Transcript SBI 4U biochem 3

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.