Biology Chapter: Plant and Animal Cells

Cell Theory and Organelles

• All living things are made of cells
• Cells are the basic unit of life
• All cells come from other cells
• Organisms can be unicellular (one cell) or multicellular (many cells that organize into tissues, organs, and organ systems).
• Cells are the smallest part of an organism that can still perform all functions of life.
• Cells are diverse.
• Two main types of cells: prokaryotic and eukaryotic
• Prokaryotic cells do not have a nucleus or membrane-bound organelles.
• Eukaryotic cells have a nucleus and membrane-bound organelles.
• Prokaryotic cells reproduce by binary fission.
• Eukaryotic cells reproduce by mitosis.
• Prokaryotic organisms tend to be unicellular.
• Eukaryotic organisms can be unicellular or multicellular.
• Examples of organisms with prokaryotic cells are bacteria.
• Examples of organisms with eukaryotic cells include animals, plants, fungi, and protists.
• All cells have genetic material (DNA/RNA), cytoplasm, a cell membrane, and ribosomes.
• Organelles are specialized structures that work together within the cell to help the cell function. Think of them as "mini organs" within the cell working together to make proteins!
• Eukaryotic cells have specialized membrane-bound organelles.

Cell Membrane

• Surrounds all cells
• Made of a phospholipid bilayer
• Controls what goes in and out of the cell (material exchange)
• Critical for communication and maintaining a stable internal environment (homeostasis)
• Consists of two layers of phospholipid molecules:
  • Hydrophilic heads (like water): face outwards toward the environment and cytoplasm
  • Hydrophobic tails (dislike water): face inwards, away from the environment and cytoplasm.
• Contains proteins embedded for transport, and carbs embedded for structure.
• Called "fluid mosaic model" because it composed of many parts that move around freely.
• Contains cholesterol that helps membrane remain flexible.

Cytoskeleton

• Threadlike fibers made of proteins
• Usually not pictured in cell diagrams.
• Provides cells with shape
• Can move organelles around
• Provides structural support for animal cells

Cytoplasm

• Jelly-like substance
• Mainly composed of water
• Holds everything in place within the cell
• Provides a solution for chemical reactions to take place within the cell.

Nucleus

• Contains genetic material (DNA)
• When DNA is spread out it is called chromatin
• When DNA is condensed it is called chromosomes.
• Surrounded by a nuclear envelope/membrane with pores that control what goes in and out of the nucleus.
• Protects the DNA that controls the activities of the cell

Nucleolus

• Inside the nucleus
• Makes rRNA which makes up ribosomes

Ribosomes

• Made of proteins and rRNA
• Located on rough ER and floating in the cytoplasm
• Make proteins in a process called translation
• Ribosomes on Rough ER make proteins to export out of the cell.
• Ribosomes floating in cytoplasm make proteins used within the cell.

Rough ER (Endoplasmic Reticulum)

• Has ribosomes on its surface
• Hugs the nucleus
• Makes proteins
• Packages proteins for secretion and sends them in vesicles to the Golgi.

Smooth ER (Endoplasmic Reticulum)

• No ribosomes on its surface.
• Attached to rough ER.
• Makes lipids (membrane)
• Stores Ca²⁺.

Golgi Apparatus

• Folded membrane
• Gets vesicles of protein from the ER
• Vesicles are like mini-carts that transport proteins around the cell.
• Processes, sorts, and ships proteins where needed

Lysosomes

• Contain enzymes
• Only in animal cells
• Break down dead stuff (food, bacteria, etc.) or old parts of cells.
• Can do programmed cell death (apoptosis).

Vacuoles

• Small and numerous in animal cells
• Plant cells has a one large central vacuole.
• Storage (water, nutrients, waste, etc.)

Centrioles

• Made of microtubules
• 2 centrioles together = centrosome
• Only in animal cells
• Appear during cell division
• Help in cell division by pulling chromosomes apart.

Cilia and Flagella

• Organelles associated with the cytoskeleton
• Cilia: shorter, more numerous, like tiny oars (move fluid across cell's surface).
• Flagella: longer, fewer (1-3), move entire cell through extracellular fluid (animal and bacteria only)

Mitochondria

• Two parts: inner membrane and matrix (fluid part)
• Where cellular respiration happens
• C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + energy (ATP)
• Breaks down chemical energy in food to release usable energy in the form of ATP.

Chloroplasts

• Two parts: grana (stacks) and stroma (fluid)
• Only in plant cells
• Where photosynthesis happens.
• Converts light energy from the sun to chemical energy in sugar.
• 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂

Cell Wall

• Only in plant cells, bacteria, and fungi cells
• Made of cellulose (in plants), chitin (in fungi) and peptidoglycan (in bacteria).
• Protects and maintains shape.

Central Vacuole

• Only in plant cells
• One massive central structure
• Storage center