Structures and Functions of

Eukaryotic Cells

Animal Cell

Plant Cell

Nucleus• Contains DNA, which stores and copies

genetic info• DNA forms chromosomes• Structures in the nucleus:

– Nucleolus (contains RNA and proteins)– Nuclear envelope (has pores in its double

phospholipd bilayer that allow some particles to pass through)

Endoplasmic Reticulum• Membranous bound tubules• Rough ER has ribosomes attached that make

proteins• Smooth ER makes lipids and phospholipids,

detoxifies drugs/alcohol, makes hormones.

Golgi Apparatus• Stack of curved membrane sacs• Works with nuclear envelope, ER and vesicles as a

part of a protein and lipid modification and transport system.

• Initial proteins/lipids are made by the ER and sent in a vesicle to the Golgi

• Proteins/lipids are stored or further modified• Proteins/lipids are pinched off to form vesicles that will

exit the cell or go to another spot in that cell.• In animal cells the Golgi also produces lysosomes

Lysosomes

• membrane bound sacs that have digestive enzymes in them

• Catalyze hydrolysis reactions

• Breaks down macromolecules

• Acidic inside (pH of 5)

Peroxisomes

• Membrane-bound sacs containing enzymes

• Form from budding off the ER

• Catalyze redox reactions

• Breaks down some toxic molecules, such as alcohol.

Vesicles and Vacuoles

• Vesicle: term used to describe membrane-bound sacs used for transportation throughout the cell

• Vacuole: central large vesicle found in plant cells that contains water, enzymes, ions, sugars, amino acids.

• The vacuole helps give the plant shape through turgor pressure

Chloroplasts

• Found in plant cells• Contain chlorophyll that absorbs sunlight

energy during photosynthesis• Has a thick liquid called the stroma inside• Inner membrane surrounds many flattened

disks called thylakoids• Many thylakoids are stacked on top of

each other to form a granum (pl. grana)• Contain their own DNA

Mitochondria

• Break down molecules for energy

• 2 membranes

• Inner membrane is folded and called the cristae

• Space inside the inner membrane is called the matrix.

• Contain their own DNA

Cell Wall

• Plants, fungi and some protists have a cell wall

• Provides structure and support

• Plant cell walls are comprised of cellulose

• Fungi cell walls are made of chitin

Cytoskeleton

• Internal network of fibres throughout the cytoplasm

• Provide structure and anchoring for cell membrane and organelles

• Types: – Microtubules: thickest, shape, help with cell division,

movement of organelles– Intermediate filaments: shape, anchor organelles and

scaffolding of nucleus– Microfilaments: thinnest, shape, muscle contractions,

cell division

Cilia and Flagella

• Flagella are longer, maybe only one or two

• Cilia are shorter and there are many

• Help with movement of cell

Cell Membrane

• Regulates the passage of molecules and ions into and out of the cell.

• The model we use is called the fluid mosaic model which contains the phospholipid bilayer, integral proteins, cholesterol and carbohydrate groups attached to lipids or proteins (glycolipids, glycoproteins)

• Because the phospholipids are held together through weaker intermolecular bonds, they can move around freely.

Fluidity of a Membrane• Should maintain its fluidity because if too fluid, it

lets too many molecules into the cell.• Temperature, presence of double bonds in the

fatty acid tails (more double bonds = not as tightly packed) and length of fatty acid tails (longer chain = more intermolecular interactions) can contribute to fluidity.

• Presence of cholesterol decreases fluidity at room temperature by increasing intermolecular forces. Cholesterol can increase fluidity at lower temperatures by breaking up the tight packing of the phospholipids.

Membrane Proteins• Integral proteins are embedded in the membrane.• Peripheral proteins are more loosely attached to the

inside of the membrane.• They help to stabilize the cell and give it shape by

connecting to the cytoskeleton• Transport: move substances across the membrane• Catalyst: work as enzymes• Cell recognition: carb chains enable cells to

recognize each other• Signal reception and transduction: receptor proteins

bind to signal molecules such as hormones and can send signals elsewhere.

Practice: Page 42 # 1, 5, 8, 9.