CELL STRUCTURE AND FUNCTION LIFE IS CELLULAR

LIFE IS CELLULAR Prokaryotes and Eukaryotes Cells come in many sizes and shapes. Typical size 5 to 50 micrometers Tiniest mycoplasma bacteria is 0.2 micrometers across Giant amoeba Chaos chaos is 1000 micrometers (µm) in diameter. All cells have two things in common. They are surrounded by a barrier called a cell membrane. They contain the molecule that carries biological information-DNA.

MYCOPLASMA BACTERIA

CHAOS CHAOS AMOEBA

LIFE IS CELLULAR Cells are one of two categories, depending on whether they contain a nucleus or not. The nucleus (plural is nuclei) is a large membrane-enclosed structure that contains the cell’s genetic material in the form of DNA. The membrane is a thin layer of material that serves as a covering or lining. The nucleus controls many of the cells activities. Eukaryotes are cells that contain nuclei. Prokaryotes are cells that do not contain nuclei.

LIFE IS CELLULAR Prokaryotes These cells are usually smaller. They have genetic material that is not contained in a nucleus. Despite being simpler cells, they carry out every activity associated with living things. They grow They reproduce They respond to the environment They move by gliding along a surface or swim through liquids Bacteria are prokaryotes

PROKARYOTES

PROKARYOTES

LIFE IS CELLULAR Eukaryotes These cells are larger and more complex. They contain many structures and membranes, and are highly specialized. They contain a nucleus in which their genetic material is separated from the rest of the cell. Some are single celled and other are multicellular. Plants, animals, fungi are eukaryotes.

EUKARYOTES

EUKARYOTES

EUKARYOTES

EUKARYOTIC CELL STRUCTURE Comparing the Cell to a Factory The cellular structure of a eukaryotic cell seems, at first glance, to be very complex. However, after looking at the cell under a microscope, patterns begin to emerge. Organelles are within the eukaryotic cell and act like specialized organs, or organelles, “little organs.”

EUKARYOTIC PLANT CELL

EUKARYOTIC PLANT CELL

EUKARYOTIC PLANT CELL

EUKARYOTIC ANIMAL CELL

EUKARYOTIC ANIMAL CELL

EUKARYOTIC ANIMAL CELL

EUKARYOTIC CELL STRUCTURE The cell is divided into two parts The nucleus The cytoplasm The cytoplasm is the portion of the cell outside the nucleus. Nucleus The nucleus is the control center of the cell. The nucleus contains nearly all the cell’s DNA and with it the coded instructions for making proteins and other important molecules.

CELL NUCLEUS

CELL NUCLEUS

CELL NUCLEUS

EUKARYOTIC CELL STRUCTURE The nucleus is surrounded by the nuclear envelope. This is composed of 2 membranes. This has thousands of pores allowing material to move in and out of the nucleus. Allows RNA, proteins, and other molecules to move through the pores. The granular material in the nucleus is the chromatin. This consists of DNA bound to protein. When cells divide, the chromatin condenses to form chromosomes. Contain the genetic information passed from one cell to next.

EUKARYOTIC CELL STRUCTURE The nucleolus is in the nucleus and is where the assembly of ribosomes takes place. Ribosomes Proteins are assembled on ribosomes. Ribosomes are small particles of RNA and protein found in the cytoplasm. This turns out proteins on instructions that come from the nucleus.

EUKARYOTIC CELL STRUCTURE Endoplasmic Reticulum This is an internal membrane system where lipid components of the cell membrane is assembled, along with proteins and other materials that are exported from the cell. The rough ER is where proteins are produced. Ribosomes are found on its surface. No ribosomes are found on the smooth endoplasmic reticulum.

ENDOPLASMIC RETICULUM

ENDOPLASMIC RETICULUM

ENDOPLASMIC RETICULUM

EUKARYOTIC CELL STRUCTURE This contains enzymes that synthesize membrane lipids and detoxify drugs. Liver cells contain a lot of smooth ER since this is where most of the drugs are detoxified. Golgi Apparatus Proteins produced in the rough ER move into an organelle called the Golgi apparatus. The function of the Golgi apparatus is to modify, sort, and package proteins and other materials from the endoplasmic reticulum for storage in the cell or secretion outside the cell.

GOLGI APPARATUS

GOLGI APPARATUS

EUKARYOTIC CELL STRUCTURE The Golgi apparatus is where the finishing touches are put on the proteins before they leave the production area. Lysosomes These are the cleanup crew. These are small organelles filled with enzymes that digest, breakdown, lipids, carbohydrates, and proteins into small molecules that can be used by the rest of the cell.

EUKARYOTIC CELL STRUCTURE Lysosomes also breakdown organelles that have outlived their usefulness. They remove “junk.” Tay-Sachs disease can be traced to the failure of the lysosomes. Vacuoles This is the storage area. These are sac-like structures that store water, salts, proteins, and carbohydrates.

LYSOSOMES

VACUOLES

VACUOLES

EUKARYOTIC CELL STRUCTURE These also can pump water in and out of the cell to maintain homeostasis which controls the internal environment. Mitochondria and Chloroplasts Mitochondria Mitochondria are organelles that convert the chemical energy stored in food into compounds that are more convenient for the cell to use. These have an inner and outer membrane. These are inherited, in humans, from the ovum or egg.

EUKARYOTIC CELL STRUCTURE Chloroplasts Chloroplasts are organelles that capture the energy from sunlight and convert it into chemical energy in a process called photosynthesis. Chlorophyll is contained here. Organelle DNA Chloroplasts and mitochondria contain their own genetic information in the form of small DNA molecules.

MITOCHONDRIA

MITOCHONDRIA

MITOCHONDRIA

CHLOROPLASTS

CHOROPLASTS

EUKARYOTIC CELL STRUCTURE Cytoskeleton The supporting structure of the cell is the cytoskeleton. The cytoskeleton is a network of protein filaments that helps the cell to maintain its shape. The cytoskeleton is also involved in movement. Made up of protein filaments Microfilaments Microtubules

EUKARYOTIC CELL STRUCTURE Microfilaments support the cell and allow cells such as amoebas to move. Microtubules help to maintain cell shape Also help in cell division with structures known as centrioles. Help to build cilia and flagella that enable the cell to swim rapidly in liquids.

CYTOSKELETON

CYTOSKELETON

CELL BOUNDARIES Diffusion In solutions, particles move constantly. Particles collide with one another and spread out randomly. Particles move from areas where they are more concentrated to areas where they are less concentrated, also known as diffusion. They do this until the concentration of particles is the same throughout the system, known as equilibrium.

CELL BOUNDARIES Because diffusion depends upon random particle movements, substances diffuse across membranes without requiring the cell to use energy. After equilibrium is reached, there is still movement of particles across the cell membrane but the movement is equal in both directions.

DIFFUSION

DIFFUSION

DIFFUSION

CELL BOUNDARIES Osmosis Some substances might be too large or too charged to cross the cell membrane (lipid bilayer). Membranes that are permeable indicates that substances can diffuse across it. Impermeable membranes are those that substances cannot diffuse across. Most biological membranes are selectively permeable.

CELL BOUNDARIES Water passes through quite easily while some solutions cannot. Osmosis is the diffusion of water through a selectively permeable membrane. How Osmosis Works Take the example of a beaker with a permeable membrane in the middle. On one side is a low concentration of sugar water, on the other is a high concentration of sugar water. Water will move from the higher concentration (water) to the lower concentration (water + sugar) across the membrane.

CELL BOUNDARIES The membrane is permeable to water but not to sugar. This movement of water will occur until there is an equilibrium, or an equal amount on both sides of the membrane of water and sugar. When this happens, the two solutions are said to be isotonic (same strength). The more concentrated solution is hypertonic (above strength) and the less concentrated solution is hypotonic (below strength).

OSMOSIS

LEVELS OF CELL ORGANIZATION

LEVELS OF CELL ORGANIZATION The levels of organization in a multicellular organism are individual cells, tissues, organs, and organ system. Tissues In multicellular organisms, cells are the first level of organization. Similar cells are grouped into units called tissues. A tissue is a group of similar cells that perform a particular function.

LEVELS OF CELL ORGANIZATION

LEVELS OF CELL ORGANIZATION

LEVELS OF CELL ORGANIZATION

LEVELS OF CELL ORGANIZATION Most animals have four main types of tissue Muscle Epithelial Nervous Connective tissue Organs Many types of tissues work together as an organ. The tasks of the body are too complex for just one type of tissue to perform the task. Each type of tissue performs an essential task to help the organ function.

LEVELS OF CELL ORGANIZATION Organ Systems A group of organs that work together to perform a specific function is called an organ system. Specialized cells such as nerve and muscle cells are able to function precisely because other cells are specialized to obtain the food and oxygen needed by those cells. This overall specialization and interdependence is one of the remarkable attributes of living things.