated from ancient bacteria that were engulfed by larger cells.

Evidence includes:

  • Mitochondria and chloroplasts have their own DNA.

  • They have their own ribosomes.

  • They reproduce independently through a process similar to binary fission.

  • They have double membranes.

Remember: Mitochondria and chloroplasts have evidence of once being independent organisms.

10. Levels of Organization

From smallest to largest:

Cell

Tissue

Organ

Organ System

Organism

  • Cell: Basic unit of life.

  • Tissue: Group of similar cells working together.

  • Organ: Group of tissues working together.

  • Organ system: Group of organs working together.

  • Organism: A complete living thing.

11. Major Body Systems

Body System

Main Function

Nervous

Sends signals and controls body responses

Circulatory

Moves blood, oxygen, and nutrients

Respiratory

Brings in oxygen and removes carbon dioxide

Digestive

Breaks down food and absorbs nutrients

Muscular

Allows movement

Skeletal

Supports and protects the body

Integumentary

Skin, hair, and nails; protects the body

Urinary/Excretory

Removes waste and regulates water balance

Endocrine

Uses hormones to regulate body functions

Immune

Protects against pathogens

Reproductive

Allows organisms to produce offspring

12. Sodium-Potassium Pump

The sodium-potassium pump is an example of active transport.

  • Uses ATP energy.

  • Moves 3 sodium ions (Na⁺) OUT of the cell.

  • Moves 2 potassium ions (K⁺) IN to the cell.

  • Helps maintain electrical differences across cell membranes.

  • Important for nerve and muscle function.

Memory trick: 3 OUT, 2 IN.

13. Osmosis and Fish

This is an important topic because freshwater and saltwater fish must keep their water and salt levels balanced.

Osmosis: Water moves across a selectively permeable membrane toward the side with a higher solute concentration.

Freshwater fish

  • Freshwater has less salt than the fish’s body.

  • Water moves INTO the fish through osmosis.

  • The fish produces lots of dilute urine to remove extra water.

  • It actively takes in salts through its gills.

  • It must keep salt inside its body.

Key idea: Freshwater fish gain water and lose salt.

Saltwater fish

  • Saltwater has more salt than the fish’s body.

  • Water moves OUT of the fish through osmosis.

  • The fish drinks seawater to replace lost water.

  • Its gills remove excess salt.

  • It produces less urine to conserve water.

Key idea: Saltwater fish lose water and gain salt.

Freshwater vs. Saltwater Fish

Freshwater Fish

Saltwater Fish

Water moves in

Water moves out

Produces lots of dilute urine

Produces less urine

Takes in salt through gills

Removes excess salt through gills

Gains water

Loses water

Does not need to drink much

Drinks seawater

Salmon Migration

Salmon move between freshwater and saltwater during their life cycle.

  • Salmon hatch in freshwater.

  • They grow and eventually migrate to the ocean.

  • They adjust how their gills and kidneys regulate salt and water.

  • They mature in saltwater.

  • They return to freshwater to reproduce.

  • Their bodies adjust again to the new environment.

Remember: Salmon must change how they regulate water and salt when moving between freshwater and saltwater.

14. Homeostasis

Homeostasis is maintaining a stable internal environment even when the outside environment changes.

Examples:

  • Maintaining body temperature.

  • Keeping blood sugar levels stable.

  • Regulating water and salt levels.

  • Maintaining proper oxygen and carbon dioxide levels.

Negative Feedback

Negative feedback reverses a change to bring the body back toward normal.

Example: Body temperature

  • If body temperature gets too high, sweating helps cool the body.

  • If body temperature gets too low, shivering helps warm the body.

Blood Sugar Regulation

  • Insulin: Lowers blood glucose levels.

  • Glucagon: Raises blood glucose levels.

Memory trick: Insulin brings sugar down; glucagon brings sugar up.

15. Photosynthesis and Cellular Respiration

Photosynthesis

  • Happens in chloroplasts.

  • Uses sunlight, water, and carbon dioxide.

  • Produces glucose and oxygen.

  • Allows plants to store energy in glucose.

Cellular respiration

  • Mostly happens in mitochondria.

  • Breaks down glucose to make ATP.

  • Uses oxygen during aerobic respiration.

  • Produces carbon dioxide and water.

Photosynthesis

Cellular Respiration

Stores energy in glucose

Releases energy to make ATP

Uses CO₂ and water

Uses glucose and oxygen

Produces glucose and oxygen

Produces CO₂ and water

Aerobic vs. Anaerobic Respiration

  • Aerobic: Uses oxygen and produces much more ATP.

  • Anaerobic: Does not require oxygen and produces much less ATP.

16. ATP and Enzymes

ATP

  • Stands for adenosine triphosphate.

  • Main usable energy source for cells.

  • Powers processes such as active transport and muscle contraction.

Enzymes

  • Proteins that speed up chemical reactions.

  • Lower the activation energy needed for reactions.

  • Are not used up during the reaction.

  • Can be affected by temperature and pH.

  • Have specific substrates they work with.

17. Cell Communication

Cells communicate to coordinate their activities.

  • Cell signaling: Cells send and receive messages.

  • Gap junctions: Channels that allow communication between animal cells.

  • Plasmodesmata: Channels that connect plant cells.

  • Receptors: Proteins that receive signals.

Remember:

  • Gap junctions = animal cells.

  • Plasmodesmata = plant cells.

18. Gas Exchange

Gas exchange occurs in the alveoli, tiny air sacs in the lungs.

  • Oxygen moves from the alveoli into the blood.

  • Carbon dioxide moves from the blood into the alveoli.

  • Carbon dioxide is then breathed out.

Most Important Things to Memorize

These are especially worth reviewing before your test:

  • Prokaryotic cells have no nucleus; eukaryotic cells do.

  • Mitochondria produce ATP.

  • Ribosomes make proteins.

  • Chloroplasts perform photosynthesis.

  • The cell membrane controls what enters and leaves.

  • Diffusion is movement of molecules; osmosis is movement of water.

  • Passive transport requires no energy.

  • Active transport requires ATP.

  • Hypertonic = water leaves; hypotonic = water enters; isotonic = balanced.

  • Coarse adjustment = large focus changes; fine adjustment = small changes.

  • Endosymbiotic theory explains the origins of mitochondria and chloroplasts.

  • Cell → tissue → organ → organ system → organism.

  • Sodium-potassium pump = 3 Na⁺ out, 2 K⁺ in.

  • Freshwater fish gain water; saltwater fish lose water.

  • Salmon adjust their osmoregulation when migrating.

  • Insulin lowers blood sugar; glucagon raises it.

  • Homeostasis means maintaining stable internal conditions.

  • Gap junctions = animals; plasmodesmata = plants.

  • Photosynthesis stores energy; cellular respiration makes ATP available.

  • Alveoli exchange oxygen and carbon dioxide.

Study tip: Focus especially on osmosis, fish, active vs. passive transport, organelle functions, and the sodium-potassium pump. Those topics involve concepts you need to understand, not just memorize.