Plant Cells

Plasma Membrane

  • barrier that separates inside of cell from environment

  • phospholipid bilayer

  • selectively permeable

Protein Receptors: use signal transduction to relay

Transport Proteins:

  • Channel proteins: form little tunnels in membrane to allow small molecules to pass quickly

  • Carrier Proteins: pick a molecule up on one side of the membrane and alter their shape to deposit it on the other side

Protoplast: everything inside cell minus nucleus and cell wall

Ribosomes

  • small structures in cells that help build proteins

  • made of Ribosomal RNA (rRNA) and proteins

  • rRNA and proteins are twisted together to form large and small subunits

  • come together to form a completed ribosome when the cell begins to make a protein

Protein Production

  • Transcription: mRNA reads DNA in nucleus, carries instructions to ribosome

  • Translation: ribosomes organize mRNA and other molecules needed to build proteins and assemble

Some organelles are only specific to plants: cell wall, plastids (incl. chloroplasts), large central vacuole, and plasmodesmata

Endomembrane System

  • Large network of membranes that helps construct proteins/lipids, package them, and sends them to the target destination

Endoplasmic Reticulum: set of folded membranes that begins at nucleus and extends into cytoplasm

Rough ER: studded with ribosomes that begin to make the protein then attach the proteins to the ER. After synthesis, the protein is packed by vesicles and sent to golgi apparatus.

Smooth ER: no attached ribosomes; produce lipids

Golgi Apparatus/Dictyosomes: stack of flattened membrane sacs

Vesicles

  • little sphere of membrane

  • Transport Vesicles: carry things around the cell

  • Lysosomes: contain digestive enzymes that break down molecules, organelles, and bacterial cells

  • Secretory Vesicles: bring materials to plasma membrane so they can be secreted by the cell

Peroxisomes

  • small organelles encircled by single membrane

  • break down lipids

Vacuoles

  • spheres of membrane differing from vesicles

  • used to dump wastes and store materials

  • up to 95% of cell volume

  • separated by membrane called tonoplast

Cytoskeleton

network of protein cables that function as:

  • Scaffolding: underlie membranes to provide shape and support

  • Movement of materials by vesicles and organelles along protein tracks

  • Movement of cells when found within the cilia and flagella

3 Types:

  1. Microfilaments: made of protein Actin

  • involved in cell division, expansion, railroad tracks of vesicles/organelles

  • aid in cytoplasmic streaming (circulation)

  • help pinch cells in two during cell division

  1. Microtubules: made of protein Tubulin

  • move chromosomes during cell division

  • railroad tracks

  • help organic formation of cell wall and determine the development of plant shape

  1. Intermediate Filaments: made of various proteins to reinforce cellular structures

Chloroplasts

  • contain chlorophyll

  • green compartment organelle where photosynthesis occurs

Thylakoid: little stacks of fluid-filled membranes

Stroma: fluid-filled interior

Granum: stack of thylakoids

Plastid: self-replicating organelles that are surrounded by double membrane and perform important chemical processes in plant cells

Types:

  1. Proplastids (Eoplastids): small, colorless plastids that give rise to all types of plastids; found in seedlings and plant tissues that are unspecialized

  2. Leucoplastids: colorless plastids that specialize in the synthesis and storage of important molecules

  • Amyloplastids: make and store starch. Found in roots and other starch storage tissues.

  • Elaioplasts (Oleoplasts): make and store oil. Found in tissues that provide support to developing pollen grains.

  • Proteinoplasts/proteoplasts/aleuroplasts: make and store proteins. Found in many seeds

  1. Chromoplasts: red, orange, yellow that contain carotenoids. Found in flowers, fruit and leaves that are turning in the fall. They can be formed from chloroplasts, amyloplasts and proplastids.

  2. Etioplasts: pale, yellowish plastids found in plant tissues growing in the dark. Develop into chloroplasts when exposed to light.

Mitochondria

  • site of cellular respiration where energy is released from food

  • double membrane

  • Intermembrane space: between the two membranes of the mitochondrion

  • Matrix: fluid-filled space inside inner membrane

Cell Walls and Extracellular Matrices

  • additional layers outside of plasma membrane that provide additional strength to cells and may attach cells together

  • Cell Walls: semi-rigid reinforcing layers that protect the cell

  • Extracellular Matrix (ECM): flexible layer formed around animal cells; made of long proteins (collagen) embedded in polysaccharide gel

  • plants form cell wall outside in

  • Plasmodesmata: little tunnels that pass through cell walls

Layers

  1. Middle Lamella:

  • outermost layer that helps stick plant cells together

  • forms first when plants divide

  • thin, flexible layer made of sticky polysaccharides (pectin)

  1. Primary Cell Wall: formed under middle lamella during and before active growth (cellulose)

  2. Secondary Cell Wall: woody plants (lignin and cellulose)

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