Cells: Life in Balance

9-11 LS 1C: A cell contains specialized parts for determining its essential functions, such as regulation of cellular activities, energy capture and release, formation of proteins, waste disposal, the transfer of information, and movement.

9-11 LS 1D: the cell is surrounded by a membrane that separates the interior of the cell from the outside world and determines which substances may enter and which may leave the cell.

Why Does “Balance” Matter? Consider for a moment the

importance of a space suit for astronauts to walk in space. Without the space suit, or a barrier between an “internal” and “external” environment, the astronauts would die.

Living organisms must maintain certain conditions in their bodies to stay alive.

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Homeostasis Balance….under normal conditions, it is

an intricate, dynamic state that our bodies take care of with little conscious effort.

To accurately summarize what homeostasis really means, the word “balance” is the perfect description.

Definition: The process of maintaining a constant internal environment despite changing external conditions. Examples: Concentration of water, gases, waste, and temperature regulation (to name a few)

What is the primary unit of life? The Cell: It isn’t just a bag of goo, it is

an elaborate, efficient machine with specialized parts that enable us to live.

What do they look like?

Cell Theory: Why Do Cells Matter?

1. The cell is the basic unit of structure and function in living things.

2. All organisms are composed of cells and/or cell products.

3. All cells come from other cells.

Types of cells Cells are organized by how simple or complex

they may be: A.Prokaryotes: Cells that lack membrane-

bound organelles B.Eukaryotes: Complex cells that contain

membrane-bound organelles. 1. These organelles are smaller structures within

cells that have specific roles to keep the cell alive. Just like the organs in animals.

Cells are like tiny organisms

Organisms are composed of organ systems, and those organ systems are composed of organs. Eukaryotic cells are composed of organelles that have a specific Job that each must do to keep the cell alive.

Organelles 1. Cell Membrane: The outermost barrier of the

cell that separates the internal environment from the external environment.

Analogy: This is like our skin. It is a barrier to keep

certain things in, and certain things out. 1. Also called the “plasma membrane”. 2. It is “selectively permeable”

Allows only certain substances to pass through: based on size, ionic charge and concentration (inside vs. outside).

Organelles

2. Nucleus: This is the control center of the cell that regulates all cell functions and activities. 1. Contains the DNA (the instructions). Analogy: It is like our brain because it

controls all functions & activities.

Organelles 3. Ribosomes: There are hundreds of these

round structures throughout each cell. They are responsible for manufacturing proteins. A. Proteins are a primary building material of cells. B. Proteins also control the functions called

metabolism in our bodies. C. The ribosomes reassemble the amino acids

from the food you ate into new proteins. Analogy: Ribosomes are like our cells. They put the

correct pieces together to make something

Organelles

4. Mitochondrion: These organelles are where energy from the food you eat is broken down and released for the cell to use.

A. There are dozens, sometimes hundreds of these in each cell.

B. These use glucose from the food you eat to produce energy.

Analogy: These are like the digestive system of the cell that break down “food” to release energy.

Organelles

5. Endoplasmic Reticulum (ER): membranes in the cell that transport substances made by the cell (proteins and lipids) A. Rough ER has ribosomes attached – the proteins

made here are for transport out of the cell B. Smooth ER does not have ribosomes attached

(specializes in making and transporting lipids) Analogy: The ER is like our blood vessels that

transport materials.

Organelles

6. Golgi Apparatus: receives proteins from the ER and then packages them up and distributes them where they need to go Analogy: Like our blood cells which bind to

oxygen to distributes it to the cells

Organelles

7. Centrioles: rod-shaped organelles that help move chromosomes during cell division Analogy: They are like your muscles that

move parts of your body.

Organelles

8. Cytoplasm: a term for all of the material between the nuclear membrane and the cell membrane A. Cytosol is the liquid portion of the

cytoplasm Analogy: This is kind of like the fluid and

goo in between our cells.

Animal Cells

Plant cells contain the same organelles as animal cells, plus 3 specialized ones:

1. Chloroplasts: These are the site

of photosynthesis (conversion of sunlight energy into sugar-glucose). A. Each plant cell contains numerous

chloroplasts. Analogy: These are kind of like solar

panels (they aren’t analogous to anything in a human)

Plant Cell Differences

2. Vacuole: fluid filled storage sac in the plant cell that regulates water concentration and the internal pressure of the cell.

Analogy: Kind of like our kidney’s do for our body

3. Cell Wall: This sturdy, rigid layer surrounds the cell membrane.

Analogy: They are like our skeleton; provide structure and support

Plant Cells