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Transcript
Chapter 4 Section 2 Cell Structure and Function Review Who am I? What did I do? Robert Hooke 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.” Review: Who am I? Anton van Leeuwenhoek was a Dutch lens maker, who was the first person to observe living cells. 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.” Review: Cell Theory • Key players in the Cell Theory: – Matthias Schleiden – Theodor Schwann – Rudolph Virchow 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 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. 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? Main Cell Parts • What are the 3 main cell structures that control most of the activities in the cell? – Cell membrane – Nucleus – Cytoplasm 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. 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. 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. 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. 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. 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. 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. 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.