Cell Biology

Cells

• Definition: The smallest most basic unit of all living things that is still considered alive.

• Examples of cells: bacteria, muscle cells, nerve cells, fatty tissue is made of fat cells, skin, bone marrow, pancreas cells…..

Gametes (Sex Cells)

• Egg • Sperm

Classification of Cells

• Prokaryotic • Do not have membrane bound organelles (structure within a cell that are surrounded by a membrane).

• Most notably, no nucleus.

• Make up single celled organisms called Bacteria

• In fact, the only prokaryotic cells present today are Bacteria cells

Examples of Prokaryotic Cells

Billion year old bacteria

Rod Shaped Bacteria

Classification of Cells

• Eukaryotic: • Do have membrane bound organelles within the cell.

• So, do contain a nucleus.• Make up both single

celled and multicellular organisms.

• Examples of eukaryotic organisms include: animals, plants, amoeba, paramecium….

Eukaryotic Cell detail: note the many membrane bound organelles

Examples of Single Celled Eukaryotic Cells

Paramecium Diatom Algae

Viruses

• Not necessarily living: not a cell because it lacks the ability to replicate on it’s own.

• Made up of a protein coat (shell) surrounding a nucleic acid molecule (either DNA or RNA).

• Function: inject DNA/RNA into cell and turn cell into a virus factory that makes many copies of the virus.

More Viral Structures• Microscope picture of WSSV virus: kills

shrimp. (source: Wageningen University, Laboratory of Virology)

•Ebola Virus

Virus that causes pink eye

Bacteriophage

Compare/Contrast Prokaryotic, Eukaryotic Cells and Viruses

• Q: Which have an outer membrane?

• A: Prokaryotic/Eukaryotic cells

• Q: Which have a protein coat?

• A: Viruses• Q: Which have DNA?• A: All• Q: Which rely on other

cells for replication?• A: Viruses

• Q: Which have membrane bound organelles?

• A: Eukaryotic cells• Q: Which can live on their

own?• A: Prokaryotic/Eukaryotic

cells• Q: Which can cause

disease?• A: All

Cell Membrane

• Structure of all cells that regulates what enters and leaves the cell.

• Selectively permeable:

• Some chemicals can pass through membrane while others cannot

Structure of Cell Membrane• 1. Phospholipid bilayer: fluid layer• 2. Proteins imbedded in the lipid bilayer act as pumps/channels, receptors, and

identification markers• 3. Cholesterol attaches to phospholipid tails, inhibiting movement. Result is cell

membrane is less fluid.

Function of Cell Membrane

• It is a barrier between the interior of the cell and its exterior environment.

• Both the internal and external environment of cells are liquidy: water solvent with various solutes such as proteins, gases, ions, sugars, amino acids, nucleotides.

Movement of Substances across the Cell Membrane

• Passive Transport:• Does not require

cellular energy• Types of Passive

Transport include diffusion and osmosis

• Active Transport• Do require cellular

energy• Types of active

transport include movement through a protein pump, endocytosis, and exocytosis

Passive Transport: Diffusion

• Definition of Diffusion:• When molecules move

from an area of greater molecule concentration (conc.) to an area of lesser molecule concentration.

• Example:• Perfume diffuses through

the air. • The perfume molecules

move from an area of greater perfume molecule conc. to an area of lesser perfume conc.

• Another (more gross) example:

• Someone farts…..

Passive Transport: Diffusion Examples

• 1: • 2:

Passive Transport: Diffusion Examples

• 3:

•Gas exchange in our lungs is an example of diffusion in our bodies.

• Water absorption in our skin when we swim or take a bath is also an example of Diffusion in our bodies (as water diffuses into our skin, the skin puffs up; however, because it is attached to the inner layer of skin it wrinkles)

Passive Transport: Osmosis

• Definition of Osmosis:

• When water molecules diffuse across a selectively permeable membrane.

• Examples:• When there is a higher

water concentration outside a cell than inside a cell, the water molecules will diffuse across the cell membrane into the cell

• When water passes through a plastic bag with holes that are only big enough for the water to pass through but nothing else.

Passive Transport: Osmosis Example

Passive Transport: Osmosis Example with RBC

Active Transport: Endocytosis

• Using cellular energy to actively take something into a cell.

Active Transport: Exocyctosis

• Using cellular energy to actively expel something from a cell.

Secretion of Proteins• 1. Proteins are

made at the Ribosomes.

• 2. From there they travel through the cell in the Endoplasmic Reticulum.

• 3. A vesicle pinches off from the Endoplasmic Reticulum and travels to the Golgi Apparatus and fuses to it.

• 4. The proteins are modified in the Golgi Apparatus

• 5. Then a vesicle pinches off from the endoplasmic reticulum, travels to the cell membrane and fuses to it.

1.2.

3.

4. 5.

Ribosomes

Examples of Protein secretions

• Saliva

• Venom in snakes and scorpions

• Digestive enzymes in our stomach and pancreas

• Neurotransmitters that carry messages between our nerve cells

• Poisons in spiders and stinging jellyfish

• Enzymes in tears

Energy in cells: involves two organelles

• Photosynthesis: Chloroplasts in plant cells

• Organisms that make their own food through photosynthesis are called autotrophs.

• Cell respiration: Mitochondria in plant and animal cells

• Organisms that need to consume other living things for food are called heterotrophs.

1. Sunlight captured by chloroplasts

2. Chloroplasts make glucose

(cellular food)

3. Organisms eat plants, or other animals

that eat plants, and take in glucose

4. Glucose diffuses into a cell through a membrane protein

5. Glucose broken down in mitochondria

to release cellular energy (ATP)

Photosynthesis

• Equation:• 6 CO2 + 6 H2O C6H12O6 + 6O2

• Sunlight Energy

• The light energy from the sun gets trapped into a molecule of glucose.

• Where do the reactants come from?• Where do the products end up?

Cell Respiration

• C6H12O6 + 6O2 6 CO2 + 6 H2O

• ATP• When glucose is broken down in the

mitochondria, the energy that was trapped in the glucose molecule is released as cellular energy.

• The cell uses cellular energy for growing, moving, reproducing, making proteins, building biomolecules, digesting biomolecules.