Cell Structure and Transport

Famous Scientists  Anton van Leeuwenhoek: “father of microscope”; noticed tiny organisms living in pond water  Robert Hooke: named the “cell” after rooms in a monasterty (observed them in cork)  Robert Browne: discovered the nucleus  Mathias Schleiden: stated all plants are made of cells  Theodore Schwann: stated all animals are made of cells  Rudolf Virchow: stated all cells come from other cells

Development of the Cell Theory  The scientists on the previous slide, in combination with some others, were responsible for the most important biological theory of modern science:  The cell theory states: 1. all living things are made of cells 2. cells are the basic unit of structure and function function 3. all cells come from existing cells by cell division division

Cell Types There are two categories of cells: Prokaryotic – have no nucleus and no membrane bound organelles (ex. Bacteria) Eukaryotic – have a nucleus and membrane bound organelles EukaryoteProkaryote

Plant vs. Animal Cells Organelles found only in plants: Chloroplasts Cell wall Vacuoles are much larger larger Organelles found only in animal cells: Lysosomes Vacuoles are much smaller smaller Animal Cell

Plant Cells Notice the rectangular or square shape of plant cells. You can see the thick cell wall, composed mostly of cellulose. You can also see circular regions. These are the nuclei. Cell Wall Nucleus Chloroplasts

Animal Cells Notice the circular shape of animal cells. Not all animals cells have this shape, but it is more common than not. Nucleus Cell membrane

Functions of Organelles Nucleus: controls the cell and contains the DNA (has pores in the envelope to allow things to come in and out) Chromosomes: contain genetic info. In the form of condensed DNA Cell wall: supports and shapes plant cells (anything can pass through it) Cell membrane: regulates what goes in and out (selective permeable) Cytoplasm: fluid that fills the space in cells

Vacuoles: store water (larger in plant cells) Mitochondria: break down glucose to make energy for cells Chloroplast: takes energy from sun and converts it into a usable form of energy in the form of glucose Ribosomes: assemble proteins (protein factories) Lysosomes: use enzymes to digest and get rid of wastes in the cell, as well as worn out cell parts

Other organelles: Golgi Apparatus: modifies, packages, and sorts materials Endoplasmic Reticulum: system of transport tunnels from nucleus to Golgi

Cell Transport

Structure of Cell Membrane The cell membrane is composed of a lipid bilayer. Because of its’ structure, it is selectively permeable, meaning it only allows certain substances in and out.

Notice the polar heads (water loving) and non- polar tails (water fearing)

Passive Transport vs. Active Transport  Passive transport – transport of materials from a higher to lower concentration. Energy is not required for this to occur.  Active transport – transport of materials from a lower to higher concentration. Energy is needed for this to occur. high low Weeee!! ! high low This is gonna be hard work!!

Passive Transport 3 types of passive transport:  Diffusion - transport of substances  Osmosis – transport of water  Facilitative Diffusion – transport with the help of carrier proteins (for molecules too large to pass through the membrane without help)

Diffusion Transport of substances (other than water) from areas of high to low concentration. Diffusion occurs until the molecules are distributed evenly throughout.

Diffusion Through Cell Membranes Molecules tend to diffuse across a cell membrane until equilibrium is reached (the same amount of solutes on both sides). For example: The capillary below is returning blood to the lungs, thus has a high concentration of carbon dioxide. The air sacs in the lungs have a lower concentration of carbon dioxide. Which way will the carbon dioxide go? bloodstream CO2 air sacs

Osmosis  The diffusion of water across a selectively permeable membrane (high to low concentration)

Oops! What is he doing here?

Osmosis Across a Barrier

Notice the water rises on the left side of the tube, as water moves from right to left. The sugar concentration is higher on the left, so water moves through the membrane until the solutions are about equal in terms of sugar concentration

There are 3 types of Solutions That Effect Osmosis:

Which one is hypertonic, hypotonic, and isotonic? Plasmolysis occurs as the cell shrinks. Cytolysis occurs when the cell bursts

Hypertonic, Hypotonic, or Isotonic?

ISOTONIC HYPOTONIC HYPERTONIC

Osmotic Pressure  This is the force exerted by osmosis that “pushes” water through a selectively permeable membrane to make the concentration of solutes the same on both sides.

There are many ways that cells combat osmotic pressure, to avoid bursting. 1. animal cells are bathed in blood (blood has a certain amount of proteins, sugars, salts, and other solutes, rather than being surrounded by pure water. 2. plant cells have turgor pressure exerted by their cell walls to help them keep their structure with varying amounts of water 3. Some organisms, such as the paramecium, have contractile vacuoles to pump out excess water.

Turgor Pressure  This is the force behind the cell walls of plants, which allows them to keep their shape. What happens to turgor pressure when plants are put in a hypertonic, hypotonic, and isotonic environment?

Facilitated Diffusion  Diffusion of molecules with the aid of carrier proteins, located in the cell membrane, from high to low concentration

Active Transport - Requires energy - Movement of molecules from low to high concentration. - There are two types: exocytosis and endocytosis. Endocytosis – takes materials into the cell (low to high concentration) Exocytosis – materials exit the cell (low to high concentration)

Types of Endocytosis A.Pinocytosis – for fluids B.Phagocytosis – for solids C.Using vessicles -

Examples of Phagocytosis (Endocytosis) Macrophage (white blood cell) engulfing bacteria Amoeba engulfing food.