BIOL 1406 Lecture Exam 3

Photosynthesis

conversion process that transforms the energy of sunlight into chemical energy stored in sugars and other organic molecules

Autotrophs

“self-feeders”; sustain themselves without eating anything derived from other living beings

Photoautotrophs

organisms that make their own food using light energy

Chloroplast

eukaryotic organelle that absorbs energy from sunlight to drive the synthesis of organic compounds from CO2 and H2O

where photosynthesis occurs

Thylakoid

a membrane-bound compartment inside chloroplasts where the light-dependent reactions of photosynthesis occur

Stroma

The fluid-filled space inside a chloroplast that surrounds the grana (stacks of thylakoids)

Chlorophyll a

the key light-capturing pigment that participates directly in the light reactions

Chlorophyll

the green pigment that gives leaves their color, resides in the thylakoid membranes of the chloroplast

Chloroplast accessory pigments

Chlorophyll b

Carotenoids

+many more

Chlorophyll b function

assists chlorophyll a by absorbing similar wavelengths 

Carotenoids function

absorbs wavelengths that may be harmful to the plant (UV)

Absorption spectrum

a graph plotting a pigment’s light absorption versus wavelength

Light energy

excites elections in a pigment molecule

excited electrons have more chemical energy

Photosynthesis equation

6CO₂ + 12H₂O —> C₆H₁₂O₆ + 6O₂ + 6H₂O

Light reactions

convert light energy to the chemical energy of ATP and NADPH

occurs in chloroplast thylakoids

split H2O and release O2

Calvin cycle

uses ATP and NADPH to convert CO2 to G3P

occurs in chloroplast stroma

returns ADP, inorganic phosphate, and NADP+ to the light reactions

Light reaction formula

H2O —>—>—> O2

Light reaction products

• O2

• NADPH

• ATP

Photosystems

composed of reaction center complex surrounded by light harvesting complexes

absorb light to excite electrons

Light-harvesting complex

accessory pigments within it transfer energy to chlorophyll a in reaction center

Reaction center complex

contains a pair of chlorophyll a molecules that transfer excited electrons to primary electron acceptor pigment

Photosystem I, II

What are the two types of photosystems that cooperate in the light reactions?

Linear electron flow

the process in photosynthesis where electrons move in a linear path from water through photosystem II and photosystem I before being used to create NADPH

Linear electron flow steps

1. Photon hits PSII, excites electrons in chlorophyll a

2. Primary electron acceptor collects excited electrons, sends to ETC 1

3. ETC 1 used excited electrons to make ATP, sends reduced electron to PSI

4.  Photon re-excites electrons in chlorophyll a, sends to primary electron acceptor

5. Electrons sent to ETC 2, reducing NADP+ to NADPH

ETC #1 function

powers ATP synthesis

• H+ active transport: stroma —> thylakoid space

• chemiosmosis

ETC #2 function

reduces NADP+ to NADPH

Calvin cycle formula

CO2 —>—>—> Glyceraldehyde 3-phosphate

Carbon fixation phase

Calvin cycle phase 1

Rubisco enzyme catalyzes fixation of CO2 (3 per cycle)

6 carbon intermediate splits, forms 2 molecules of 3-phosphoglycerate

Reduction phase

Calvin cycle phase 2

uses ATP and NADPH from light reactions to make 6 glyceraldehyde 3-phosphate

• net 1 G3P produced

Glycolysis or to build larger carbs (glucose, sucrose)

What can the G3P that leaves the Calvin cycle be used for?

Regeneration phase

Calvin cycle phase 3

Uses ATP from light reactions to convert 5 G3P to make 3 ribulose bisphosphate to restart Calvin cycle

Calvin cycle products

• glyceraldehyde 3-phosphate

• ribulose bisphosphate (to repeat)

• ADP

• NADP+

Plasmodesmata

microscopic channels in plant cell walls that connect the cytoplasm of adjacent cells, allowing for the movement of water, ions, and molecules

Tight junctions

this junction establishes a barrier that prevents leakage of extracellular fluid across a layer of epithelial cells

the plasma membranes of neighboring cells are very tightly pressed against each other, bound by specific proteins

Desmosomes

fasten cell membranes together into strong sheets

a type of anchoring junction

Gap junctions

provide cytoplasmic channels from one cell to an adjacent cell, allowing cells to communicate

also called communicating junctions

Paracrine signaling

a signaling cell acts on nearby target cells by secreting molecules of a local regulator (ex: growth factor)

Synaptic signaling

a nerve cell releases neurotransmitter molecules into a synapse, stimulating the target cell (muscle or nerve cell)

Endocrine signaling

specialized endocrine cells secrete hormones into body fluids, affecting only some cells

Cell signaling order

Reception—>Transduction—>Response

Signal Reception

ligands (signaling molecules) bind to receptors that are present on/in target cell, causing it to change shape

Receptor

a protein molecule that binds to specific ligands, leading to signal transduction within the cell

can be intracellular (mobile) or cell-surface transmembrane (immobile)

Signal Transduction

series of molecular events that relay signals from the cells exterior to its interior, ultimately leading to a specific cellular response

Ions, proteins, cAMP

What can relay signals in a signal transduction pathway?

Signal Response

can occur anywhere within target cell and involve any of the target cell’s functions

Protein kinase

an enzyme that transfer phosphate groups from ATP to a protein

Improper cell signaling

The following are consequences of what?

• birth defects

• diabetes

• cancer

Reproduction

Why is cell division important in unicellular organisms?

Reproduction, growth and development, and tissue renewal

Why is cell division important in multicellular organisms?

Binary fission

prokaryotic cell division

results in 2 daughter cells that are identical to each other and parent cell

Chromatin

the entire complex of DNA and proteins that is the building material of chromosomes

made of histone proteins, wound into histone spools

Chromosomes

structure of packaged DNA wound around protein spools

Sister chromatids

joined copies of the original chromosome

Centromere

region where the chromatid is attached most closely to its sister chromatid

Mitosis

daughter cells are identical to parental cell

Meiosis

daughter cells are different from parental cell

Cell cycle

the life of a cell from the time it is first formed during division of a parent cell until its own division into two daughter cells

Interphase

accounts for 90% of cell cycle

G₁, S, G₂ phases

G1 phase

the cell grows and synthesizes proteins and organelles

S phase

DNA replication occurs, resulting in two copies of each chromosome

G2 phase

the cell continues to grow and prepares for mitosis/meiosis

Cell cycle control system

a cyclically operating set of molecules in the cell that both triggers and coordinates key events in the cell cycle

Cyclin

a protein that gets its name from its cyclically fluctuating concentration in the cell

powers cyclin-dependent kinases that power cell cycle

Mitosis phases

1. Prophase

2. Prometaphase

3. Metaphase

4. Anaphase

5. Telophase

6. Cytokinesis

Spindle

controls chromosome movement and separation during cell division

Kinetochore microtubules

physically attach to chromosomes to move them around, then separate them from each other

Centrosome

regions for microtubules to organize and grow out from

Aster

short microtubles that anchor centrosome

Overlapping nonkinetochore microtubules

stretch the cell out in cell division

Kinetochore

protein complex that assembles at chromosome centromere

Benign tumor

most easily extracted tumor

not considered cancerous

Malignant tumor

tumor able to spread to other tissues

Metastatic tumor

tumor able to spread to foreign regions through the blood

Homologous chromosome similarities

• DNA size

• centromere location

• staining pattern

Homologous chromosome differences

• from different parents

• DNA info differences

Meiosis I

Homologous chromosomes separate into 2 total haploid cells with duplicated chromosomes

Meiosis II

Sister chromatids separate into 4 total haploid cells with unduplicated chromosomes

Diploid cell

any cell with 2 chromosome sets

2n

ex: somatic cells

Haploid cell

cells containing a single set of chromosomes

n

ex: gametes

Chiasmata

physical locations where crossing over occurs

Meiosis Prophase I

equal DNA exchange between homologous chromosomes

Recombination phase

Meiosis Metaphase and Anaphase I

Independent assortment of chromosomes

Fertilization

joins gametes from two different parents

Genes

select DNA sequences that tell cell how to make RNA

Character

heritable feature of an organism (ex: flower color)

Trait

version of a character (ex: purple or white flower color)

Allele

different versions of the same gene

Law of Segregation

gene alleles are separated during meiosis to produce haploid gametes

Organism genotypes

_____________ have two copies of every gene (2n)

Gamete genotypes

______________ have one copy of every gene (n)

Law of Independent Assortment

each pair of alleles segregates independently of any other pair of alleles during gamete formation