3.6 Plant Cell Structures

Learning Objectives

• Distinguish plant cells from animal cells.

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Introduction

Do plants have cells like you have?

Yes, your cells are actually very similar to a plant's cells. For example, they are both eukaryotic cells, both contain DNA in a nucleus, and both make proteins in ribosomes. However, plant cells also differ in some crucial ways from your own cells.

Guided Learning

Plant Cells

Even though plants and animals are both eukaryotes, plant cells differ in some ways from animal cells (Figure below). Plant cells have a large central vacuole, are surrounded by a cell wall, and have chloroplasts, which are the organelles of photosynthesis.

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A plant cell has several features that make it different from an animal cell, including a cell wall, huge vacuoles, and chloroplasts, which photosynthesize.

Vacuoles

First, plant cells have a large central vacuole that holds a mixture of water, nutrients, and wastes. A plant cell's vacuole can make up 90% of the cell’s volume. The large central vacuole essentially stores water. What happens when a plant does not get enough water? In animal cells, vacuoles are much smaller.

Cell Wall

Second, plant cells have a cell wall, while animal cells do not (Figure below). The cell wall surrounds the plasma membrane but does not keep substances from entering or leaving the cell. A cell wall gives the plant cell strength and protection.

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In this photo of plant cells taken with a light microscope, you can see green chloroplasts as well as a cell wall (blue-green border) around each cell.

Plastids

A third difference between plant and animal cells is that plants have several kinds of organelles called plastids. And there are several different kinds of plastids in plant cells. For example, Chloroplasts are needed for photosynthesis, leucoplasts can store starch or oil, and brightly colored chromoplasts give some flowers and fruits their yellow, orange, or red color. It is the presence of chloroplasts and the ability to photosynthesize, that is one of the defining features of a plant. No animal or fungi can photosynthesize, and only some protists are able to. The photosynthetic protists are the plantlike protists, represented mainly by the unicellular algae.

Review

• Plant and animal cells differ in that plants have a large central vacuole, while animals have smaller vacuoles.
• Plant cells also have cell walls and plastids, while animal cells do not.

Vocabulary

cell wall

Tough outer layer of plant cells that helps support and protect the cell; also found around bacterial cells.

chloroplast

Organelle that carries out photosynthesis in plants.

photosynthesis

Process by which specific organisms (including all plants) use the sun's energy to make their own food from carbon dioxide and water; process that converts the energy of the sun, or solar energy, into carbohydrates, a type of chemical energy.

plastid

Small membrane-bound organelle of plant cells with varying functions.

vacuole

Membrane-bound space within the cell used for storage of water, wastes, and nutrients.