CELL STRUCTURE AND FUNCTION CHAPTER 7 CELL STRUCTURE AND FUNCTION

SECTION 1 Life Is Cellular

Key Concept Questions: What is the cell theory? What are the characteristics of prokaryotes and eukaryotes?

Since the 1600s, scientists have made many discoveries that have showed how important cells are in living things. The cell theory grew out of the work of many scientists and improvements in the microscope. Many scientists contributed to the cell theory.

1600’s Anton van Leeuwenhoek was the first person to see tiny living organisms in a drop of water – he called them “animalcules”

1665 Robert Hooke looked at slices of cork and observed tiny chambers or “cells”

1838 Matthias Schleiden concluded plants are made of cells 1839 Theodor Schwann concluded animals are made of cells In 1858, Rudolph Virchow, a German physician, proposed that cells come only from the division of existing cells.

More was learned about cells as microscopes improved. The cell theory is a unifying concept of biology.

Early studies led to the development of the cell theory. The Cell theory has three principles. All organisms are made of cells.

All existing cells are produced by other living cells.

The cell is the most basic unit of life.

McDougall Littell video – Cell theory

All cells share certain characteristics. Bacterium (colored SEM; magnification 8800x) cell membrane cytoplasm All cells share certain characteristics. Cells tend to be microscopic. All cells are enclosed by a membrane. All cells are filled with cytoplasm.

There are two cell types: eukaryotic cells and prokaryotic cells. Prokaryotic cells do not have a nucleus. Prokaryotic cells do not have membrane-bound organelles. nucleus cell membrane organelles cytoplasm

The root kary means “kernel,” which describes the nucleus The root kary means “kernel,” which describes the nucleus. Eu- means “true,” so a eukaryotic cell has a true nucleus. If pro- means “before,” what does prokaryotic mean? Before a nucleus

Key Concept Questions: What is the cell theory? The cell theory states all living things are composed of cells, cells are the basic units of structure and function in living organisms, new cells come from existing cells. What are the characteristics of prokaryotes and eukaryotes? Both have a cell membrane and DNA. Prokaryotes do not have a nucleus but eukaryotes do.

Section 2 Eukaryotic Cell Structure

Key Concept Question What are the functions of the major cell structures?

Cell biologists divide the eukaryotic cell into two major parts: the nucleus and the cytoplasm. The cytoplasm is the portion of the cell outside the nucleus. Eukaryotic cells contain structures known as organelles. (The root word organ means a group of parts that work together. The suffix –elle means a small part.)

The cell membrane controls what enters and leaves the cell.

Cells have an internal structure. The cytoskeleton has many functions. supports and shapes cell helps position and transport organelles provides strength assists in cell division aids in cell movement

Several organelles are involved in making and processing proteins. The nucleus stores genetic information. Contains instructions for all proteins

Many processes occur in the endoplasmic reticulum.

There are two types of endoplasmic reticulum. rough endoplasmic reticulum smooth endoplasmic reticulum

Ribosomes link amino acids to form proteins.

Vesicles are membrane-bound sacs that hold materials.

The function of the Golgi apparatus is to modify, sort, and package proteins and other materials from the ER for storage in the cell or secretion outside the cell.

Other organelles have various functions. Mitochondria supply energy to the cell.

Vacuoles are fluid-filled sacs that store food, water, and waste

Lysosomes contain enzymes to digest material.

Centrioles are tubes found in the centrosomes. Centrioles help divide DNA. Centrioles form cilia and flagella.

Plant cells have cell walls and chloroplasts. A cell wall provides rigid support.

Chloroplasts convert solar energy to chemical energy.

McDougall Littell video Cell Structure 1

Smartboard Volunteer McDougall Littell Explore Cell Organelles – animated biology

Key Concept Question What are the functions of the major cell structures? Cell Membrane = controls what enters and leaves the cell Cell Wall = Provides support and protection to the cell Nucleus = control center Ribosomes = make proteins Smooth ER = makes lipids Rough ER = helps make proteins

Golgi = modify, sort, package proteins Vacuoles = store food, water, waste Lysosome = break down and digest materials Mitochondria = provides cell with energy Chloroplast = site of photosynthesis Cytoskeleton = structure, support and movement

Section 3 Cell Boundaries

Key Concept Questions: What are the main functions of the cell membrane and the cell wall?  What happens during diffusion?  What is osmosis?

Cell membranes are composed of two phospholipid layers. The cell membrane has two major functions. forms a boundary between inside and outside of the cell controls passage of materials cell membrane outside cell inside cell

The cell membrane is made of a phospholipid bilayer. There are other molecules embedded in the membrane. The fluid mosaic model describes the membrane. cell membrane protein cholesterol carbohydrate chain protein channel

The cell membrane is selectively permeable. Some molecules can cross the membrane while others cannot.

The cell membrane is selectively permeable. Some molecules can cross the membrane while others cannot.

Chemical signals are transmitted across the cell membrane. Receptors bind with ligands and change shape. There are two types of receptors. intracellular receptor

Chemical signals are transmitted across the cell membrane. Receptors bind with ligands and change shape. There are two types of receptors. intracellular receptor membrane

Materials move across membranes because of concentration differences Materials move across membranes because of concentration differences. When the concentration of a solute is the same throughout a solution, the solution has reached equilibrium.

Passive transport does not require energy input from a cell. Molecules can move across the cell membrane through passive transport. There are two types of passive transport. Diffusion Osmosis

Diffusion and osmosis are types of passive transport. Molecules diffuse down a concentration gradient. Diffusion is the movement of molecules from area of high cocentration to areas of low concentration Osmosis is the diffusion of water molecules across a semipermeable membrane.

Let’s practice with diffusion. How will the final picture look?

Let’s practice with osmosis. How will the final picture look? 70% water 30% water

50% water 50% water

There are three types of solutions. isotonic hypertonic hypotonic

freshwater balanced saltwater

Some molecules can only diffuse through transport proteins. Some molecules cannot easily diffuse across the cell membrane. Facilitated diffusion is diffusion through transport proteins.

Active Transport, Endocytosis, and Exocytosis Cells use energy to transport materials that cannot diffuse across a membrane.

Active transport requires energy input from a cell and enables a cell to move a substance against its concentration gradient. Passive transport requires no energy from the cell. Active transport is powered by chemical energy (ATP). Active transport occurs through transport protein pumps. Cells use active transport to maintain homeostasis.

A cell can import and export large materials or large amounts of material in vesicles during the processes of endocytosis and exocytosis. Cells use energy to transport material in vesicles. Endocytosis is the process of taking material into the cell. Phagocytosis is a type of endocytosis.

Exocytosis is the process of expelling material from the cell.

Some unicellular eukaryotes have contractile vacuoles, which collect excess water inside the cell and force the water out of the cell. http://www.linkpublishing.com/Videos/transport/para_osmotic.wmv

McDougall Littell animated biology - passive transport and plasma membrane

Smartboard Volunteer McDougall Littell animated biology – get through a cell membrane

Key Concept Questions: What are the main functions of the cell membrane and the cell wall?  The cell membrane controls what enters and leaves the cell. The cell wall provides structure and support. What happens during diffusion?  Molecules move from an area of high concentration to an area of low concentration What is osmosis? The diffusion of water molecules

Section 4 The Diversity of Cellular Life

Key Concept Questions: What is cell specialization?  What are the four levels of organization in multicellular organisms?

An organism that consists of a single cell is called a unicellular organism. Unicellular organisms carry out all the essential functions of life that larger organisms do. Organisms that are made up of many cells are called multicellular organisms. Cells throughout a multicellular organism can develop in different ways to perform different tasks. This process is called cell specialization or differentiation.

The levels of organization in a multicellular organism are individual cells, tissues, organs, and organ systems. Individual cells are the first level. Similar cells are grouped into units called tissues. A tissue is a group of cells that perform a particular function. Groups of tissues that work together form an organ. A group of organs that work together to perform a specific function is called an organ system.

Key Concept Questions: What is cell specialization?  Cells throughout a multicellular organism can develop in different ways to perform different tasks What are the four levels of organization in multicellular organisms? Cells, tissues, organs, and organ systems