Chapter 4 Section 2 Cell Structure and Function

1. Chapter 4Section 2 Cell Structure and Function

2. ReviewWho am I? What did I do? Robert Hooke

3. Robert Hooke • He was an English scientist who cut a thin slice of cork and looked at it with a homemade microscope in 1665. • Hooke compared what he observed to the cells, or box-like rooms, in which monks slept. • Therefore he named the structures that make up cork “cells.”

4. Review: Who am I? Anton van Leeuwenhoek was a Dutch lens maker, who was the first person to observe living cells.

5. Anton van Leeuwenhoek • used a simple microscope he had made to observe such things as blood, rainwater, and teeth scrapings. • In 1675, he observed single-celled organisms in a drop of pond water, which he called these tiny living things “animalcules.”

6. Review: Cell Theory • Key players in the Cell Theory: • Matthias Schleiden • Theodor Schwann • Rudolph Virchow

7. Cell structure and Function • In the cell theory, cells are described as the basic unit of structure and function in living things. • Do you know why the cell is described this way? • Example: brick house

8. Cell structure and Function (cont.) • Many different kind of cells make up your body. • In fact, every cell in your body is adapted to its function. • Most cells are very small. • Plant and animal cells usually are between 10 and 50 micrometers in size. • The smallest cell may be 0.2 micrometers in diameter.

9. Cell structure and Function (cont.) • Some cells may be very large. • Several nerve-cell axons in your legs are about 1 meter long. • A large cell that is found in many animals is an egg. • Ex: a single cell that you probably see everyday is a chicken egg. • How many cells do you think make up and ostrich egg?

10. Main Cell Parts • What are the 3 main cell structures that control most of the activities in the cell? • Cell membrane • Nucleus • Cytoplasm

11. Cell Membrane • Cells are enclosed by a thin structure called the cell membrane. • It is a living part of the cell made mostly of lipids and proteins. • It is sometimes called the plasma membrane.

12. Cell Membrane (cont.) • The cell membrane has 3 important jobs: • Protect the inside of the cell by separating the cell from its surroundings. • Support the cell and give it shape. • Controls the passage of substances into and out of the cell.

13. Cell Wall • Some cells, such as plant cells, have a structure surrounding the cell membrane called the cell wall. • Unlike the cell membrane, the cell wall is not a living part of the cell. • Cell wall is made mostly of cellulose. • It is a carbohydrate made up of many sugar molecules linked together. • The cell wall also contains pectin, which is a starch used to thicken jams and jellies.

14. Cell Wall (cont.) • The cell wall has several functions: • It protects the cell and give it shape. • Provides cell with support. • Because of the support provided by the cell wall, large plants do not need a skeleton.

15. Nucleus • The nucleus is the “control center” of the cell. • It controls most of the activities that take place in the cell. • It controls cell reproduction. • What would happen to a cell if the nucleus were removed? • The cell would not be able to carry on its activities or reproduce. It would die.

16. Nucleus (cont.) • The nucleus is separated from the rest of the cell by the nuclear membrane. • Like the cell membrane, the nuclear membrane has 3 jobs. What do you think the 3 jobs are? • Protects the inside of the nucleus. • Support the nucleus and give it shape. • Controls the passage of substances into and out of the nucleus.

17. Nucleus (cont.) • Within the nucleus there are nucleoli, which makes rRNA. • These molecules are involved in making proteins. • Chromosomes are also located in the nucleus. • They control heredity. • Heredity is the passing of traits from parent to offspring.

18. Cytoplasm • Cytoplasm is all the living substance in a cell except the nucleus. • Most of the life processes take place within the cytoplasm of the cell.