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Transcript
Holt Cells, Heredity and Classification Chapter 1: The Basic Units of Life Section 1: Diversity of Cells • Cell – the smallest unit that can perform all the processes necessary for life - cells are covered by a membrane and have DNA and cytoplasm Section 1: Diversity of Cells • Cells - the basic units of structure and function in living things. Carry out all of organism’s processes, such as: obtaining oxygen, getting rid of waste, obtaining food, growing Form the parts of an organism First Observations of Cells • Microscope - an instrument that makes small objects look larger. • Made it possible to discover / learn about cells First Observations of Cells Simple Microscope • One lens Compound Microscope • More than one lens Robert Hooke • English scientist / inventor • One of the first people to observe cells • 1665 - used his microscope to observe a piece of cork • Called the empty spaces cells - “little rooms” • Thought animals weren’t made of cells since their cells didn’t have walls Anton van Leeuwenhoek • Dutch businessman • 1673 built his own microscopes • Observed fast-moving one-celled organisms in pond scum/water… called these animalcules • Also observed blood, bacteria and yeast cells Anton van Leeuwenhoek • Leeuwenhoek is a long, unusual word like animalcules Development of The Cell Theory • Almost 200 years passed before scientists concluded that cells are present in all living things • 1838 – Matthias Schleiden concludes that all plants are made of cells Development of The Cell Theory • 1839 – Theodor Schwann concluded that all animal tissues were made up of cells • Schwann wrote first 2 parts of Cell Theory 1) All organisms are made of one or more cells 2) The cell is the basic unit of all living things. Development of The Cell Theory • 1858 – Rudolf Virchow, a doctor, stated that all new cells could form only from other cells that already exist • This then added the third part of the Cell Theory 3) All cells come from existing cells The Cell Theory • The cell theory states that: 1) All organisms are made of one or more cells 2) The Cell is the basic unit of all living things. 3) All cells come from existing cells. Cell Size • Most cells are too small to be seen without a microscope • No one knew cells existed until they could see them with a microscope Skin cells Cell Size • As a cell’s volume increases, it’s surface area grows too. surface area surface area-to-volume ratio = volume Parts of a Cell • Cell membrane = a protective layer that covers the cell’s surface and acts as a barrier between inside of a cell and the cell’s environment (outside) Parts of a Cell • Cell membrane - controls what substances enter or leave the cell. 1 = cell wall 2 = cell membrane Parts of a Cell • cell membrane - controls what substances enter or leave the cell. - all cells have them - acts like a window screen Parts of a Cell • cytoplasm = fluid inside a cell Parts of a Cell • organelles - structures that perform specific function within the cell. organs - structures that carry out functions in a body organelles - structures that carry out functions in a cell Different types of cells have different organelles Parts of a Cell • Nucleus – in a eukaryotic cell; a membrane bound organelle that contains the cell’s DNA and has a role in processes such as growth, metabolism and reproduction • the cell’s control center • Acts as the brain of the cell Two Kinds of Cells • prokaryote = an organism that consists of a single cell that does not have a nucleus • Eubacteria and Archaebacteria Two Kinds of Cells • eukaryote = an organism made up of cells that have a nucleus enclosed by a membrane • animals, plants and fungi Section 2: Eukaryotic Cells Cell Wall • cell wall - a rigid structure that surrounds the cell membrane and provides support to the cell Onion cells • Plants and algae have cell walls made of cellulose • Fungi –yeast and mushrooms Eukaryotic Cells • cell wall - a rigid layer of nonliving material that surrounds the cells of plants and some other organisms. – Helps to protect and support the cell – Made mostly of cellulose (a strong material) – Allows some materials (such as water and oxygen) to pass through Cell Membrane • All cells have a cell membrane • Protective barrier that encloses a cell • Separates contents from environment • a gel-like fluid • Contains proteins, lipids, and phospholipids • Lipids – include fats and cholesterol, are a group of compounds that do not dissolve in water • Phospholipids – a lipid that contains phosphorous Cytoskeleton • a web of proteins in the cytoplasm • acts as both a muscle and a skeleton • keeps the cell’s membranes from collapsing • helps some cells move • made of 3 types of proteins Nucleus • all eukaryotic cells have a nucleus • a large organelle • contains the cell’s DNA = genetic material Nucleus • Nucleus has a dark area of many cells called the nucleolus which is where a cell begins to make its ribosomes Ribosomes • ribosomes – cell organelle composed of RNA and protein; the site of protein synthesis (small, grainlike bodies that produce proteins) Ribosomes • ribosomes - small, grainlike bodies that produce proteins. important chemicals needed to carry out bodily functions. Protein Jobs Endoplasmic Reticulum • endoplasmic reticulum – a system of folded membranes that in which proteins, lipids and other materials are made Endoplasmic Reticulum • The internal delivery system of the cell • Its folded membranes contain many tubes and passageways • Substances move through the ER to different places in the cell Rough ER • Covered in ribosomes • Usually found near nucleus • Ribosomes on rough ER make many of cell’s proteins • ER delivers these throughout the cell Smooth ER • Not covered in ribosomes • Functions include making lipids and breaking down toxic materials that could damage cell Mitochondria • mitochondria – main source of power in a cell - where sugar is broken down to produce energy Mitochondria • energy released by mitochondria is stored in a substance called ATP which a cell used to do work Chloroplasts • chloroplasts – where photosynthesis takes place sunlight + CO2 + H2O =(makes) sugar + O2 Chloroplasts • only found in plant and algae • contain chlorophyll = makes plants green Golgi Complex • Golgi complex - receives proteins and other newly formed materials from the endoplasmic reticulum, packages them, and distributes them to other parts of the cell, or outside the cell. Golgi Complex • Lipids and proteins from ER may be modified to do different jobs • Final products are enclosed in a piece of golgi complex’s membrane that is pinched off – forms a bubble and is transported to other parts of cell or out of cell Vesicle • The bubble that forms from the golgi complex’s membrane is a vesicle • A small sac that surrounds material to be moved in or out of cell Lysosomes • lysosomes – vesicles responsible for digestion inside a cell • contain digestive enzymes • destroy worn out or damaged organelles, get rid of waste materials and protect cell from foreign invaders • mainly in animal cells Organelles in the Cytoplasm • vacuoles – large vesicle • In plants & fungi may act like lysosomes • Store digestive enzymes and aid in digestion within cell • Other vacuoles in plant cell store water and other liquids to help support cell (or will wilt) Section 3 The Organization of Living Things Benefits of Being Multicellular Larger size: even if small still larger than single celled organisms Longer life: life span not limited to that of a single cell Specialization: each type of cell has a particular job making the organism more efficient Cells Working Together • A tissue is a group of cells that work together to perform a specific job. Tissues • Animals have 4 basic types of tissues: • Nerve tissue • Muscle tissue • Connective tissue • Protective tissue TIssues • Plants have three types of tissues: • Transport tissues • Protective tissues • Ground tissues – where photosynthesis takes place Tissues Working Together • A structure that is made up of two or more tissues working together to perform a specific function is called an organ Plants also have organs – example a leaf is a plant organ Organs working together • A group of organs working together to perform a particular function is called an organ system. Organisms • Anything that perform life processes by itself is an organism. • An organism can be single celled or multicellular. Organization of Cells cell tissue organ organ system Structure and Function • In organisms, structure and function are related. • Structure is the arrangement of parts in an organism. • Function is the job the part does.