Ch. 7 – Cell Structure and Function Life is Cellular

Levels of Organization The levels of organization in a multicellular organism are individual cells, tissue, organs, and organ systems. Cells are an organisms basic unit Tissues are a group of cells working together. Example – muscle tissue Organs are a group of tissues working together. Example – the heart. Organ systems are a group of organs working together. Example – the digestive system.

The Discovery of the Cell Discovery of cells was possible with the invention of the microscope. In 1665 Robert Hooke was the first to use a microscope to look at cork cells. He called the boxes that he saw cells.

At the same time, Anton van Leeuwenhoek was the first to look at animals in pond water. He called these animals “animalcules”.

Soon, numerous observations made it clear that cells were the basic unit of life, and the cell theory was developed. The cell theory states: All living things are composed of cells. Cells are the basic units of structure and function in living things. New cells are produced from existing cells.

Exploring the Cell Electron microscopes Capable of revealing detail as much as 1000 times smaller than those visible with a light microscope. Two types: Transmission electron microscopes – cells and tissues must be sliced thin in order to be examined. Scanning electron microscopes – specimens do not have to cut into thin slices.

TEM SEM

TEM images SEM images

Scanning Probe Microscopes Power that is so precise, that a single atom can be observed.

Prokaryotes and Eukaryotes Prokaryotic cells – Do not have a nucleus. They are generally smaller than eukaryotes. Bacteria are an example of a prokaryote.

Eukaryotic cells- contain a nucleus in which their genetic material is separated from the rest of the cell. Some eukaryotes are unicellular like protists. Most eukaryotes are multicellular, plants, animals, fungi.

Topic: Eukaryotic Cell Structure Chapter 7 section 2 EQ: What are the functions of each cell organelle?

Comparing the Cell to a Factory In some ways, the eukaryotic cell is like a factory, it has many parts and functions.

Cell Organelles Organelle – means little organs, these are the main structures of the cell. Cytoplasm – is the portion of the cell that is outside the nucleus. It is what other organelles float in, and what is used to transport messages between other organelles.

Nucleus – this is the control center of the cell. The nucleus contains nearly all of the cell’s DNA and with it the coded instructions for making proteins and other important molecules. The nucleus is surrounded by a nuclear envelope. It is dotted with thousands of pores that allow material to move in and out.

The granular material in the nucleus is called chromatin. Chromatin consists of DNA bound to a protein, and will condense to form chromosomes. The nucleus also contains a nucleolus, which is where ribosomes are made.

Ribosomes Ribosomes – make and assemble proteins. They get their instructions from the nucleus, and are found either free floating in the cytoplasm or on top of the endoplasmic reticulum.

Endoplasmic reticulum – is the site where lipid components of the cell membrane are assembled, along with proteins and other materials that are exported from the cell. Endoplasmic reticulum with ribosomes on it is called rough ER. If it has no ribosomes it is called smooth ER. They are also involved in the detoxification of drugs in the body.

Golgi apparatus or golgi body – the function is to modify, sort, and package proteins and other material from the endoplasmic reticulum for storage in the cell or secretion outside the cell. The golgi apparatus is kind of like the UPS of the cell.

Lysosomes – are small organelles filled with enzymes. They break down lipids, carbohydrates, and proteins that can be used by the cells. They also break down dying organelles in the cell.

Vacuoles – store materials like water, salts, proteins, and carbohydrates. Plants have huge vacuoles to store water.

Mitochondria – are organelles that convert the chemical energy stored in food into compounds that are more convenient for the cell to use. In other words they make ATP, or energy. They have two membranes and their own DNA.

Chloroplasts – are only found in plants, and their job is to convert energy from sunlight into food during photosynthesis. They contain the pigment chlorophyll which makes a plant green.

Cytoskeleton – A network of protein filaments that helps the cell to maintain its shape. The cytoskeleton is also involved in movement. The cytoskeleton is made up of microfilaments and microtubules.

Cell Boundaries Chapter 7, section 3

Cell Membrane The cell membrane regulates what enters and leaves the cell and also provides protection and support The cell membrane is made up of a phospholipid bilayer. Meaning that the cell membrane has two layers.

Cell Walls Cell walls are present in plants, algae, and fungi. Cell walls lie outside of the cell membrane. The main function of the cell wall is to provide support and protection for the cell. Cell walls are made up cellulose, which is what your paper is made of.

Diffusion Through Cell Boundaries Diffusion – when materials pass from an area of high concentration to an area of low concentration, until the system has reached equilibrium. Because diffusion depends upon random particle movements, substances diffuse across membranes with-out requiring the cell to use energy.

Osmosis Osmosis – is the diffusion of water through a selectively permeable membrane, or semipermeable membranes. Selective permeability means that some but not all substances can pass through the cell membrane, some require energy to get through the membrane. Osmosis and diffusion do not require energy.

How osmosis works- Some solutions are isotonic meaning that they have equal parts. Some are hypertonic meaning they have more solute than solvent. Some are hypotonic meaning they have more solvent than solute. REMEMBER OSMOSIS IS WATER MOVING FROM AN AREA OF HIGH CONCENTRATION TO AN AREA OF LOW CONCENTRATION.

Facilitated Diffusion Facilitated diffusion – is the movement of specific molecules across cell membranes through protein channels. Like sugar. Requires no energy.

Active Transport Sometimes cells need to move substances from areas of low concentration to areas of high concentration. How cells do this is through active transport. This requires energy. Sometimes the transport of larger materials involves changes in the shape of the cell membrane.

Types of active transport – Endocytosis – is the process of taking material into the cell by means of infoldings, or pockets, of the cell membrane. Two types of endocytosis are: Phagocytosis – extensions of cytoplasm surround a particle and package it within a food vacuole. The cell then engulfs it. Pinocytosis – process by which a cell takes in liquid from the surrounding environment. Exocytosis – the forcing of material out of a cell.

The Diversity of Cellular Life

Unicellular Organisms A single celled organism is also called a unicellular organism In terms of numbers, Unicellular organisms dominate life on earth. Example - yeast

Multicellular Organisms Some organisms (like yourself) are made up of many cells. Cells throughout a multicellular organism can develop in different ways to perform different tasks. This is called cell specialization.

Animal and plant cells are specialized in many ways. They can transport oxygen, make proteins, store food, and digest food. They also help organisms to move Plant cells help it to make food, and get rid of oxygen.