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Cell Structure and Functions Chapter 2. Cell Organelles. Nucleus. The largest organelle in animals Contains the organism’s genetic material in the form of DNA Controls cell function by regulating gene expression (protein synthesis) Controls DNA replication during the cell cycle - PowerPoint PPT Presentation
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Cell Structure and Functions
Chapter 2
Cell Organelles
Nucleus The largest organelle in animals Contains the organism’s genetic
material in the form of DNA Controls cell function by regulating
gene expression (protein synthesis) Controls DNA replication during the cell
cycle Located towards the center of the cell
for protection
Nucleus continued… Nuclear envelope (membrane) – surrounds
the nucleus to separate it from the cytoplasm Contains pores to allow RNA and proteins to
enter and leave the nucleus DNA within the nucleus is in the form of
chromatin
Nucleolus Found within the nucleus Function is to create rRNA and form
ribosomes for gene expression Ribosomes pass through the nuclear
pores into the cytoplasm
Ribosomes Consists of rRNA and proteins Used during translation of gene expression
by linking amino acids together to form proteins
Exist all through out the cell
Endoplasmic Reticulum Two types: Rough and Smooth
Rough ER Bumpy appearance due to ribosomes
that cover the outside membrane Synthesizes and packs proteins Transports the proteins that are made
from the ribosomes Forms vesicles around the proteins and
pinches off
Smooth ER Smooth appearance
because it lacks ribosomes
Acts as storage for ions and steroids for when the cell may need them.
Creates steroids and lipids
Breaks down toxic substances.
Vesicle Small, membrane-bound spheres whose
contents are isolated from the surrounding cytoplasm
Transport materials into and out of the cell using endocytosis and exocytosis
Endocytosis Endocytosis: Movement of a substance
into the cell Cell membrane forms a pouch around a
substance, then pinches off from the membrane to form a vesicle with the substance inside.
Vesicle is fused with a lysosome, which breaks down the membrane to release the food
Endocytosis continued…
Three types: Pinocytosis, phagocytosis, and receptor-mediated endocytosis
Pinocytosis: “cell drinking”. Cell is taking in a liquid substance such as extracellular fluid or dissolved particles.
Phagocytosis: “cell eating”. Cell is taking in a solid substance such as bacteria, debris, or other large objects
Pino
cyto
sis
Phagocytosis
Endocytosis: Receptor-mediated
Receptor proteins on the cell membrane recognize specific molecules that the cell needs
After ligand binds to receptor, a message is sent through the membrane to the nucleus
Endocytosis: Receptor-mediated A protein coat
forms when enough receptors are bound
Vesicle forms with the protein coat surrounding it
Vesicle will fuse with a lysosome to release the contents
Exocytosis Movement of a substance by a vesicle to
the outside of a cell. Vesicle fuses with the membrane and
releases contents, such as proteins.
Golgi Complex Vesicles with newly
made proteins are transported from the ER to the Golgi Complex.
A set of flattened, membrane-bound sacs that pack and distribute proteins
Enzymes within Golgi modify proteins and create new vesicles
Lysosomes Vesicles with newly made proteins may stay
in the cell and become lysosomes while some are released outside of the cell via exocytosis
Holds digestive enzymes Breaks down the cell when it dies, damaged
organelles, or foreign materials
Overview…1. Nucleolus creates
ribosomes2. Ribosomes move to rough
ER3. Ribosomes on rough ER
create proteins4. Rough ER transports the
proteins to the Golgi complex using vesicles
5. The vesicles fuse with the Golgi complex
6. The Golgi complex modifies the proteins using enzymes and creates another vesicle
7. The new vesicle travels to the cell membrane to be released or stays within the cell to become a lysosome
Mitochondria Harvests energy from
organic compounds to make ATP
Some cells have much more mitochondria than others, such as muscle cells.
Contains two membranes – smooth outer membrane and a folded inner membrane with large surface area.
Mitochondria continued… Also contains its own DNA and ribosomes Where cellular respiration occurs
Cellular Respiration Process of creating cell energy The cell uses oxygen to break down
glucose (sugar), which creates energy
C6H12O6 + 6O2 ⇒ 6CO2 + 6H2O + energy Sugar + Oxygen ⇒ Carbon Dioxide + water + energy
Chloroplast Only in plant cells Contains chlorophyll – gives the plant a
green color Contains a double outer membrane. Stroma - an area inside of the chloroplast
where reactions occur and sugars are created
Chloroplast Continued…
Carry out photosynthesis by capturing light and creating energy
Energy is in the form of ATP: Adenosine Tri-Phosphate
Uses the sun to convert water and CO2 into oxygen and sugar
6CO2 + 6H2O ⇒ C6H12O6 + 6O2 Carbon Dioxide + Water ⇒ Sugar +
Oxygen
Cell Wall Only found in plant cells NOT the same as the cell
membrane Composed of proteins
and carbohydrates (cellulose)
For support and shape of the cell – Rigid shape
Protects cell from damage – Strong structure
Connects with adjacent cells
Photosynthesis vs. Cellular Respiration
Vacuole Are in both plant and animals cells, but
much larger in plant cells. Stores food, waste, and water In plants, it stores a lot of water and takes
up more than ½ of the cell’s volume. Gives a plant cell support and structure
Animal vs. Plant Vacuoles