Cells: Building Blocks of Life

Objective 2.0 Identify functions of organelles found in eukaryotic cells, including the nucleus, cell membrane, cell wall, mitochondria, chloroplasts and vacuoles.

The Inside Story Cells are so small that the details of their structure could not be seen until better methods of magnifying and staining were developed.

We now know everything inside a cell. From the structures covering the cells to the organelles inside them, they have structure that helps to keep the cells alive.

Eukaryotic cell- A cell that contains a central nucleus and a complicated internal structure.

Two types of eukaryotic cells. Plant cell Animal cell

Prokaryotic-A cell that does not have a nucleus or any other membrane- covered organelles; also called a bacterium.

Staphylococcus aureus

Gut bacteria

Organelles- tiny cellular structures that enable the cell to live, grow, and reproduce.

Cell membrane- the phospholipids layer that surrounds the cytoplasm, through which substances pass in and out of the cell.

Cell membrane

Cell Wall- The outermost layer of plants cells that is made of cellulose.

Plant cell wall

Nucleus -The largest and most visible organelle found in a eukaryotic cells; contains the DNA and serves as a control center for the cell.

Red and White Blood Cells

The job of a nucleus is to be the control center of the cell. The nucleus in a human cell has forty-six chromosomes. This stores the instruction of the cell's activity. The nucleus has a membrane called a nuclear envelope. The nucleus is like a vault. It contains the cell's DNA.

As you prepare to leave the nucleus, you spot a small object floating past. It is the nucleolus or little nucleus. For many years to function of the nucleolus remained a mystery to scientists. Today it is believed the it is the site of ribosome production.

Nucleolus-a small round body inside a cell nucleus, composed of protein and RNA and it makes ribosomes for the cell.

Nucleolus

DNA (deoxyribonucleic acid) - Heredity material that controls all the activities of a cell, contains the information to make new cells and provide instructions for making proteins.

Chromosomes-rod shaped cell structure that directs the activities of a cell and passes on the traits of a cell to new cells.

Cytoplasm- cellular fluid surrounding a cell’s organelles.

Cytoplasm is composed of 65% water, with as much as a billion molecules contained within the cytoplasm of one single cell. The cytoplasm contains enzymes, and dissolved nutrients like amino acids and sugars. The water allows for reactions to occur within the cell

DNA is contained in the cytoplasm of prokaryotes. Also in prokaryotic cytoplasm there are ribosomes, which produce proteins, such as enzymes and transport proteins.

Lysosome- A special vesicle (sack) in a cell that digests food particles, wastes and foreign invaders.

Each lysosome contains enzymes that break down large food molecules into smaller ones. These smaller food molecule are then passed on to the mitochondria, where they are “burned” to provide energy for the cell.

They are also responsible for digesting old cell parts. Think of them as the garbage men of the cell. They go around picking up waste and disposing of the waste.

The membrane that surrounds the lysosome keeps the enzymes from escaping and digesting the entire cell!

Vacuoles- Stores water and other materials.

Mitochondria- breaks down food molecules to make ATP (source of energy).

The power of the cell. Structurally, the mitochondrion has a double-layered, smooth outer membrane with inner folds called cristae, the inner membrane in which energy collecting chemical reactions takes place.

Chloroplasts- Makes food using the energy of sunlight. This process is called photosynthesis.

Endoplasmic Reticulum- Makes lipids, breaks down drugs and other substances, packages up proteins for release from the cell. Two types - smooth and rough.

The rough endoplasmic reticulum (rough ER) is a series of folded sheets and interlocking channels that form something that resembles a maze. Rough ER is called 'rough' because of its exterior coating of ribosomes. These ribosomes, scattered over the outside of rough ER.

Ribosomes- the site where amino acids are hooked together to make proteins.

Golgi Body Complex- Processes and transports materials out of the cell.

Moving Small Particles Materials enter and leave a cell by one of these methods: Diffusion, osmosis, active transport, passive transport, endocytosis and exocytosis.

Diffusion- is the process by which molecules of a substance move from areas of higher concentration to areas of lower concentration of that substance.

Here’s an example.

Let’s test this out Let’s perform a few experiments to find out how it works. I have a air freshener that I will spray at the front of the room. The person at the back of the room will tell me when he/she smells the scent.

Experiment #2 I will drop some food coloring into a glass of water and watch what happens. Can you explain your observation?

Osmosis-is the passage of water from a region of high water concentration through a semi- permeable membrane to a region of low water concentration.

Using the definition of osmosis, tell me why you shouldn’t drink salt water no matter how thirsty you are?

Answer The concentration of water outside is lower the inside of the cell. This is because there are salt molecules taking up space in the water. This means that there are fewer water molecules. The water leaves the cell, and the cell starts to shrink. If too much water leaves the cell, the cell dries up and dies.

Passive transport- is a form of diffusion or osmosis in which materials move across a membrane without using the cell’s energy.

Sometimes, large molecules cannot cross the plasma membrane, and are "helped" across by carrier proteins - this process is called facilitated diffusion.

Facilitated Diffusion is a FORM of ACTIVE TRANSPORT AND THEREFORE REQUIRES NO ENERGY INPUT.

Active Transport - this type of transport requires that the cell use energy, because substances are moving against the concentration gradient.

Endocytosis - cell takes in large particles by engulfing them.

Exocytosis - cell gets rid of particles, opposite of endocytosis.

The End.