AP Biology- Unit 2: Cell Structure and Function

Cells

Small things that make up living things

Two Kinds of Cells

• Eukaryotic

• Prokaryotic

Prokaryotic Cells

Single-celled organisms that lack a membrane-bound nucleus and organelles; they are simpler than eukaryotic cells, and their DNA is found in a region called the nucleoid, found in bacteria and archaea

Eukaryotic Cells

Complex cells that have a nucleus and organelles; they can be single-celled or multicellular organisms, and their DNA is organized into chromosomes within the nucleus, found in plants and animals

Basic Features of All Cells

• Plasma membrane

• Semifluid substance (cytosol)

• Chromosomes

• Ribosomes

Organelles

Smaller structures in eukaryotic cells

Nucleus

• Largest organelle in the cell

• Directs what goes on in the cell

• Responsible for cell’s ability to reproduce

• Home of DNA (chromosomes)

• Nucleolus in nucleus

  • RNA is made and ribosomes are assembled

Ribosomes

• Organelle that is the site of protein synthesis

• Job is to manufacture all proteins required by the cell or secreted by the cell

• Has larger and smaller subunit

• Structure composed of rRNA and proteins

• Can float freely or be attached to E.R.

Rough Endoplasmic Reticulum (rough E.R.)

• Organelle studded with ribosomes which secrete glycoproteins

• Distributes transport vesicles, proteins, surrounded by membranes

• Membrane factory for the cell

• Sends off proteins across membrane or used to build Golgi bodies, lysosomes, or the E.R.

Smooth Endoplasmic Reticulum (Smooth E.R.)

• Organelle that makes lipids, hormones, steroids, and breaks down toxic chemicals

• Metabolizes carbohydrates

• Stores calcium ions

Golgi Bodies

• Organelle that modifies processes and sorts the proteins

• Packages final products in vesicles which carry products to the plasma membrane

• Production of lysosomes

Mitochondria

• POWERHOUSE OF THE CELL!!

• Produces ATP (energy for cell)

• Has inner folds called (cristae)

  • Most of the production of ATP is done on the cristae

Lysosomes

• Organelle that carries digestive enzymes which are used to break down, old worn out organelles, debris or large ingested particles

• Contains hydrolytic enzymes that function only at acidic pH

• Can hydrolyze proteins, fats, polysaccharides, and nucleic acids

Centrioles

• Organelle that produces micro tubules during cell division which pull chromosomes apart and move them

• Not found in plant cells

Vacuoles

• Organelles filled with water, good, waste, salts, or pigments

Cytoskeleton

• Organelle that holds together the cell with fibers called micro tubules and micro filaments

• Assists in cell movement

Cilia and Flagella

• Organelle that helps move around organisms in watery environments

• Some help get rid of dust and debris around

Peroxisomes

• Organelles that detoxify various substances, producing hydrogen peroxide (H2O2) as a byproduct of

• Contain enzymes that breakdown hydrogen peroxide into oxygen and water

• Common in liver and kidney cells

Plant Cells vs. Animal Cells

• Plant cells have a cell wall, animal cells do not

• Plant cells have chloroplasts, animal cells do not

• Plant cells have a central vacuole, animal cells do not

Endosymbiosis Hypothesis

• Theory that chloroplasts and mitochondria could have been separate from cells, but combined due to evolution

  • Both organelles have their own DNA, reproduce through binary fission, have their own ribosomes, and are all similar to prokaryotic cells

Plasma Membrane (Phospholipid Bilayer)

• Double layered structure made up of mostly phospholipids and proteins

  • Hydrophilic phosphate heads face outwards

  • Hydrophobic fatty acid tails face inwards

• Important because it regulates the movement of substances into and out of the cell

• The membrane itself is semipermeable

• Only certain substances, namely small hydrophobic molecules pass through it unaided

Peripheral Proteins

Proteins loosely associated with the lipid bilayer, located on the inner or outer surface of the membrane

Integral Proteins

Proteins firmly bound to the plasma membrane

• Amphipathic, meaning their parts can extend into different regions of membrane

• Those who extend all the way through the membrane are called transmembrane proteins

Adhesion Proteins

Proteins that form junctions between adjacent cells

Receptor Proteins

Proteins that serve as docking sites for arrivals at the cell

Transport Proteins

Proteins that form pumps that use ATP to actively transport solutes across the membrane

Channel Protein

Protein that forms channels that selectively allow the passage of certain ions and molecules

Cell Surface Markers

Proteins that play a role in cell recognition and adhesion

Simple Diffusion

Transport where something with a high concentration spreads out and diffuses to an area with lower concentration (passive transport because energy is not needed)

Facilitated Diffusion

Transport where a channel-type protein is needed

Aquaporins

Water specific channels in membrane

Osmosis

Transport that is diffusing with water

Tonicity

Term to describe the gradients of osmosis

Isotonic Solution

Solution where the solute concentration is the same both inside and out

• Conditions just right for the cell

Hypotonic Solution

Solution where there is less dissolved solutes than the cell

• Will cause cell to burst

Hypertonic Solution

Solution where there are more dissolved solutes than in the cell

• Will cause the cell to shrivel up/shrink

Water Potential

The measure of potential energy in water and describes the eagerness of water to flow from an area of high water potential to an area of low water potential

Active Transport

Transport where low concentration moves to high concentration (requires energy); ex: Sodium-potassium pump

Endocytosis

• Membrane method of engulfing particle

  • pinches and forms a vesicle

Pinocytosis

Type of endocytosis where the cell ingests liquid

Phagocytosis

Type of endocytosis where cell takes in solids

Receptor-Mediated Endocystosis

Type of endocytosis where cell surface receptors work as endocytic pits lined with a protein called clathrin

Bulk Flow

The one-way movement of fluids brought about by pressure; ex: xylem in blood and phloem in plants

Dialysis

The diffusion of solutes across a selectively permeable membrane

Exocytosis

Transport where large particles are ejected out of the cell and expelled into the extra-cellular space