BIO 181 Exam 2 Review

What are the 3 main arguments of the cell theory?

• One or more cells comprise all living things

• The cell is the basic unit of life

  • New cells arise from existing cells

What are the four common components of the cell?

Cytoplasm, DNA, Ribosomes, and Plasma membranes

What is the cytoplasm?

Fills the inside of the cell; contains jelly-like cytosol

What is DNA?

genetic material

What are ribosomes?

synthesizes proteins

• (“Read” instructions (RNA) and make amino acid chains that form proteins

• Location: nuclear envelope, endoplasmic reticulum, free-floating

What is the plasma membrane?

separate cell contents from the environment & control entry/exit of things

• Made up of a phospholipid bilayer and embedded proteins

• Main feature of ALL cells

What are the cell types?

Prokaryotic and Eukaryotic

What are prokaryotic cells?

simpler, single-celled

What are eukaryotic cells?

generally more complex animal and plant cells

What are the features of prokaryotic cells?

• No nucleus (has nucleoid with circular DNA)

• Much smaller than eukaryotic cells

• Benefits:

  • Ions & other molecules enter easily

  • Waste can be easily excreted

What are the features of eukaryotic cells?

1. Membrane-bound nucleus

2. Multiple rod-shaped chromosomes

3. Multiple membrane-bound organelles

Membrane-bound nucleus of eukaryotic cells

• Nucleus: contains DNA; direct synthesis of proteins

• Nuclear Envelope: double membrane surrounding the nucleus

Rod-shaped chromosomes of eukaryotic cells

• Have Histones: a protein associated with DNA

Membrane-bound organelles in eukaryotic cells

• Mitochondria: “powerhouse of the cell”

  • Function: generates energy (ATP)

  • Cellular respiration: glucose, oxygen —> ATP & CO2

  • Has own DNA & Ribosomes

• Peroxisomes

  • Function: perform chemical reactions that break down waste products and helps detox

What are the structures in animal cells?

Centrosomes, Lysosomes, Endoplasmic Reticulum (ER), Golgi Apparatus

What are the centrosomes?

• Where microtubules connect

• Function: not completely known; has a role in cell division

• Main microtubule organizing center (MTOC) in animal cells near the nucleus

What are lysosomes?

• Garbage disposal

• Function: break down waste products (via enzymes inside)

• Spherical sacs in animal cells

What is the endoplasmic reticulum?

• Rough ER:

  • Contains many ribosomes; location for protein synthesis

• Smooth ER:

  • Doesn’t contain ribosomes; lipid synthesis

• Network of sacs and tubes that help synthesize, fold, and transport proteins and lipids in animal cells

What is the golgi apparatus?

• Modifies (packages) proteins

  • Flattened, stacked pouches (usually 4-8) in animal cells

What is the cell wall?

• Function: protection and structural support

• Made of cellulose (sugar)

• Found in plant cells

What are chloroplasts?

• Function: photosynthesis

• Green pigment

• Has own DNA & Ribosomes

What is the endosymbiont theory?

Repeated endosymbiosis events in bacteria eventually lead to modern eukaryotes

• Bacteria (prokaryotes) engulfed one another, forming mitochondria and chloroplasts

What are the structure of the membrane?

Lipids, Proteins, Carbohydrates

What are peripheral proteins?

• On the membrane interior or exterior of the membrane

• Attached to integrins or phospholipids

• Function: structure, recognition sites, etc.

Carbohydrates on the cell membrane

• Always on the exterior

• Bound to proteins or lipids

  • Function: identification via their patterns

What is selective permeability?

• Allows passage of some things but not others

• Major feature of the cell membrane

  • Different internal vs. external environment

Easy passage across the membrane

• Nonpolar

• Lipid-soluble (hydrophobic)

• Low molecular weight

Difficult passage across the membrane

• Polar

• Hydrophilic

• High molecular weight (large molecules)

• Charged ion

Passive transport?

Doesn’t require energy (ATP) and moves WITH the gradient

Active Transport

Requires energy moving AGAINST the gradient

What is diffusion?

The movement of particles from an area of high concentration to an area of low concentration to balance the sides of a membrane

• No energy input; Passive transport

Concentration Gradient

Helps describe the direction things move based on differences in concentration; flows from crowded areas to less crowded areas

Osmosis

Movement of water with water’s gradient

• The water crosses to reach equilibrium

• Moves from high water potential (low solute) to low water potential (high solute)

• Passive transport

What is tonicity?

The ability of a solution to cause osmosis; describes solute concentrations

What are the three types of tonicity?

Hypertonic, isotonic, hypotonic

What is hypertonic solution?

when the solute concentration outside the cell is higher than inside the cell

What is isotonic solution?

when the solute concentration outside the cell is equal to the concentration inside

What is hypotonic solution?

when the solute concentration outside the cell is lower than inside the cell

What is facilitated diffusion?

Helps the movement of ions or molecules across the membrane using transporter proteins

• Passive transport

What are channel proteins?

Forms a channel through the membrane, allowing specific molecules or ions to pass through passively (doesn’t bind to solute)

• type of transporter protein

What are carrier proteins?

Binds to specific solutes, undergo a conformation change, and transport the solute across the membrane

• type of transporter protein

What proteins are used for active transport?

Carrier proteins (pumps)

Primary Active Transport

• Requires energy (ATP)

• Uses protein transporters

• Moves solute against gradient (low to high)

Secondary Active Transport

• Requires energy, but NOT ATP (uses stored energy)

• Uses protein transporters

• Moves things using the electrochemical gradient built by primary active transport

What are the phases of the cell cycle?

Interphase and Mitotic phase

Interphase Steps

G1, Synthesis, G2

What is G1 phase of the interphase?

• Accumulating things to be used for S phase

• DNA Building Blocks: Nucleotides & Proteins

• Energy reserves

What is synthesis phase of interphase?

• DNA is replicated

• Centrosome is duplicated

• Mitotic spindle forms

What is G2 phase of interphase?

• More cell growth and preparation for mitosis

• Replenish energy

• Synthesize more proteins

• Duplication of some organelles

The mitotic phase

• Includes mitosis & cytokinesis

• Product: two identical daughter cells

Prophase

• 1st phase of mitotic

• Nuclear envelope breaks down

• Centrosomes start moving to opposite poles

• Sister chromatids condense

• Microtubules begin to extend

Prometaphase

• 2nd phase of mitotic

• Steps of prophase continue further

• Chromatids form kinetochores (proteins that attract microtubules)

• Microtubules attach to kinetochores on chromatids

Metaphase

• 3rd phase of mitotic

• Chromosomes align on metaphase plate

• Sister chromatids are still tightly attached to each other

Anaphase

• 4th phase of mitotic

• Sister chromatids separate at the centromere

• Each chromatid (chromosome) is pulled by microtubule to opposite sides

• Cell is visibly elongated

Telophase

• 5th phase of mitotic

• Nuclear envelope reforms

• Chromosomes decondense to chromatin

Cytokinesis

• 6th and final phase of mitotic

• Makes two identical daughter cells; one turns into two

What is the G0 phase?

when no active division is occurring

• cells aren’t going through interphase/mitosis

• some nerve cells rarely or never divide

Cancer

Uncontrolled cell growth and division

• proteins that play a role in cell division are affected by DNA mutations

What are the cell cycle checkpoints?

G1, G2, M

G1 Checkpoint

• Correct cell size

• Adequate reserves

• No DNA damage

G2 Checkpoint

• Correct chromosome duplication

• No DNA damage

M Checkpoint

• Microtubules are attached to the chromatids

What are proto-oncogenes

healthy genes that, when mutated, become oncogenes and result in cancer (+ regulators)

• responsible for regulating cell growth, division, and survival

• acts like an accelerator pedal in a car, telling cells when to grow and divide; accelerator not stuck

What are oncogenes?

mutated genes that can cause cancer; accelerator is stuck

• uncontrollable division of cells, forming tumors

What are unmutated tumor suppressor genes?

prevents uncontrolled growth (cancer) by slowing down/stopping the cell cycle (negative regulators); brakes can be pressed

What are mutated tumor suppressor genes?

when protein can’t slow the cell cycle; brakes can’t be pressed

What is cell signaling?

communication that governs basic cell activities and coordinates cell actions

• Important for single-cell prokaryotes and multicellular organisms

Ligands

interacts with proteins in target cells, cells affected by chemical signals

Receptors

protein molecules in the target cell or on its surface that bind ligands

What are the signaling types?

autocrine, signaling across gap junctions, paracrine, and endocrine

Autocrine Signaling

A cell targets itself; the ligand produced by the cell signals to the same cell

Gap Junction Signaling

a cell targets another cell connected by gap junction

(Plasmodesmata in plants)

Gap Junctions

channels that allow ligands to flow through

Paracrine Signaling

a cell targets nearby cells

(Ex: Neuron signaling)

Endocrine Signaling

a cell sends signals through the bloodstream to other cells/distant cells

What are the two receptor types?

Internal Receptors and Cell-Surface Receptors

Internal receptors (intracellular/cytoplasmic receptors)

• many bind directly to DNA to influence gene expression

• Ligands are usually hydrophobic because they can cross the membrane

Cell-Surface receptors (transmembrane receptors)

Ion Channel-Linked, G-Protein-Linked, Enzyme-Linked types

Ion Channel-Linked receptors

Ligand binding causes the ion channel to open/close

G-Protein-Linked receptors (multiple component receptor)

multiple component receptor:

1. Ligand binds receptors

- alpha subunits binds GTP where GDP was (GDP→GTP)

2. Alpha subunit separates from the beta/gamma subunits

- response ensues when beta and alpha interact with other things

3. The alpha subunit converts GTP to GDP (GTP→GDP)

- G-protein reattaches to receptor

Enzyme-Linked receptors (kinase receptors)

usually work in pairs

Ligand types

• Small hydrophobic

  • To be soluble in blood, transported by carrier proteins

• Hydrophilic

  • polar, water soluble

  • large & can’t cross membrane

  • bind to extracellular receptors

  • peptides and proteins

• Other

  • small nonpolar

  • short-half life, travel short distances