The Plant Cell Chapter 2 Robert Hooke a

The Plant Cell Chapter 2

Robert Hooke, a 17 th c. British physicist, first used the term “cell’ to describe the units he observed in a sliver of corky bark.

Schleiden Virchow Schwann Weismann The German biologists Schleiden and Schwann proposed in the 1830 s that: • cells are the structural units of life • all cells come from pre-existing cells via cell division. This idea has come to be known as the Cell Theory.

How big is a plant cell?

Comparison of Prokaryotic and Eukaryotic Cells • Prokaryotic cells: • Eukaryotic cells: • e. g. , bacteria • Relatively simple structure • Lack nucleus and other membranebound organelles • ca. 1 - 10 um diam. • e. g. , plant & animal cells • Nucleus and other membrane-bound organelles present • ca. 100 um diam.

Basic features of all cells 1. Plasma membranes – a selective barrier made of lipids and proteins 2. Cytoplasm – a jellylike fluid containing all organelles and other components 3. Chromosomes - carry genes in the form of DNA, duplicate before cell division 4. Ribosomes – small complexes of proteins and RNA molecules that are sites of protein assembly

The Geography of the Plant Cell

Plant Cell Structure I. Cell Wall II. Protoplast A. Plasma Membrane B. Cytoplasm 1. Cytosol 2. Nucleus 3. Organelles a. Chloroplasts b. Mitochondria c. Ribosomes C. Vacuole

Palisade parenchyma Spongy parenchyma

protoplast plasma membrane

All plant cells are contained by a cell wall http: //www. bio. miami. edu cell wall – the outer layer of a plant cell consisting of various carbohydrates (e. g. , cellulose, pectin, lignin) • primary cell wall is thin and flexible • secondary cell wall is stiff (lignin) and waterproof (suberin)

Glucose molecule

The plasma membrane creates a selective barrier Lipid bilayer Protein selective barrier the solution inside the cell differs from the solution outside the cell

Osmosis - the passive movement of water across a plasma membrane Direction of water movement: high concentration low concentration http: //weknowmemes. com

O O Osmosis (passive water movement) in plant cells Lys Norm Shrivele H 2 O ed Turgid (normal) H 2 O al Flaccid H 2 O Plasmolyzed

up to 90% of the cell volume plasma membrane

plasma membrane

Nucleus = the cell’s “information center” The nucleus contains chromosomes - long strands of DNA that contain genes nucleus http: //mimp. mems. cmu. edu

Chromosomes in a dividing onion root tip

Cell division produces 2 identical cells A dividing cell (chromosomes containing DNA are labeled blue)

The cell duplicates its chromosomes and divides them equally into 2 new cells during mitosis Chromosomes DNA molecules Replicated chromosome http: //www. youtube. com/watch? v=4 gov. Zdj. EBrs

Plant Cell Structure: The Geography of the Cell I. Cell Wall II. Protoplast A. Plasma Membrane B. Cytoplasm 1. Cytosol 2. Nucleus 3. Organelles a. Ribosomes b. Mitochondria c. Chloroplasts C. Vacuole

Ribosomes The Plant Cell

Ribosomes are sites of protein assembly A ribosome is a molecule consisting of RNA and proteins. RNA © Tom Pantages proteins (pink and purple)

Many proteins are processed and shipped after leaving the ribosome Endoplasmic reticulum – protein processing Golgi apparatus – the “warehouse; ” proteins are shipped to their final destination Nucleus Endoplasmic Reticulum Ribosomes Endoplasmic Reticulum

Connections within a cell Nucleus Rough ER Golgi Plasma membrane

Energy Transducers: Mitochondria and Chloroplasts

Chloroplast Structure

Chloroplast Structure

The Cellular ‘Metropolis’ with ribosomes

Good summary table (focus on cell structures discussed in lecture)

Lecture Review, Chapter 2 • • What are the 4 basic features of all living cells? What are the major tenets of the cell theory? Compare and contrast prokaryotic and eukaryotic cells. Describe the structure and function of the cell wall and plasma membrane. • Define organelle, and be able to label the organelles in a plant cell. • Define osmosis. Which is the most ideal for a plant cell: water moving into the cell, water moving out of the cell, or water moving at equal rates into and out of a cell? • Define mitosis. What is the direct result of 1 round of mitosis in a plant?