Plant Cells

• Biological organization starts with atoms, which combine to form molecules
• Molecules make up cells, the basic unit of life
• Similar cells form tissues, which create organs
• Multiple organs work together in organ systems to sustain a complete organism

Structure of a Plant Cell

• Plant cells include organelles like the cell wall, plasma membrane, cytoplasm, nucleus, vacuole, chloroplasts, mitochondria, Golgi apparatus, endoplasmic reticulum, ribosomes, peroxisomes, and plasmodesmata
• The cell wall provides structural support and protection
• The plasma membrane regulates the entry and exit of substances
• The cytoplasm contains organelles and cellular components
• The nucleus contains DNA and controls cell activities
• The nuclear envelope surrounds and protects the nucleus
• The nucleolus produces ribosomes
• Vacuoles store nutrients, water, and waste
• Chloroplasts perform photosynthesis
• Mitochondria generate energy (ATP)
• The Golgi apparatus packages and transports proteins
• The rough ER has ribosomes and aids in protein synthesis
• The smooth ER lacks ribosomes and synthesizes lipids
• Ribosomes produce proteins
• Peroxisomes break down harmful substances
• Plasmodesmata are channels for communication between plant cells
• A eukaryotic plant cell includes a cell wall for structural integrity
• The plasma membrane provides selective permeability, and the cytoplasm holds organelles
• The nucleus controls genetic material, and the vacuole is for central storage and waste disposal
• Chloroplasts conduct photosynthesis, and mitochondria generate energy
• The endoplasmic reticulum (rough and smooth) synthesizes proteins and lipids
• The Golgi apparatus modifies and transports proteins
• Ribosomes are protein factories, and peroxisomes perform detoxification
• Microtubules shape and transport the cell
• The middle lamella holds adjacent cells together

Introduction to Cells

• Cells are the structural and functional units of living organisms
• Robert Hooke first observed plant cells
• Robert Brown first observed the nucleus of cells
• Matthias Schleiden stated plants are composed of cells
• Theodor Schwann stated animals are composed of cells
• The bodies of plants and animals consist of cells and their products
• Cells originate from pre-existing cells

Fundamental Types of Cells

• Prokaryotic cells lack a nucleus and are simple/primitive
• They lack some organelles and exist independently as single-celled organisms (e.g., bacteria, algae)
• Eukaryotic cells have a nucleus and complex organelles
• They are found in multicellular organisms like plants, animals, and humans

Plant Cell Specializations

• Cells of shoot/root tips are for cell division and protoplasm production
• Epidermis cells retain water and act as barriers against fungi and insects
• Epidermal gland cells protect and produce poisons against herbivores
• Green leaf cells collect solar energy for photosynthesis
• Root epidermal cells collect water and minerals from soil
• Vascular cells transport water, minerals, and organic molecules
• Flower cells have functions related to reproduction and pollination
• Petal cells contain pigments to attract pollinators
• Scent cells produce fragrances to attract pollinators
• Nectary cells produce sugars to attract pollinators
• Stamen cells are indirectly involved in sperm cell production
• Carpel cells are indirectly involved in egg cell production
• Fruit cells produce sugars, aromas, and flavors to attract seed-dispersing animals

Plant Cell Parts

• The cell wall provides structural support and protection
• The protoplasm includes the plasma membrane, nucleus, and cytoplasm
• The plasma membrane regulates material exchange
• The nucleus controls cell activities and contains DNA
• The cytoplasm includes cytosol and organelles
• Cytosol is the semi-fluid matrix where organelles are suspended
• Organelles include mitochondria for ATP production and plastids (chloroplasts, chromoplasts, leucoplasts)
• Chloroplasts contain chlorophyll for photosynthesis
• Chromoplasts contain pigments for fruit and flower color
• Amyloplasts store starch
• Proteinoplasts store proteins
• Elaioplasts store lipids
• The endoplasmic reticulum (ER) is involved in protein synthesis (rough ER) and lipid synthesis/detoxification (smooth ER)
• Ribosomes synthesize proteins

Other parts of the cell

• Dictyosomes (Golgi Apparatus) modify, sort, and package proteins and lipids
• Microbodies include peroxisomes, which break down hydrogen peroxide and fatty acids, and glyoxysomes, which convert stored lipids into carbohydrates during germination
• The cytoskeleton provides structural support and aids in cell movement
• Vacuoles store water, nutrients, and waste and maintain turgor pressure
• The cell wall provides protection and structural support
• It's made of carbohydrates (cellulose).
• Cell walls are present in all cells except animal cells
• Cell walls help with the structural support, defense, communication and other actions, like cellular functions

Cell structural components

• Cellulose is the primary component, forming strong fibers
• Hemicellulose acts as glue, holding cellulose fibers together
• Pectin adds stiffness and is known for its role in fruit jellies
• Proteins are involved in cell wall functions, including signaling and repair

Cell Wall Layers

• The cell wall is a non-living, rigid covering that is porous and somewhat elastic
• It has three main layers: the middle lamella, primary wall, and secondary wall
• The middle lamella (intercellular layer) is made of pectin, which cements adjacent cells together and contains cellulose fibers
• The primary wall is secreted against the middle lamella and contains cellulose and cutin (forms the cuticle), which protects against water loss
• The secondary wall is found inside the primary wall in cells with thick walls and contains cellulose, lignin (for hardness and decay resistance), and suberin (for impermeability to water and gas)
• Pits allow diffusion of water and other substances where no secondary wall is deposited
• Plasmodesmata are pores that connect adjacent cells for material and impulse transfer
• Protoplasm is the living material of the cell surrounded by the non-living cell wall
• The cell membrane (plasmalemma/plasma membrane) is made of phospholipids, proteins, and carbohydrates
• It acts as a semi-fluid boundary that controls the passage of substances in and out of the cell
• It is impermeable to harmful substances.
• It is made of two layers of phospholipids with embedded proteins

Properties of a Cell

• The outer boundary of the living part of the cell regulates what enters and leaves and is key for cellulose production and assembly for cell walls
• The plasma membrane's chemical composition is crucial in the transport process
• Transmembrane movement:
• Impermeable membranes allow nothing to pass through
• Freely permeable membranes allow anything to pass through
• Selectively permeable membranes allow certain substances to pass through quickly and others slowly
• Facilitated diffusion involves large intrinsic membrane proteins for hydrophilic, charged molecules
• Active transport uses large intrinsic membrane proteins to bind and force a molecule through the membrane while consuming energy
• Exocytosis: Vesicle fusion with the cell membrane releasing the contents
• Endocytosis: The invagination of the cell membrane, forming a vesicle

Nucleus & Cytoplasm

• The nucleus stores genetic information as chromosomes and serves as a permanent storage place
• It contains the genome, nuclear pores for passage between the nucleus and cytoplasm, and is a spherical organelle
• Nuclear Envelope includes two membranes and nuclear pores that allow material exchange between the nucleus and cytoplasm
• Nucleoplasm is the substance within the nucleus
• It is made of DNA (genetic material), enzymes and histone proteins and several types of RNA
• Nucleolus is the region responsible for ribosome production, that are involved in protein synthesis
• Cytoplasm contains dissolved substances:
• Cytosol/Hyaloplasm is a clear substance made of water and enzymes
• Cytoplasm is a rich "soup" of carbohydrates, proteins, fats, and nucleic acids
• Often referred to as protoplasm, that is a Watery or gelatin-like substance where all organelles are suspended

Mitochondria

• Mitochondria are double-layered outer membrane, energy-producing organelles
• It is the site of aerobic respiration, where energy (ATP) is generated for the cell
• It is responsible for energy generation and converts sugars to energy (ATP)
• The mitochondrion has its own genome
• The matrix contains enzymes and other molecules for cellular respiration
• They have their own DNA and ribosomes and dynamic organelles