2Cells Life has a cellular basis. All organisms, including humans, are composed of cells.There is no smaller unit of life that is able to: reproduce, respond, grow & develop, and take in and use materials from the environment.The work of 17th century scientists who had invented early microscopes and those that used them led to one of the fundamental principles of modern biology, the Cell Theory.
4The Cell Theory States: Cells are the basic working unit of life.2. All living things are made up of one or more cells.3. New cells arise only from pre-existing cells.
5Cell SizeThe ratio of surface-area-to-volume explains the small size of cells.Nutrients enter a cell and wastes exit a cell at its surface.The ability to get more materials in and out depends on a greater amount of surface area.Volume represents cell needs.
6Cell SizeProportionally as a cell grows it becomes larger in volume and surface area decreases.There is a limit to how large an actively metabolizing cell can become.Cell division restores the amount of surface area needed for adequate exchange of materials.
8Microscopes Microscope use and its parts will be studied in lab. Light microscopesUse glass lenses & light rays to obtain imagesBetter suited for living specimensLower magnificationElectron microscopesUse electrons to obtain imagesObtain higher magnification and resolutionMicroscope use and its parts will be studied in lab.
9How Cells are Organized Cells can be classified as either prokaryotic or eukaryotic.Prokaryotic cells contain no membrane-bound organelles and lack a nucleus.They have a plasma membrane and contain cytoplasm; have ribosomes, and a ring of DNA.Most prokaryotes are bacteria.
10How Cells are Organized You and nearly all other life forms that you experience with your unaided eyes are eukaryotes.The vast majority of eukaryotes that we knowingly interact with each day, mainly land plants and animals are large organisms, usually consisting of trillions of cells.
11How Cells are Organized Almost all eukaryotic cells have 3 main areasAn outer membrane called the plasma membrane.A semifluid medium inside called the cytoplasm.The substance contains various organelles (small specialized structures).3. A large central membrane-enclosed nucleus, where DNA is found.
12Cellular Organization Nucleus Central sphere of the cellPlasma Membrane Outer boundary between the cell and the environmentCytoplasm Everything between the plasma membrane and the nucleusOrganelles Specialized structures in the cytoplasm
14Plasma Membrane - Structure The plasma membrane is the boundary between the outside and inside of the cell.The plasma membrane is a phospholipid bilayer with attached or embedded proteins.At body temperature the bilayer is a liquid.This allows the proteins to move about.This structure of being liquid and having shifting proteins is described as the fluid-mosaic model.
15Plasma Membrane - Structure Short chains of sugars attach to the proteins and lipids and are called glycoproteins and glycolipids. They mark cells as belonging to a particular individual.A common example of this can be seen in the different blood types of people.
17Plasma Membrane - Functions The plasma membrane keeps the cell intact.The plasma membrane allows only certain molecules to enter and exit freely.Therefore, the plasma membrane is said to be selectively permeable.
18Passive TransportPassive transport is a way for molecules to enter or exit a cell without using cellular energy.Diffusion is the random movement of molecules from an area of higher concentration to an area of lower concentration until they are equally distributed.
19Osmosis Osmosis is the diffusion of water across a semi-permeable membrane.
20TonicityTonicity is the term used to describe the solute concentration in a solution surrounding a cell.Example: 2% salt solution (98% water)
21Solution Types - Identified by Tonicity Isotonic – Solution outside of the cell is equal in concentration of water and solute.This causes cells to: Neither gain nor lose water. Normal cell size and shape maintained.Hypotonic – Solution outside of the cell with a higher concentration of water and lower solute.This causes cells to: Gain water.Cells increase in size or burst.
22Solution Types - Identified by Tonicity Hypertonic – Solution outside of the cell has a lower concentration of water and higher solute.This causes cells to: Lose water.Cells shrink or shrivel in size.Osmotic pressure controls water movement in our bodies.Examples: Absorption in the small and large intestine and in the kidneys.
24Facilitated Transport The transport of solutes from high to low concentration by means of protein carriers within the membrane.This transport is also without using cell energy.
25Active TransportOccurs when a molecule is moving from a lower to higher concentration.Movement requires a protein carrier and the use of cellular energy.Protein carriers act like a pump to move molecules against their concentration gradient (low to high).
26EndocytosisEndocytosis occurs when a portion of the plasma membrane forms a pouch to surround a substance and fluid. The membrane pinches off and forms a vesicle.
27Types of EndocytosisWhen cells like white blood cells do endocytosis and the membrane pushes out to engulf a particle like a bacterium, the process is called Phagocytosis.Pinocytosis is taking in small molecules and fluid. The membrane invaginates forming a vesicle.
31The nucleus and several organelles are involved in the production and processing of proteins. The nucleus is the largest structure in the cell, usually spherical, found near the center and stores genetic information.Segments of DNA threads called genes contain information for the production of specific proteins.The nucleus is thus called the control center of the cell.
32Threads found inside are made of DNA and protein and are called chromatin. These threads are immersed in a semifluid medium called nucleoplasm.The nucleolus is a dark dense region where ribosomal RNA is produced and joins with protein to form subunits called ribosomes.
33The nuclear envelope separates the nucleus from the cytoplasm and is perforated with passageways called nuclear pores.Nuclear poresNucleoplasmNucleousNuclear EnvelopeEndoplasmicreticulum
34Ribosomes Ribosomes are tiny granules composed proteins and rRNA. Ribosomes are where protein synthesis occurs.Ribosomes are often attached to membranes in the cytoplasm called the endoplasmic reticulum (ER).Ribosomes can also be found alone in the cytoplasm or in groups called polyribosomes.
35The Endomembrane System The endomembrane system consists of the:Nuclear envelopeEndoplasmic reticulumGolgi apparatusLysosomesVesicles
37The Endoplasmic Reticulum The endoplasmic reticulum (ER) is a system of membranes within the cytoplasm and continuous with the nuclear envelope.Two types are:Rough ER is studded with ribosomes on the cytoplasm side.Proteins are synthesized here.
38The Endoplasmic Reticulum Smooth ER lacks ribosomes and is the site of synthesis of phospholipids and other substances.The ER forms vesicles, which are membrane sacs used to transport substances.
40The Golgi ApparatusThe Golgi apparatus consists of a stack of curved saccules.The Golgi apparatus receives protein and lipid-filled vesicles from the ER.Ends of the saccules expand forming vesicles, which leave the Golgi apparatus.The Golgi apparatus processes, packages, secretes, and distributes substances within and out of the cell.
42Lysosomes Lysosomes are vesicles produced by the Golgi apparatus. Lysosomes contain hydrolytic enzymes.All body cells have lysosomes, but certain white blood cells have many and use them to help protect us from disease-causing microbes.
43Lysosomes Lysosomes can fuse with vesicles to digest their contents. They engulf, digest, and release simpler substances into the cytoplasm for reuse.
44The CytoskeletonThe cytoskeleton is a network of protein fibers that crisscross within the cytoplasm.The cytoskeleton is made up of different types of fibers that help maintain a cell’s shape and can anchor the organelles or assist with their movement.
45Cell MovementCilia, tiny hairlike structures on cell surfaces and Flagella, large single projections from cells are involved in movement.
46Cilia and FlagellaCilia that line the respiratory tract sweep debris trapped in mucus out and cilia in the oviducts move eggs along.Sperm cells have flagella that move them to find and fertilize eggs.
47Mitochondria Structure Mitochondria are found in plant and animal cells.Mitochondria are bounded by a double membrane.The inner membrane is folded to form shelves called cristae.The folds project into the matrix an inner space filled with a gel-like fluid that contains enzymes, which are used to break down glucose products.
49Additional Mitochondrion Facts Mitochondria were originally prokaryotes.Mitochondria contain their own DNA and ribosomes.Mitochondria are only produced by other mitochondria.In humans and most multicellular organisms mitochondria are maternal inherited from the mothers egg.
50Mitochondria Function Mitochondria are often called the powerhouses of the cell.Mitochondria convert the chemical energy of glucose into the chemical energy of ATP.This cell process is called cellular respiration.
51Summary of Cellular Respiration Glucose is combined with oxygen and breaks down to carbon dioxide and water.The Overall Chemical Reaction:C6H12O6 + 6O2 6CO2 + 6H2O + EnergyGlucose + Oxygen Carbon Dioxide + Water + EnergyCellular respiration!
52Summary of Cellular Respiration Cellular respiration provides the energy to run cell processes.Three pathways called glycolysis, the citric acid cycle, and electron transport are involved.They allow the chemical bond energy from glucose to be slowly released and used to produce ATP.Altogether, 36 ATP molecules result from the breakdown of 1 glucose molecule.
53Summary of Cellular Respiration The first pathway (glycolysis) occurs outside mitochondria and breaks down six carbon glucose into two smaller three carbon molecules.The second pathway (citric acid cycle) occurs within the inner matrix, which contains the enzymes that continue the breakdown of the three carbon molecules.The third pathway (electron transport) occurs along the inner membrane folds called cristae where most of the ATP is produced.
54Summary of Cellular Respiration Figure 3.19 – Page 60