Structure and Function of the Cell

Cells make up all living things

Resolution is important for cell research

Cells are the basic unit of life Cells Tissues Organ systems Organs Organisms

CELL THEORY 1665 – Robert Hooke - cork compartments -cells 1674 – Leeuwenhoek observes living cells for the first time - animalcules 1838 – Schleiden determines all plants are made of cells 1839 – Schwann determines animals are made of cells 1850 – Brown discovers the dense centers of certain cells and names the nucleus 1855 – Virchow discovers cells make more cells

THREE POINTS OF THE CELL THEORY All living things are made up of one or more cells Cells are the basic unit of structure and function in living things Cells come from previously existing cells – NO spontaneous generation!

Classifying Cells Cells can be classified many ways. One way is to look at their complexity –Prokaryotes are very simple cells –Eukaryotes are more complex

There are two major types of cells:  Prokaryotes: literally means “before nucleus”  primitive single celled life, the first!  example: all bacteria  DNA lives in cytoplasm  no membrane bound organelles  extremely small (even for a cell!)

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Prokaryotes Vs. Eukaryotes Eukaryotes: - literally means “true nucleus” - DNA enclosed by the nuclear membrane - Can be single celled like protists (amoebas, paramecium) - Or can be part of a multicellular organism like: plants, animals or fungi

Prokaryotes Vs. Eukaryotes Eukaryotes: - significantly larger than prokaryotic cells - have many more organelles than prokaryotic cells - Protists, Fungi, Plants, Animals ALL have eukaryotiic cells.

All cells must perform certain tasks to stay alive Just how they go about it might be a little different depending on what organelles they have to work with and the environment in which they exist.

What must the cell do to survive?

Diversity in size, complexity, function

Study of the Cell: 1.Cells must regulate what enters and leaves the cell. 2. Cells must obtain and metabolize nutrients for the purpose of energy. 3. Cells must grow and reproduce. 4. Cells must synthesize, modify and ship proteins to their destinations.

Will talk about along the way 5. Cells must be able to store nutrients, isolate and digest damaged organelle and potentially harmful chemicals 6. Cells must be structured in a particular way and be mobile if necessary.

Regulating what goes in and out of the cell Cell Membrane

What are the needs of the cell? To build new structures (make proteins, carbs and lipids) To provide energy to build or to remove waste (when needed) To grow

Moving across the membrane – no energy required Diffusion – through the phospholipid bilayer Facilitated diffusion – through proteins that require no energy (channel proteins) Osmosis – transport of WATER through channel proteins

Active Transport – Energy required Movement across membrane goes through special proteins that require energy to work (ions) Vesicles – Exocytosis (out) and endocytosis (in) also require energy (movement of LARGE molecules)

Protein transport - Ions

Exocytosis (Golgi and vesicles)

Endocytosis (Phagocytosis)

Cells must obtain and metabolize nutrients for the purpose of energy Organelles used to obtain and metabolize energy –Plants Chloroplasts Mitochondria Cell membrane

Mitochondria and Chloroplasts Mitochondria are found in all cells –They create ATP from “food monomers” –The easiest one to use is glucose Chloroplasts are found in plant cells –They create the glucose that is used by the mitochondria

Obtaining energy: Plants Leaves are the organ, that contain cells that contain chloroplasts Create organic molecules using the sun’s energy

Cells containing chloroplasts

ONE chloroplast! Chloroplasts capture the sun’s energy  glucose Photosynthesis

Plants can create proteins and lipids too!

How do other eucaryotes obtain glucose, amino acids and lipids? Humans foods are broken down to monomers which are small and are passively transported across the CM Many protists use endocytosis, followed by digestion inside the cells (lysosomes fuse)

Animals digest carbs. proteins and lipids

Nutrients diffuse into cells Used for ATP or Building blocks mitochondria

Mitochondria Process: Cellular Respiration –JOB: extract energy from the C-H bonds (in organic molecules) and place it in ATP molecules –In the presence of oxygen 36 ATP/glucose molecule are made. When oxygen is not present (or in the absence of the mitochondria, only 2 ATP are made.

Purpose of vesicles (as related to cell membrane) To move food and hormones into the cell (endocytosis), These vesicles are called endosomes To move material out of the cell (exocytosis) –These vesicles are called secretory vesicles –To provide a “reaction location” that is separated from the cytosol (lysosomes, peroxisomes)

Cell Growth and Reproduction DNA- chromosomes duplicate and divide New cells formed

Cell Growth leads to…. Larger number of cells, cell differentiation

Cells must be able to synthesize protein

Cells must be able to modify and ship proteins (and lipids)

Cells need a support and highway system (cytoskeleton)

Some cells need motility (cytoskeleton)

Microscopes Tools –Objects used to improve the performance of a task Microscopes –Extend human vision by enlarging, with high resolution, things that might be impossible to see.

Light Microscopes Use light (photons) to view specimens –Two types Stereo (dissecting) microscope –40x – 70x magnification (in general) –3D view (two eye pieces) –Live specimens can be viewed, but often used to compare two things (ballistics, etc) Compound Light Microscope –Magnifies using two lenses – 1000x – 2000x –Thick objects must be sliced thin enough so that light passes through

Paramecium – Light microscope

Magnification vs. Resolution Magnification –Increase in an object’s apparent size Resolution –Minimum distance between two objects at which the objects can just be determined as separate. –No resolution in light microscopes beyond 2000x

Electron Microscopes A beam of electrons produces an enlarged image Higher magnification (up to 2,000,000x) and resolution (use electrons rather than photons) than light microscopes Always black and white (color is added by computer, electrons do not emit a color) Always,dead (specimen must be in a vacuum chamber so… no air)

Scanning EM Surface scanning 3D Gold coated and electrons are “fired” at the metal coating (metal emits other electrons and these are projected onto a photographic plate (100,000 – 200,000x)

Paramecium – SEM

SEM

Transmission Transmits electrons THROUGH a very thinly sliced specimen Magnetic lenses enlarge the impage Magnification 200,000x to 2,000,000x

TEM cross- section

Paramecium Organelles

Units of measure in Microscopy Metric system –Consists of base unit Length = meter (m) Mass = gram (g) Volume = liters (l) We will use units of length (micrometers and nanometers ) to describe the size of organisms

Prefixes Prefix prefix abbr unit = 1 x ____ meters Nanonnm10 -9 Microu or   m Millimmm10 -3 Centiccm10 -2 NO prefixA Angstrom10 -10