Biology Exam III

Which organelle does photosynthesis in plants occur

chloroplast

In which organ does photosynthesis occur

Leaf

Where does the gas exchange occur

Stomata

What is the stroma

surrounds thylakoid and is where the calvin cycle occursas the fluid-filled space within the chloroplast, playing a crucial role in synthesizing sugars during photosynthesis.

What is thylakoids

Membrane-bound structures in chloroplasts that contain chlorophyll and are the site of the light-dependent reactions of photosynthesis. Arranged in stacks of grana

What is the thylakoid space

(lumen) enclosed by thylakoid membrane: accumulates protons h+ during light reactions to create a gradient for atp synthesis

6co2+12h2o+light: c6h12o6+6h2o+6o2 is simplified to what

6co2+6h2o+light: c6h12o6+6o2

What is the light reactions

solar energy absorbed by chlorophyll, energy excites electrons, which are transferred to a carrier (nadp+ nadph) atp is produced in this process

What is the calvin cycle

captured energy used to convert co2 to glucose

Where does the light reactions occur

thylakoid membrane

wht are the inputs for light reactions

h2o, nadp+, adp, pi

what are the outputs for light reactions

o2, atp, nadph

Where does the calvin cycle occur

stroma

What are the inputs of calvin cycle

co2, atp, nadph

What are the outputs of the calvin cycle

g3p, adp, nadp+, Pi

What is wavelength of red light

680nm

what is the wavelength of yellow-green light

550nm

what is the wavelength of violet light

410nm

Shorter wavlength = how much energy

higher

Longer wavelength= how much energy

lower

What are pigments

Molecules thta absorb light: transmitted or reflected

What is the structures of chlorophyll stucture

porphryin ring:light absorbing head of molecule and hydrocrabon tail: interacts with hydrophobic regions of proteins inside thylakoid membranes of chloroplasts

What are photosystems

absorbed energy used to split h2o molecules, electrons liberated form h2o transported in series of redox reactions, leads to production of nadph and atp

What is light harvesting complex

part of photosystem that collects light energy: contains chlorophyll, absorbs sunlight, passes the energy to the reaction center, and the reaction center energizes electrons

Photosytem II

LHC absorbs sunlight, energy goes to the reaction center, electrons get excited by light, water is split to replace the lost electrons, splitting water releases: electrons, h+, and oxygen

Electron Transport Chain

After leaving psII electrons travle through here: electrons moved through the etc proteins, their energy is used to pump h+ ions into thylakoid space, h+ builds up inside the thylakoid, h+ flows through atp synthase, atp synthase makes atp

Photosystem I

LHC absorbs more sunlight, energy excites electrons again, electrons leave psI, electrons travel to nadp+, nadp+ accepts the electrons and h+ to become nadph

Production of NADPH

Nadph is made when nadp+ gains electrons and hydrogen, nadp+ is empty electron carrier. nadph is the electron carrier filled with high energy electrons, nadph carries energy to the calvin cycle

Linear electron flow

Entire process where electrons travel in one direction, sunlight hits psII, water splits releasing oxygen h+ and electrons, electrons travel through the etc, h+ buildup helps atp synthase make atp, electrons reachh psI, sunlight excites the electrons again, electrons help turn nadp+ into nadph

What is cyclic electron flow

electrons from primary electron accpetor in psII feedback into psI, in process more atp generated. Provides more atp necessary for calvin cycle

Chemiosmosis and atp production during photosynthesis photophosphorylation

light hits psII water splits o2, h+, electrons, etc pumps h+ into thylakoid space, psI light re-energizes electrons, nadp+ reductase makes nadph. meanwhile h+ flows through atp synthases and atp is made, atp+nadph go into calvin cycle

What are the products of light reactions

start with h20, end with o2,atp,nadph

o2 diffuses out of chloroplast and out of leaf tissue

atp and nadph remain in stroma and feed into calvin cycle

Calvin cycle

Starts with co2

co2 interacts with ribulose to form 6c rubisco

rubisco converted to 2 molecules of 3 phosphoglycerate

atp from light reactions is hydrolyzed to phosphorylate 3-1,3 biphosphogylcerate

1,3bpg reduced to g3p

some g3p converted to rubp hydrolyzing more atp

How do cells communicate

chemical and electrical signals

direct communication via specialized junctions

gap junctions, plasmodesmata

cell-cell adhesion

attached to each other by membrane bound molecules

paracrine(local) signaling

cell a releases chemical signal which diffuses locally to have an effect on cell b must have appropriate receptors

Hormonal signaling (long-distance)

Cell A releases hormone which is carried long distances to target

cell(s) via circulatory system Target cells must have appropriate receptors

What is a ligan

chemical signal

What is a ligand detected by

cell surface receptor or intracellular receptor

what does binding of a ligand do

alters conformation of receptor, alters its activity or ability to interact with other molecules in target cell

What are g protein coupled receptors

Interact with G proteins intracellularly upon ligand binding G proteins: molecules capable of binding guanine (G) nucleotides (that is, GDP and GTP

G protein coupled receptors

ALL GPCRs have 7 transmembrane domains (-helices) joined by hydrophilic loops that extend into the extracellular or intracellular space

what are ion channel receptors

ligand either opens or closes gate on an ion channel in plasma membrane of target cell, alters flow of ions across membrane

What are signal transduction pathways

Cascades of intracellular molecular interactions triggered by ligand/receptor interaction, Activation usually accomplished by conformational change in proteins of cascaden Allows for amplification of signal One activated receptor might activate multiple molecules of next component in cascade

Conformational change may be brought about by what

phosphorylation

What is phosphorylation

The addition of a phosphate group to another protein, Catalyzed by enzymes referred to as kinases

What are second messengers

Key intracellular players in many signal transduction cascades Involved in many pathways triggered by GPCRs and RTKs (camp, cgmp, ca2+)

What is cyclic amp

Synthesized from ATP by enzyme adenylyl cyclase Broken down to AMP by phosphodiesterase

Ca2+ as second messenger

[Ca2+] maintained low in cytoplasm by action of Ca2+ pumps, Ca2+ pumps use energy from ATP to move Ca2+ from cytoplasm to the outside or from cytoplasm to ER or mitochondria

What is cytoplasmic responses

Activation of an enzyme and Opening of a channel

What is nuclear responses

Activation or inhibition of transcription

What is a genome

complete set of genetic material (dna or rna)

what is a chromosome

Dna wrapped tightly around proteins called histones, 1 chromosome in prokaryotes (23pairs), circular in prokaryotes and linear in eukaryotes

What is chromatin

complex mixture of dna, rna, and proteins found inside nucleus

What is a centromere

duplicated chromosomes joined

What is a sister chromatid

each chromosome of a duplicated pair, sister chromatids will seperate and become daughter cells

what is g1

where the cell grows and does it daily job

what is s phase

the cell makes an exact copy of all its dna

what is g2

the cell grows and finishes making proteins and organizes the copied material getting everything ready

What is centrosome

primary microtubule organizing center

what is mitotic spindle

apparatus along which chromosomes move during mitosis

Prophase

reoginization of mts, chromosmes condense

what is mitotic spindle

each of the 2 centrosomes is a pole mts form spinlde and aster

prometaphase

kinectochore mts attach to kinectochores of sister chromatids, chromosomes condense, nuclear envelope breaks down

What is a kinectochore

protein structure that assembles at centromere of each sister chromatid

metaphase

mitotic spindle complete, chromosomes aling and plate, aster mts radiate toward pm and form attachments

anaphase

separation of sister chromatids, moto proteins walk along kinetochore mts toward spindle poles, as it walks mt disassemble, non kinetochore mts lengthen pushing poles further apart causing cell to lengthen

telophase

nuclei reform, chromosomes become less condensed, occurs simultaneously with cytokinesis formation of cleavage furrow which divides cell in two.

binary fission

1 circular chromosome is duplicated called origin of replication, after duplication moves to opposite pole of cell, plasma membrane pinches inward new cell wall is deposited, two daughter cells result

what causes cell cycle to progress

Several checkpoints, where cell must receive a “go-ahead” signal for cell cycle progression, present in cytoplasm

what is the nature of the go ahead signals

cyclin dependent kinases

cdks and m phase promoting factor

A Cdk that triggers entry into M phase When bound to cyclin, Cdk phosphorylates proteins of nuclear lamina

what causes fluctuations in cyclins

signals from environment, exposure to growth factors, density dependent growth inhibition, and anchorage dependent growth

Exposure to growth factors

PDGF = platelet derived growth factor PDGF stimulates fibroblasts to divide

mutations affecting cell cycle control

random spontaneous mutations, mutations in dna resulting from xrays, uv exposure, chemical carcinogens, viruses

what are proto oncogenes

Normally encode proteins involved in growth and

development

 Growth factors

 Growth factor receptors

 Intracellular signaling molecules (like Cdks)

 When mutated to oncogenes → cancer

tumor suppressor genes

Normally encode proteins that inhibit cell division

 Mutation results in a lack of inhibition → unchecked cell division →cancer

what is ras gene

Mutation in ras gene → production of hyperactive Ras protein → too much cell division

what is p53 gener a tumor suppressor gener

Normal p53 protein blocks cell division; mutated form can not

what is genetic predisposition

Inheritance of a mutated gene increases chances that an individual will accumulate “enough” mutations for cancer to occur

how many daughter cells does mitotic division produce

2 daughter cells

what is asexual reproduction

 1 parent

 Offspring are genetically identical

to parent

 Budding, Fragmentatio

what is sexual reproduction

 2 parents

 Offspring contain combination of

genes from both parents

 Offspring is genetically identical

to neither parent, but similar to

both

what is somatic cells

vast majority of cells in human body

 Contain 46 chromosomes

 23 pairs of homologous chromosomes! (1 chromosome of

each pair came from mom, the other from dad)

 Diploid:

what is gametes

Reproductive cells (sperm and egg)

 Contain 23 chromosomes

haploid

what is karyotype

Ordered display of all 46 chromosomes from a human somatic cell arrested in

metaphase

what is homologous chromosomes with karyotyping

same length, have same centromeric position, and stain similarly with certain dyes

meiosis I

Meiosis I separates homologous chromosomes

Meiosis II

seperates sister chromatids

events unique to prophase 1

tetrad formation (aka Synapsis)

 Homologous chromosomes align along

their lengths and form complexes with

each other (called tetrads)

 Protein complex that hold homologous

chromosomes together in a tetrad called

the synaptonemal complex

crossing over

what is crossing over prophase I

Exchange of chromosome pieces between non-sister chromatids of aligned homologous chromosomes sites where crossing over occurs called chiasmata, produces recombinant chromosomes

events unique to metaphase I

Tetrads line up on metaphase I plate

 Alignment is random

 i.e., some maternal chromosomes will end up on one side, some on the other

 Independent assortment of chromosomes

 Increases genetic variation!*Think of it as re-shuffling the

deck!

What is independent assortment

Alignment is random with respect to which side the maternal and paternal chromosomes end up on

what is human spermatogenesis

Occurs in seminiferous tubules of testes (male gonads)

Mature sperm: Form fits function

head: carries dna

acrosome: helps dna enter egg

midpeice: provides energy

long tail: helps it swim

plasma membrane protects the cell

Human oogenesis

Occurs in ovaries (female gonads) Begins in human female embryo (around 2nd month of gestation

Fertillization

 Joining of haploid sperm and egg

 Forms diploid zygote (single-celled embryo)

Cleavage

 Period of rapid mitotic cell division

 Ends with a multicellular blastula

Gastrulation

Massive rearrangement of cells to form 3-layered structure

(called a gastrula)

 Ectoderm: nervous system epidermis of skin

 Mesoderm: skeletal and muscular system

 Endoderm: lining of digestive tract