CELL STRUCTURE AND FUNCTION

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Body Organization

• The fundamental units that make up all living things are called cells.

• When cells cluster together and perform the same function, they are called tissues.

• When tissues cluster together and perform the same function, they are called organs.

• Organs cluster together to form organ systems, which result in the total organism.

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Organization

Cells Tissues Organs

Organ systems Organism

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All Cells On Earth

• Are enclosed in a membrane that maintains internal conditions different from the surroundings.

• Have DNA as the genetic material.

• Can interconvert forms of energy.

• Can interconvert chemical materials.

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Every cell has three things in common:

• Metabolism (using up oxygen and sugars).

• Responds to its environment

• Capable of maintaining homeostasis within itself and within the body.– HOMEOSTASIS is maintaining a balanced

internal environment, such as temperature, pH, glucose levels, etc.

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CELL ORGANIZATION

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CYTOPLASM

• Jelly-like substance in the cell around the organelles. • This is where many of the chemical activities (cellular

metabolism) of the cell occur.• Cytoplasm contains mostly water and things dissolved in

water (sugars like glucose, and energy molecules =ATP)

Cytoskeleton: made up of long protein fibers that extend throughout cytoplasm.

1) Maintains cell shape 2) Movement

a) muscle cell contractionb) moving organelles within the cellc) moving the cell itself

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ORGANELLES

• Small structures (miniature organs) that occur within the cell and have various functions.– PLASMA MEMBRANE– NUCLEUS– MITOCHONDRIA – ENDOPLASMIC RETICULUM – GOLGI COMPLEX– VESICLES– CILIA AND FLAGELLA

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PLASMA MEMBRANE

• Surrounds the entire cell.

• Functions of the Plasma Membrane:– Plasma membranes are selectively

permeable. This means that the plasma membrane allows some substances to enter or leave a cell more easily than others.

– Communication with other cells and the environment

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PLASMA MEMBRANE

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NUCLEUS

• Usually the largest structure in a cell.

• Functions of the nucleus: Stores DNA (genetic material that makes up chromosomes). Our genes are on the chromosomes) The majority of genetic material within the cell is contained in the nucleus

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MITOCHONDRIA

• Cells have hundreds of mitochondria.• Function of mitochondria is to make ATP

(energy molecules).• NOTE: Mitochondria must have OXYGEN to

convert nutrients to ATP for energy. Therefore, the mitochondria are the organelles that carry out cellular respiration, converting the chemical energy of foods such as sugar into the chemical energy of a molecule called ATP.

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CELL ORGANIZATION

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RER

• ROUGH ENDOPLASMIC RETICULUM (endoplasmic = within cytoplasm; reticulum = network; rough = surface of membrane covered with RIBOSOMES.

• The function of ribosomes (and therefore, function of RER) is to make proteins.

• Ribosomes make proteins out of amino acids.

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• The messenger RNA carries the blueprint of the DNA’s amino acid sequence into the cytoplasm; it then carries it into the ribosomes within the RER.

• The ribosome has the RNA that translates the blueprint into an exact copy of the original DNA strand, and the protein is formed within the ribosome (like a protein factory).

• The protein is then taken out and carried through the canals of the reticulum like a boat going down a canal in Venice. The protein then floats into the Golgi complex, where it will be packaged for shipment like a Fed-Ex center.

• Some of these proteins will be used to make enzymes. Enzymes are required for the cell to undergo various reactions. Elevated body temperatures may denature enzymes.

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Golgi Complex

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GOLGI COMPLEX

• The Golgi apparatus is a complex system of membranous channels and saccules continuous with the plasma membrane.

• Function of Golgi complex: – Packages the proteins made by the RER

and sends them where they need to go (like a UPS center!)

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RER to Golgi Complex

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SMOOTH ENDOPLASMIC RETICULUM

• No ribosomes

• Function of SER– Involved in metabolism (making use of

carbohydrates (sugars) and lipids (fats).– Stores calcium (necessary for every cell)– Detoxifies harmful substances (alcohol,

drugs, etc)• NOTE: in CSI, when they suspect poisoning,

they first look at the SER in the liver.

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VESICLES

• Spheres of membranes with something inside.– LYSOSOMES: contains digestive enzymes to

dissolve bacteria. When a bacterium is discovered within a cell, a lysosome bubble will fuse onto it and release its contents in an effort to dissolve the invader. If there was a defect in the lysosome of a white blood cell, the bacteria could accumulate within the cell and kill a person by infection.

– TRANSPORT VESICLES: moves material from RER to Golgi complex, or from Golgi complex to cell membrane, etc.

– STORAGE VESICLES

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Vesicles

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CILIA AND FLAGELLA

• Some cells have hair-like structures that move the cell.

• The longer structures are called flagella and shorter ones are cilia.

• Sperm cells, for instance, have flagella, which they use to move from one place to another.

• Cells in our trachea have cilia which can move mucous along the top of the cell (when you cough up mucous).

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Cilia

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Flagella

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Flagella Movement

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SUMMARY OF CELL FUNCTION

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SUMMARY OF CELL

FUNCTION

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SUMMARY OF CELL FUNCTION

• Each cell is near a blood vessel, which gives the cell nutrients it needs and takes products out of the cell to distribute to the rest of the body.

• The nucleus has DNA which tells the ribosomes what kind of proteins to make at the moment.

• The ribosomes get the amino acids from the bloodstream to build the protein molecule.

• The protein is taken to the Golgi complex, where it is packaged and sent to a storage vesicle.

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SUMMARY OF CELL FUNCTION

• The cytoskeleton fibers move the vesicle to the plasma membrane where it is released from the cell and picked up by the bloodstream and taken to where it is needed in the body.

• The bloodstream drops off sugars to the cell, which are taken to the mitochondria to be broken down into ATP, which is the energy molecule used to fuel all the functions of the cell.

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Cellular (aerobic) Respiration

• A process whereby cells use oxygen, produce carbon dioxide, produce energy, and form ATP.

• Breathing involves the lungs supplying oxygen to our cells and removing carbon dioxide. We often use the word “respiration” instead of breathing. Respiration refers to an exchange of gases: an organism obtains oxygen and from its environment and releases carbon dioxide as a waste product.

• Respiration can also apply to an individual cell when it harvests energy from food molecules; this is called cellular respiration.

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Breathing and Cellular Respiration

• Breathing and cellular respiration are closely related.

• As a gymnast goes through her routine, her lungs take up oxygen from the air and pass it to her bloodstream.

• The bloodstream carries the oxygen to her muscle cells.

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Breathing and Cellular Respiration

• Mitochondria in the muscle cells use the oxygen in cellular respiration, converting energy from glucose to generate ATP, which the cells then use to contract.

• Simultaneous contraction of thousands of cells, precisely controlled by the nervous system, makes the gymnast’s body move.

• The gymnast’s bloodstream and lungs also perform the vital function of disposing of the carbon dioxide waste produced by cellular respiration. 32

Energy

• Our body cells require a continuous supply of energy just to stay alive-- to keep the heart pumping blood, to breathe, maintain body temperature, and digest food.

• These and other life-sustaining activities use as much as 75% of the energy a person takes in as food during a typical day.

• Whether you are sleeping or active, your cells are busy with cellular respiration, producing ATP just to maintain your body.

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Riding a Bicycle

• 514 calories an hour

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Running

• 865 calories an hour

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Walking

• 200 calories an hour

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Cell Surfaces

• Protect, support, and join cells together

• To function in a coordinated way as part of a tissue, the cells must have junctions, structures that connect them to one another.

• Animal cells are embedded in a sticky layer that helps hold the cells together in tissues and provide protection and support as well. This allows contact from one cell to another.

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Cell Walls

• Plant cell walls consist of cellulose fibers embedded in a matrix of polysaccharides and proteins.

• Plant cell walls are multilayered structures. • Wood is primarily composed of plant cell

walls. • Plant cell walls protect plant cells but they

are still a layer that is permeable to selected substances.

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Rate of Cell Division

• The rate of cell division is close to the rate of cell death.

• 200 billion red blood cells die every day, so 200 billion red blood cells have to be made every day.

• Too few = anemia; too many is also a problem.• So, the body needs to do two things:

– Control the rate of cell division– Control the rate of cell death

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Inner Life of a Cell

• Inner Life of a Cell• http://www.youtube.com/watch?v=yKW4F0Nu-UY

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