Unit 4: Cell Biology and Energy Processes

The history…

• A long time ago, before microscopes were invented, people had no idea what caused sickness.

Superstition…

• They thought that illness was caused by curses and supernatural spirits.

Leeuwenhoek and Hooke

• In the 1600’s Leeuwenhoek observed microorganisms in water.

• At the same time Hooke was observing cork samples under a microscope.

What is a microscope?

• It is an instrument used to observe small objects.

• There are two main kinds:

• compound light microscope

• electron microscope

Light microscopes…

• use a series of lenses to magnify objects.

• Maximum magnification= no more than 1500X.

• It produces images like the one you see on your right of a microorganism.

Electron microscopes…

• were developed in the 1930’s and use a beam of electrons rather than light.

• Maximum magnification: 500,000X.

• It produces images like the one on the right.

Cell Theory

1. All organisms are composed of one or more cells.

2. The cell is the basic unit of structure and organization of organisms.

3. All cells come from preexisting cells.

Two Basic Cell Types

• Prokaryotic cells do not have membrane-bound organelles (e.g.: Nucleus).

• Eukaryotic cells contain membrane-bound organelles.

Orga-who?

• Organelles are small specialized structures found in cells.

• Bodies have organs; cells have organelles.

Cell Wall

• The cell wall is a fairly rigid structure located outside the plasma membrane that provides additional support and protection.

Nucleus

• The central membrane-bound organelle that manages or controls cellular functions

• Contains DNA

Nucleolus

• prominent organelle found in nucleus which produces ribosomes.

Ribosomes

• sites where the cell produces proteins

Cytoplasm

• a clear, gelatinous fluid inside the cell.

Endoplasmic Reticulum

• is the site of cellular chemical reactions and is arranged in a series of highly folded membranes in the cytoplasm.

• Rough ER has ribosomes.

• Smooth ER does not.• (Lipids are also made at

the smooth ER)

Golgi Apparatus

• is a flattened stack of tubular membranes that modifies proteins. It sorts proteins into packages and packs them in membrane-bound structures called vesicles. to be sent out to the appropriate destination.

Vacuoles

• are membrane-bound components used for temporary storage of materials.

Lysosomes

• are organelles that contain enzymes and digest excess or worn out organelles, food particles, and engulfed viruses or bacteria.

Chloroplasts

• capture light energy and convert it into chemical energy (photosynthesis).

• Make plants green

Mitochondria

• are membrane-bound organelles that transform food into energy for the cell.

• Responsible for aerobic cellular respiration

The Cytoskeleton

• is a recently discovered cell support structure.

• It is made up of hollow structures called microtubules (above) and microfilaments (below).

Centrioles

• play an important role in cell division.

Locomotion of Cells

• Cilia are hair-like structures used for movement.

• Flagella are tail-like projections that are used whip-like motions for movement.

The Plasma Membrane

• is the flexible boundary between the cell and its environment.

• Lipids have a polar head and a non-polar tail

Parts of the Plasma Membrane• phospholipids

have a glycerol backbone, two fatty acids chains and a phosphate group.

Bilipid layer

• The lipids have a side that likes water (hydrophilic) and a side that hates water (hydrophobic). So it naturally forms a bilayer that keeps its hydrophobic parts hidden from water and its hydrophilic parts touching water.

Transport Proteins

• move needed substances or waste materials through the plasma membrane.

• This helps to make the membrane selectively permeable.

Cellular Transport

• Osmosis is diffusion of water across a semi-permeable membrane.

Solutions…

• isotonic = solution in which equal concentration inside and outside of cell.

• hypotonic = less ions in solution than cell (more water on outside, water floods cell)

• hypertonic = more ions in solution than cell (less water outside, water comes out)

Passive Transport

• movement of particles across a membrane that requires no energy.

• When it uses no energy but does require using a membrane protein it is known as facilitated diffusion.

Active Transport

• is movement across the membrane that requires energy.

• This happens when molecules are being moved against the gradient.

Transport of Large Molecules

• Endocytosis is a process by which a cell surrounds and takes in material from its environment.

• Exocytosis is the expulsion or secretion of materials from a cell.

Cell Growth and Reproduction

• The bigger a cell gets, the smaller its surface area to volume ratio becomes.

• If a cell became too big it would take too long for wastes from the middle to make it all the way out through the membrane.

• Also it would take way too long for nutrients to reach from the surface all the way to the middle.

Volume vs. Surface Area

• 6cm2 : 1 cm3 = 6 • 24cm2 : 8cm3 = 3• 96cm2 : 64 cm3 = 1.5

Chromosome

• Two identical chromatids (sisters) are held together by a centromere.

• The tips are called telomeres.

The Cell Cycle

• is the sequence of growth and division of a cell.

Interphase

• The majority of a cell’s life is spent in the growth period known as interphase.

• DNA gets duplicated (copied) during this time.

Mitosis

• is the process by which two daughter cells are formed, each containing a complete set of chromosomes.

Step 1. Prophase

• It is the longest step.• The long stringy

chromatin coils up into chromosomes.

• The nucleus disappears; the nuclear envelope and nucleolus dissolve.

• The centrioles migrate to opposite poles and the spindle forms.

Step 2. Metaphase

• The doubled chromosomes become attached to the spindle fibers by their centromeres. The chromosomes are pulled by the spindle fibers to the middle (equator).

Step 3. Anaphase

• The centromeres split apart.

• The microtubules of the spindle fibers shorten.

• The sister chromatids separate.

Step 4. Telophase

• Chromatids reach the opposite sides (poles) of the cell.

• Chromosomes unwind into chromatin.

• Spindle breaks down.• The nuclear envelope

and nucleolus reform. • A new double membrane

begins to form between the two nuclei.

Cytokinesis

• After mitosis, the cell’s cytoplasm divides during this stage.

• In animals, the cells simply pinch off.

• In plant cells a cell plate is laid down and the plasma membrane and cell wall form on either side of it.

Energy Processes

• There are three major energy process that we will study in the cell:

1. photosynthesis

2. cellular respiration

3. fermentation

Photosynthesis…

• the process that uses the sun’s energy to produce simple sugars

6CO2 + 6H2O + (light) → C6H1206 + 6O2

(carbon water energy glucose oxygen

dioxide)

Cellular Respiration…• is the process by which mitochondria break

down food molecules to produce ATP.• ATP stores energy in the form of chemical

bonds

• Can be aerobic (needs O2) or anaerobic (doesn’t need O2)

• C6H1206 + 6O2 → 6CO2 + 6H2O + 36 ATP (energy)

Anaerobic respiration (Fermentation)

• There are two types:

lactic acid fermentation

alcoholic fermentation

Lactic Acid Fermentation

• Happens in your muscles during exercise

• Is responsible for the “burn” you get when exercising (acid)

• Produces small amounts of ATP without O2

Alcoholic Fermentation

• Yeast and other bacteria do this instead of lactic acid fermentation

• Produces ethanol (alcohol) instead of lactic acid

• Also produces CO2, which is what makes breads rise

Respiration…

Aerobic Respiration

• 36-38 molecules of ATP per sugar molecule

• Requires Oxygen

Anaerobic Respiration

• 2 molecules of ATP per sugar molecule

• Does not require Oxygen