Cell Structure and Function HONORS BIOLOGY CH 3

Section 7-1 Life is Cellular Objectives Objectives Explain what the cell theory is Explain what the cell theory is Describe how researchers explore the living cell Describe how researchers explore the living cell Distinguish between eukaryotes and prokaryotes Distinguish between eukaryotes and prokaryotes

The Discovery of the Cell Early Microscopes –Robert Hooke used an early compound microscope to look at a thin slice of cork, a plant material. –Hooke observed what looked like empty chambers and called them “cells”.

The Cell Theory All living things are composed of cells All living things are composed of cells Cells are the basic units of structure and function in living things. Cells are the basic units of structure and function in living things. New cells are produced from existing cells. New cells are produced from existing cells.

Exploring the Cell Electron microscopes are capable of revealing details as much as 1000 times smaller than those visible in light microscopes. Electron microscopes are capable of revealing details as much as 1000 times smaller than those visible in light microscopes.

Prokaryotes and Eukaryotes

All cells have two characteristics in common: –They are surrounded by a barrier called a cell membrane. –They contain a molecule that carries DNA. Cells fall into two broad categories: Eukaryotes_ are cells that contain nuclei. –Prokaryotes are cells that do not contain nuclei.

–Prokaryotes  Generally smaller and simpler cells.  Contain genetic material that is not contained in a nucleus. Example: bacteria Example: bacteria

Eukaryotes –Generally larger and more complex cells.  Contain a nucleus in which their genetic material is separated from the rest.  Examples: plants, animals, fungi, and protists

Section 7-2 Eukaryotic Cell Structure Objectives Describe the function of the cell nucleus Describe the functions of the major cell organelles Identify the main roles of the cytoskeleton.

Comparing the Cell to a Factory –Organelles are known literally as “little organs”. –The eukaryotic cell is divided into two major parts: the nucleus and the cytoplasm.

Nucleus – the control center of the cell Nucleus – the control center of the cell –Contains nearly all the cell’s DNA and with it the coded instructions for making proteins and other important molecules. –Surrounded by a nuclear envelope composed of two membranes.

–The granular material you can see in the nucleus is the chromatin.  Consists of DNA bound to a protein.  When a cell divides, chromatin condenses to form chromosomes. –The nucleus also contains a small, dense region known as the nucleolus, where the assembly of ribosomes begins.

Ribosomes Ribosomes –Proteins are assembled on ribosomes. –Ribosomes are small particles of RNA and protein found in the cytoplasm.

Endoplasmic Reticulum –The endoplasmic reticulum is where lipid components of the cell membrane are assembled, along with proteins and other materials that are exported from the cell. –Rough ER synthesizes proteins. –Smooth ER contains enzymes that perform tasks such as the detoxification of drugs.

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

Lysosomes –Lysosomes are small organelles filled with enzymes  Involved in breaking down organelles that are no longer useful.

Vacuoles –Vacuoles are saclike structures that store materials such as water, salts, proteins, and carbohydrates. –In plant cells, there is a single, large central vacuole filled with liquid.

Mitochondria  Nearly all eukaryotic cells contain mitochondria.  Mitochondria are organelles that convert the chemical energy stored in food into compounds that are more convenient for the cell to use.

–Chloroplasts  Organelles that capture energy from sunlight and convert it into chemical energy in a process called photosynthesis.

–Organelle DNA  Chloroplasts and Mitochondria contain their own genetic information in the form of small DNA molecules

Cytoskeleton Eukaryotic cells have a cytoskeleton that helps support the cell. Eukaryotic cells have a cytoskeleton that helps support the cell.  A network of protein filaments that helps the cell to maintain its shape. Helps cells move Helps cells move

Section 7-3 Cell Boundaries Objectives Objectives Identify the main functions of the cell membrane and the cell wall Identify the main functions of the cell membrane and the cell wall Describe what happens during diffusion Describe what happens during diffusion Explain the processes of osmosis, facilitated diffusion, and active transport Explain the processes of osmosis, facilitated diffusion, and active transport.

Cell Membrane All cells are surrounded by a thin, flexible barrier known as the cell membrane. All cells are surrounded by a thin, flexible barrier known as the cell membrane. –Regulates what enters and leaves the cell and also provides _protection and _support_.

Cell Walls –The main function is to provide support_ and _protection___.  Cell walls lie outside the cell membrane.  Cell walls are present in plant, algae, fungi, and many prokaryotes.

Diffusion Through Cell Boundaries Measuring Concentration - The concentration of a solution is the mass of solute in a given volume of solution, or mass/volume.

Diffusion –Particles move from an area where they are more_ concentrated to an area where they are less_ concentrated, a process know as diffusion_. –When the concentration of the solute is the same throughout the system, the system has reached equilibrium. –Substances diffuse across membranes without requiring the cell to use energy.

Diffusion /eb/Diffusion.gif /eb/Diffusion.gif /eb/Diffusion.gif

Osmosis –If a substance is able to diffuse across a membrane, the membrane is said to be permeable to it. –Osmosis is the diffusion of water through a selectively permeable membrane.

Osmosis

How Osmosis Works When two solutions are the same on both sides of the membrane they are said to be isotonic. When two solutions are the same on both sides of the membrane they are said to be isotonic. The more concentrated solution is hypertonic_. The more concentrated solution is hypertonic_. The diluted solution is hypotonic The diluted solution is hypotonic

Osmotic Pressure Osmosis exerts a pressure known as osmotic pressure on the hypertonic side of a selectively permeable membrane. Osmosis exerts a pressure known as osmotic pressure on the hypertonic side of a selectively permeable membrane. Can cause problems for the cell, such as bursting. Can cause problems for the cell, such as bursting.

Facilitated Diffusion Cell membranes have protein channels that help molecules, such as glucose, to cross the membrane. Cell membranes have protein channels that help molecules, such as glucose, to cross the membrane.

Active Transport Active transport requires energy to transport materials against a concentration difference. Active transport requires energy to transport materials against a concentration difference. Molecular Transport Molecular Transport –Small molecules and ions are carried across membranes by proteins in the membrane that act like energy- requiring pumps

Endocytosis and Exocytosis

Endocytosis is the process of taking material into the cell by means of infoldings, or pockets, of the cell membrane. Endocytosis is the process of taking material into the cell by means of infoldings, or pockets, of the cell membrane. –The pocket that results breaks loose to form a vacuole_.

Phagocytosis means “cell eating”. Phagocytosis means “cell eating”. –Extensions of cytoplasm surround a particle and package it within a food vacuole. –The cell then engulfs it.

Pinocytosis is a process in which pockets along the cell membrane fill with liquid, and pinch off to form vacuoles within the cell. Pinocytosis is a process in which pockets along the cell membrane fill with liquid, and pinch off to form vacuoles within the cell. Many cells also release large amounts of material from the cell, a process known as exocytosis. Many cells also release large amounts of material from the cell, a process known as exocytosis.

Section 7-4 The Diversity of Cellular Life Objectives Objectives Describe cell specialization Describe cell specialization Identify the organization levels in multicellular organisms Identify the organization levels in multicellular organisms.

Unicellular Organisms Unicellular Organisms –A single-celled organism is also called a unicellular organism. –Unicellular organisms dominate life on Earth.

Multicellular Organisms Specialized Animal Cells Specialized Animal Cells –A process in which cells throughout an organism can develop in different ways to perform different tasks is called cell specialization. –Examples: red blood cells, pancreatic cells, and muscle cells.

Specialized Plant Cells Specialized Plant Cells –Specialized cells, known as guard cells, regulate the exchange of carbon dioxide, oxygen, water vapor, and other gases through tiny openings called stomata

Levels of Organization The levels of organization in a multicellular organism are individual cells, tissues, organs, and organ systems. The levels of organization in a multicellular organism are individual cells, tissues, organs, and organ systems.

Tissues Tissues –Cells are grouped into units called tissues. –Tissue is a group of similar cells that perform a particular function. –Animals have four common types: muscle, epithelial, nervous, and connective tissue.

Organs Organs –Many groups of tissues work together as an organ. Organ Systems Organ Systems –A group of organs that work together to perform a specific function is called an organ system.