CELLS

The Basic Unit: Cells  Cells – tiny living structures that make up all living things  A human liver – which weighs about 3 lb, is made up of over 300 billion cells!  Whole body estimate? 60 trillion  Not all cells are alike; some are specialized (they perform functions that no other cells do  Blood cells, muscle cells, nerve cells, gland cells

The Cell Theory  Robert Hooke (1665) – the first to use the word “cell” to describe what he saw  Observed a piece of cork through a microscope  What he actually saw were the walls of dead plant cells  Later scientists observed living things – they observed protoplasm  One made observation of plants. Another of animals

The Cell Theory  All of these observations were combines to form the modern cell theory:  All cells come from preexisting cells  All living things are made of cells and of the products of cells  The functions of living things are performed by the cells they are made of

Cellular Functions  All cells use energy  All cells manufacture materials  All cells respond to their environment  All cells reproduce themselves

Answer the following questions:  Who was the first English scientist to use the word “cell”?  According to the cell theory, can anything not made of cells be alive? Explain your answer.  What happens when a cell stops using energy?

Answer the following questions:  Who was the first English scientist to use the word “cell”?  According to the cell theory, can anything not made of cells be alive? Explain your answer.  What happens when a cell stops using energy?

Molecules and Life  The smallest unit that can be alive is the cell – but there are smaller structures within a cell  The smaller structures are essential for organism survival  Molecule – made up of atoms  Most molecules belong to 1 of 4 categories:  Carbohydrates  Proteins  Nucleic acids  Lipids (fats)

Molecules and Life  Molecules from these categories:  Are used to build cells  Store energy  Regulate cell activities  Store genetic information

Carbohydrates  Sugars and starches  They are made of only carbon, hydrogen, and oxygen atoms  Simple sugar: glucose (C 6 H 12 O 6 )  Other examples: cellulose, starch, glycogen

Proteins  They are very diverse and involved in almost everything a living cell does!  They may:  Store food  Fight disease (antibodies)  Help your muscles move  Enzymes  Made up of amino acids  There are 20 common amino acids (the arrangement is important, especially for enzymes)

Nucleic Acids  How does a cell know which amino acids to line up to build the proper protein? This information is stored in the cell’s DNA  Nucleic acids contain all the instructions that living cells need to make proteins and maintain life.  Made up of smaller molecules: nucleotides  Two major kinds of nucleic acids:  DNA  RNA

Nucleic Acids  Three things you need to know about nucleic acids:  The arrangement of the nucleotides in DNA forms a code  The DNA code determines which amino acids will be in a protein  The RNA helps in protein synthesis by using the coded instructions in DNA

Lipids  Fats and lipids are the same things  Too much can be unhealthy…but they are important to maintaining good health.  It serves as energy storage  Membranes contain lipids  Lipid molecules in a membrane:  Structural  Communicative  Transportive

Warm-up  What are cell membranes?  Get out a sheet of paper and tell me what you know about them. You may use your book!  (Chapter 4)

Membranes  Each cell is surrounded by a cell membrane, a thin covering that forms the outer boundary of the cell  Membranes sense and respond to changes in the surrounding environment  Membrane structure:  Composed of molecules of lipids and proteins  The most accurate model: Fluid mosaic model  Lipid molecules form a flexible (fluid), two-layered film in which proteins are embedded

Membrane Properties  Selective Permeability:  This means only certain molecules can go through the cell membrane  Molecules of water, oxygen, and carbon dioxide are small enough to pass, but others are too large (starch and protein)  One of the main ways that substances can pass through is by passive transport  Movement of substances across a membrane without using energy

Membrane Properties  Diffusion  A movement of molecules from an area of high concentration to low until it reaches equilibrium  Osmosis  The diffusion of water through a selectively permeable membrane  Active transport  Another way substances move across the membrane – but REQUIRES ENERGY!  Movement from area of low concentration to high OR when molecules are too big to pass

Leeuwenhoek  Let’s read the Facet together…  The Father of Microscopy  He called the organisms he viewed “animalcules” (or beasties)  COMPLETE SR P. 54 #1-5  COMPLETE IDEAS 4A & 4B

Answer the following ?’s  The thin covering that cells have is the ___________  Name the membrane model that is considered to be the most accurate.  What did Leeuwenhoek call the organisms he views with his microscopes?  Does osmosis require a cell to expend energy?  What type of transport requires energy?

Typical Parts of Cells  Cell are like tiny factories in many ways  Factories have: headquarters, power supplies, manufacturing equipment, clean-up crews, and shipping departments  All cells have three basic parts:  Cellular boundaries  The cytoplasm  Genetic material

Typical Parts of Cells  Cell boundaries  Plants – cell walls  Animal cell – cell (plasma) membrane  Keep things in and out; controls what allows to go in and out  Cytoplasm  A thick fluid that contains many organelles  Organelles – the parts of the cell that perform many functions needed to keep the cell alive  Genetic Material  Nucleus – compact, roundish structure that functions as the control center of the cell. This contains the genetic info (DNA)

Typical Parts of Cells  Organelles in the Cytoplasm:  Mitochondria – the cell’s powerhouse; site of energy production

Typical Parts of Cells  Organelles in the Cytoplasm:  Endoplasmic Reticulum – ER for short; a maze of passageways; it connects the nucleus to the cell membrane; functions as the cell’s delivery system.

Typical Parts of Cells  Organelles in the Cytoplasm:  Ribosomes – tiny organelles directing the assembling of proteins; serve as major building materials of cells; scattered throughout the cytoplasm or attached to the ER; These make PROTEINS!

Typical Parts of Cells  Organelles in the Cytoplasm:  Golgi Apparatus – chemicals from the cytoplasm are collected here; believed to be connected with the ER; packages chemicals and distributes them throughout the cell

Typical Parts of Cells  Organelles in the Cytoplasm:  Vacuoles – look like bubbles and serve as containers inside the cytoplasm of some cells; may contain food, water, wastes, fats, or chemicals being

Typical Parts of Cells  Organelles in the Cytoplasm:  Lysosomes – tiny-enzyme filled capsules; circulate in the cytoplasm and us their enzymes as a demolition crew; dissolve away cellular structures not needed; also help keep foreign invaders out.

Typical Parts of Cells  Organelles in the Cytoplasm:  Chloroplasts – ONLY IN PLANT CELLS; contain chlorophyll (which captures energy from sunlight and the energy is then used to make sugar through a process called photosynthesis)

Typical Parts of Cells  Organelles in the Cytoplasm:  Nucleus – compact, roundish structure; functions as the control center; contains genetic information of the cell; surrounded by a nuclear membrane; contains chromosomes (composed of DNA)

Typical Parts of Cells  Cilia and Flagella  Cilia – short, hair like structures on the outer part of a cell  Flagella – a single, whiplike tail  Both provide for movement

Cellular Organization  Most cells need other cells to survive  Exception: paramecium; unicellular; feeds itself  Larger organisms divide the functions they need to survive among many cells.  Tissue: a group of cells working together to perform a specific function  Organ: groups of different kinds of tissues that work together to accomplish a particular function  There is a division of labor among the tissues and organs or multicellular organisms

Cellular Respiration  Cellular respiration – the breakdown of an energy source (sugar) by cells to obtain useable energy.  This process requires many enzymes, which serve as catalysts  Catalysts – substances that help change other substances without being permanently changed themselves

Cellular Respiration  Sugar is the most common energy source in cellular respiration  It takes place in the cytoplasm and mitochondria  Sugar + oxygen  carbon dioxide, water, and energy.  Two types of cellular respiration:  Aerobic respiration – requires oxygen; make more useable energy  Anaerobic respiration – no oxygen

Cellular Respiration  Two types of anaerobic respiration (fermentation):  Alcoholic fermentation  Bread dough rising; leaven; yeast  Lactic acid fermentation  Yogurt, cottage cheese, buttermilk  Muscles – lactic acid build up can cause muscle soreness

Photosynthesis  The process that most producer organisms use to change light energy into chemical energy (producer organisms make their own food)  Carbon dioxide + water + light energy  sugar + oxygen  Light is changed to energy (sugar)  Occurs in the chloroplast, which contain chlorophyll  Chlorophyll, a green pigment, that absorbs light energy and uses it to power photosynthesis.

Photosynthesis  Chloroplasts:  Have two membranes  Contains things that look like stacks of coins