The Structure and Function of Cells Cell Theory Parts of a cell Organelles Cell Diversity Crossing the Membrane

The Cell Theory 4 Parts –Cells are the basic unit of life –All organisms are made up of one or more cells –All cells carry out life processes –All cells arise from pre-existing cells

Who is Responsible for this cell theory???? A whole bunch of dead scientists….. –Anton Von Leeuwenhoek –Robert Hooke –Matthais Schleiden –Theodor Schwann –Carolis Linnaeus

The Parts of a Cell (organelles) Cell Membrane (Found in Plant and animal cells)

Fluid Mosiac Model Theory that scientists have created to explain how the cell membrane works Theory states that there are 2 layers of molecules called a bi-layer - these molecules are called phospholipids. Structurally similar to a sandwich Each individual phosphoplipid has a head and a tail which is hydrophobic and hydrophilic……….

The phospholipid

STOP!! BIG WORDS!!!! Hydrophobic: Hydro = Water ; Phobic = afraid The tail of the phopholipid is hydrophobic Hydrophilic: Hydro = Water ; Philic = loving The head of the phospholipid is hydrophilic Millions of these molecules line up together to form a cell membrane!

What is the cell membrane for? Controls transport into/out of a cell Holds the cell together-keeps all the “pieces” such as organelles and cytoplasm inside Semi-permeable = Gateway: allows only certain material to pass through Phospholipid Head Tail

Cell Membrane

Membrane looks big? Picture this……. It would take 10,000 membranes to equal the thickness of one sheet of paper!!!

Cell Membrane Proteins Proteins are stuck throughout the cell membrane - but what are they there for? Let molecules into and out of the cell THE ENFORCER Is there a name for the process of allowing various substances to travel across the membrane? YES!!

DIFFUSION (2 Types) Diffusion: causes many substances to travel across the membrane (NOT INCLUDING WATER!!) from a high to low concentration without the use of energy. Think of a balloon popping.. What happens? Facilitated diffusion: requires the use of proteins in the cell membrane to carry material into and out of the cell (NOT INCLUDING WATER!!) from an area of high to low concentration without the use of energy

Keep in mind…... Not all substances can pass through the cell membrane!!! Only certain substances when needed…….this is called SELECTIVE PERMEABILITY …. Know what this means……

Osmosis and Active Transport Osmosis: Osmosis is basically the same as diffusion with the exception that it deals only with water passing through the membrane from an area of high to low concentration. Active Transport is similar to facilitated diffusion with 2 exceptions. 1 - Active transport requires energy 2 - Active transport brings substances from a low to high concentration

Osmosis – Where is there more water in this example??

Active Transport vs. Diffusion

Active Vs. Passive Transport Active Transport –Requires Energy –Go from Low to High Concentration –Use Proteins Passive Transport –No Energy –Go from High to Low –May or may not use proteins

Passive vs. Active Transport

The effects of osmosis on cells HypotonicIsotonicHypertonic Different solutions have different impacts on cells…

Hypertonic, Hypotonic, Isotonic Water always tries to balance itself out..so….if there is less water outside of the cell than inside than it can be inferred that water will move out of the cell…..this is called a hypertonic solution. If the concentrations are reversed and water flows into the cell…this is called a hypotonic solution. If there are equal concentrations in and out of the cell, this is an isotonic solution.

Think about this……. You have two identical pitchers side by side, one filled with exactly 2 quarts of water, the other filled with 2 quarts of Kool- aid……….which has more water?? WHY???

Cell Wall (Plant cell only) Cell Wall

Cell wall - What is it? Found only in plant cells outside of the cell membrane Composed mainly of cellulose (type of carbohydrate)

What is the Cell Wall for? Helps to maintain the shape of the plant and keep the structure of the plant. Turgor pressure in the cells of plants prevents the leaves from drooping over. Holes in the cell wall allow molecules to pass through…….these holes are called PLASMODESMATA

PLASMODESMATA

The Nucleus Brain of the cell If you take the nucleus out…the cell is dead. It tells every part of the cell what to do. Not all cells have a nucleus….these are called prokaryotes. Cells with a nucleus are called eukaryotes.

What’s inside the nucleus? All the stuff needed and used in cell reproduction. This stuff is your DNA (deoxyribonucleic acid) This is made up of nucleic acids – (we’ll talk about that later) DNA tells the cell what yo do and helps to make and the best decisions for the survival of the cell.

The Nuclear Membrane The nuclear membrane is a membrane around the nucleus that holds it together helping to retain the genetic information inside the nucleus. Let’s take a look at what is inside the nucleus.

Chromatin Chromatin is made up of DNA inside the nucleus When the cell is going to divide, the chromatin condenses into what scientists call chromosomes. These are important for passing on your genetic information.

Nucleolus Looks like a small, dark area inside the nucleus. This contains protein and RNA… We’ll talk much more about this in Genetics

Ribosomes Protein builders of the cell Found either free floating in the cytoplasm (fluid that fills a cell) or attached to the endoplasmic reticulum. Proteins made are used inside and outside of the cell for growth and repair.

Endoplasmic Reticulum (ER) 2 Types - Rough and Smooth ER Used for transport in the cell

Golgi Apparatus Made out of a bunch of flattened sacs. Think of a stack of pancakes. It is the packaging center of the cell. Like a mailroom It takes simple molecules and combines them to form more complex molecules.

It will them package up the large molecules into sacs called vesicles. These vesicles are then released into the cytoplasm and then eventually released outside of the cell.

Mitochondrion POWERHOUSE OF THE CELL Where cells breakdown molecules for energy (ATP) Site of respiration in a cell Why is the inner membrane folded? To increase surface area to produce more energy

Chloroplast (Plant cells only) Carry out photosynthesis - take energy from the sun and make food. This food comes in the form of sugars and starches. Check it out……….

Photosynthesis

Vacuole Storage compartments in cells Some contain food, others hold oil, some hold wastes They are huge in plant cells and much smaller in animal cells The vacuole basically holds things that the cell might need, like a backpack

Turgor pressure The vacuole helps to maintain turgor pressure so that plants can remain upright and not droop over.

Lysosomes Digest “food” inside the cell and release smaller molecules so they may be used by such organelles like the mitochondria for energy. It will also break down any other dying organelles Have potential to kill the cell if they puncture the cell membrane

Lysosomes breaking down organelles within a cell.

Centrioles Only in animal cells Used during cellular reproduction

Lets put ‘em all together Animal CellsPlant Cells

Animal Cell Golgi Apparatus Lysosome Mitochondria Vacuole Endoplasmic Reticulum Nucleus Nucleolus Cell Membrane

Animal Cells-Drawing

Plant Cells Where do they come from? Plants of course……DUH!! All plant cells have the same characteristics

Plant Cell Vacuole Chloroplast

Major Differences between Plant and Animal Cells Plant Cells Plants have a cell wall Contain chloroplasts Have a large vacuole Do NOT have centrioles Animal Cells No cell wall No Chloroplasts Small vacuoles Have centrioles

One more thing to worry about… Prokaryotic vs. Eukaryotic cells Prokaryotes NO NUCLEUS Have a cell membrane and cytoplasm…but no organelles Carry out life processes Eukaryotes HAVE NUCLEUS Have organelles contained within the cytoplasm Carry out life processes

What are methods of cellular movement???

Pseudopods Pseudopods (false feet)- like throwing a grappling hook and pulling yourself along.

Cilia Cilia- tiny beating hairs that act like oars Example- Paramecium

Flagella Flagella- whip like tail (sperm cell)