Section 2: Looking Inside Cells

7.1.b Students know the characteristics that distinguish plant cells, including chloroplasts and cell walls.

7.1.c Students know that the nucleus is the repository for genetic information in plant and animal cells.

Enter the Cell

• Organelles- carry out specific functions within a cell

• Cell Wall- a stiff wall that surrounds the membrane giving the cell a rigid boxlike shape

• Key concept: “The cell wall helps to protect and support the cell.”

• In plants the cell wall is made of cellulose• Cell wall is tough but some things can

pass through like water and oxygen• Animal cells DO NOT have cell walls

Enter the Cell• Animal cells have cytoskeleton- a protein

“framework” inside the cell that gives the cell its shape

• Cell Membrane- forms a protective barrier between the cytoplasm and the environment outside the cell because an animal cell does not have a cell wall

• ALL cells have cell membranes• Key concept: “The cell membrane controls

what substances come into and out of a cell.”

• To survive a cell must get food, oxygen, and as well as let out waste (like a window screen)

Plant Cells

Animal Cell

Sail on to the Nucleus

• Nucleus is surrounded by the nuclear envelope to protect the nucleus

• Chromatin- thin strands floating in the cell that contains genetic material, instructions for directing the cells functions

• Nucleolus- where ribosomes are made

Nucleus

• Key concept: “The nucleus is the cell’s control center, directing all of the cell’s activities.”

Organelles in the Cytoplasm

• Cytoplasm- a gel-like fluid that many different organelles are found in

• Fluid in the cytoplasm is constantly moving• Key concept: “In the cytoplasm are many

organelles, including mitochondria, endoplasmic reticulum, ribosomes, Golgi bodies, chloroplasts, vacuoles, and lysosomes. Each of these organelles has specific functions in the cell.”

Organelles in the Cytoplasm

• Mitochondria are known as the “powerhouses” of the cell

• They convert energy in food molecules to energy the cell can use to carry out its functions

• Endoplasmic Reticulum is similar to the system of hallways in a building.

• Proteins and other materials move throughout the cell using the endoplasmic reticulum.

• The spots on this organelle are ribosomes, which produce proteins.

Mitochondria

Endoplasmic Reticulum

Organelles in the Cytoplasm• Golgi Body- receive proteins and

other newly formed materials from the endoplasmic reticulum, package, and distribute them to other parts of the cell.

• Called the cells mailroom• Flattened sacs and tubes

• Chloroplasts- capture energy from the sunlight and use it to produce food for the cell

• Only in plant cells (and some other organisms)

• They are green in color giving the plant a green color

Golgi Body

Plant cells

• Vacuole- stores water, food, waste, and other materials

• some animal cells have vacuoles that store food, water, waste, and other materials

• large water filled sacks• most plant cells have one

 

 

 

 

 

 

Organelles in the Cytoplasm

• Ribosomes- small structures that function like factories to produce proteins

• they may float in the cytoplasm or be attached to the endoplasmic reticulum

Organelles in the Cytoplasm

• Lysosomes- small organelles that contain chemicals that breaks down food particles and worn-out cell parts

• small round structures• the “clean-up crew”

Cell Diversity

• Key Concept: “The variety of structure in cells reflects differences in cell function.”

• Some cells have certain organelles but not others• Some cells have more of one type of organelles• Cells come in different shapes

Nerve Cell

Blood Cell

Looking Back

What role do the cell wall and cell membrane play in the cell?What is the role of the nucleus in the cell?What organelles are found in the cytoplasm and what are their functions?How do cells differ?