Question

1. NE Extracellular materials in animal and plant cells a) What is the name on the extracellular layer located outside the plasma membrane of an animal cell? What type of macromolecule is this layer made of? b) What is the name of the extracellular layer located immediately outside the plasma membrane of a plant cell? What type of macromolecule is this extracellular layer made of? 2. Leaf structure a) Briefly explain why having small, needle-like leaves is adaptive in environments in which rainfall is limited. b) A disadvantage of small, needle-like leaves is a decrease in the efficiency of photosynthesis. Briefly explain why.

Answer 1

1)a) In case of animal there are no extracellular layer outside the plasma membrane.

b) In case of plants there is cell wall outside the plasma cell.

In plants, the cell wall is composed mainly of strong fibers of the carbohydrate polymer cellulose. Cellulose is the major component of cotton fiber and wood, and it is used in paper production.

2)a)The spines of cacti are actually modified leaves. It helps to imagine cacti as large stems with spines for leaves. One of the main functions of spines is fairly obvious – they protect cacti from predators.

But their needles still offer some nifty advantages over leaves—especially in tough climates or soil conditions: Needles have a thick, waxy coating that retains more water than a regular leaf. Since needles don't shed each fall they can capture sunlight for nearly the entire year.

b)small needle like leaves have small surface area by which they can not afford photosynthesis.