Carbohydrate Structure and Plants I. Importance of carbohydrates to living things : 1. Carbohydrates – compounds made up of carbon, hydrogen, & oxygen atoms, usually in a ratio of 1 :2 :1, ex : sugars, starches, & cellulose. **Living things use carbohydrates as their main source of energy.** -Energy for cell activities comes from the immediate break-down of sugars, such as glucose. -Extra sugar is stored as complex carbohydrates known as starches.
3 Major Types of Carbohydrates Monosaccharides – single sugar molecules, ex : glucose (tissues), galactose (milk), & fructose (fruit). Disaccharides – double sugar molecules. Polysaccharides – large macromolecules formed from many sugars, ex : glycogen (animal starch), plant starch, & cellulose.
Plants (Kingdom Plantae) II. Introduction to Plants Plant – multicellular eukaryote that has a cell wall made of cellulose. -Plants perform photosynthesis using the green pigments chlorophyll a & b.
A. Characteristics of plants All plants : a. Are multicellular & don’t move. b. Are autotrophic – photosynthetic. c. Have cell walls made of a polysaccharide called cellulose. d. Have chloroplasts in their cells. e. Have alternation of generations – life cycles that alternate between a diploid (2N) & haploid (N) phase.
B. Size in plants *Size in plants depends on whether or not it has vascular tissue (xylem & phloem) to transport food, water, etc. Vascular tissue = larger plants. No vascular tissue = smaller plants.
III. Plant Structure & Function A. Specialized Structures in Plants -There are 3 principal organs of seed plants : 1. Leaves – are the major site of photosynthesis in plants. -Have 3 main parts : a. Blade – broad, flat photosynthetic surface of a leaf. b. Veins- vascular bundle that transports water & food in a leaf. c. Petiole – stalk that connects a leaf to a stem
Stems 2. Stems – have 3 main functions : a. Support leaves and flowers. b. Transport water/nutrients in plant. c. Storage (potato & starch) Stem Woodiness Woody stem – composed of cellulose, layers of xylem, lignin, and pectic substances. Produce bark. Herbaceous stem – fleshy stems that don’t produce bark as they grow.
Monocot vs. Dicot Stems
There are 4 main types of stems : a. Herbaceous plant – a non-woody plant composed of a relatively soft green tissue covered with a thin protective layer. b. Shrub – hard, strong stems. c. Vine – slender, woody stems. d. Tree – hard, strong stems that include a trunk, branches, & twigs. Wood – layers of xylem that build up year after year. Is made up of heartwood (dark) & sapwood (light). Bark – structure that helps prevent water loss in plants. Is made up of phloem, cork cambium, & cork.
Wood Composition
Roots 3. Roots – have 3 main functions : a. To absorb water & minerals. b. To anchor the plant. c. To store food (carrots).
There are 2 main types of roots : a. Taproot – a single large central root with much smaller side roots branching out from it. Grow deep to “tap” groundwater. b. Fibrous root – a clump of short, threadlike divisions. Found in the upper part of the soil. -Roots have tiny narrow tubes called root hairs to increase the surface area that is available for the absorption of water.
B. Plant Tissues 1. Dermal tissue – protective or surface tissue that forms the outermost tissue layer on leaves and stems. -On leaves dermal tissue is waxy to make them waterproof – cuticle. -On stems dermal tissue is thick bark, spongy cork, or tight sheath. -Some cells of dermal tissue contain chloroplasts, for photosynthesis. Main function of dermal tissue : to reduce water loss.
Vascular Tissue 2. Vascular tissue – tissue that transports or conducts materials around the plant. 2 Types of vascular tissue Xylem – vascular tissue that transports water & minerals up the plant. Phloem – vascular tissue that transports food (sugars from photosynthesis) down the plant. Main function of vascular tissue : transport materials.
Ground Tissue 3. Ground tissue – the fundamental tissue in plants (all remaining plant cells). Main function of ground tissue : support, especially in young & herbaceous plants.