Exam 2 Study Guide: Cellular Respiration, Photosynthesis & Cell Cycle

96 question-and-answer flashcards covering cellular respiration, photosynthesis, and cell cycle concepts for Exam 2 preparation.

What is the overall summary equation for cellular respiration?

C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + ATP energy

During cellular respiration, what molecule is the initial source of energy and electrons?

Glucose

What is the final electron acceptor in cellular respiration?

Molecular oxygen (O2), which becomes H2O

What molecule is the final energy receiver in cellular respiration?

ADP, which is phosphorylated to ATP

Where in the cell does glycolysis occur?

The cytosol (cytoplasm)

What key molecule enters glycolysis?

Glucose (plus 2 ATP and 2 NAD+)

What are the main products of glycolysis?

2 pyruvate, 2 NADH, net 2 ATP

Where does pyruvate oxidation (link reaction) take place?

Mitochondrial matrix

What enters pyruvate oxidation?

2 pyruvate, NAD+, CoA

What are the products of pyruvate oxidation?

2 acetyl-CoA, 2 NADH, 2 CO2

Where does the Krebs (citric acid) cycle occur?

Mitochondrial matrix

What molecule enters the Krebs cycle?

Acetyl-CoA (along with NAD+, FAD, ADP)

List the chief products of the Krebs cycle per glucose.

6 NADH, 2 FADH2, 2 ATP, 4 CO2

Where is the electron transport chain (ETC) located in eukaryotes?

Inner mitochondrial membrane

What enters the ETC?

NADH, FADH2, O2, ADP + Pi

What are the main products of the ETC and oxidative phosphorylation?

≈28 ATP, H2O, regenerated NAD+ and FAD

Define oxidation in biochemistry.

Loss of electrons (often gain of O or loss of H)

Define reduction in biochemistry.

Gain of electrons (often gain of H)

Which coenzyme shuttles electrons from metabolic pathways to the ETC?

NAD+/NADH

What is the oxidized form of NAD?

NAD+

What is the reduced form of FAD?

FADH2

Describe the structure of ATP.

Adenine base + ribose sugar + three phosphate groups

What is the primary function of ATP?

Universal energy currency—hydrolysis releases usable energy

What is the role of the electron transport chain during respiration?

Transfers electrons to O2 while pumping protons to create a gradient

Which enzyme uses the proton gradient to make ATP?

ATP synthase

What is oxidative phosphorylation?

ATP production driven by the redox-powered proton gradient and chemiosmosis

What is substrate-level phosphorylation?

Direct enzymatic transfer of a phosphate to ADP to form ATP (in glycolysis & Krebs)

How are glycolysis, the link reaction, and the Krebs cycle connected to the ETC?

They supply NADH and FADH2 that feed electrons into the ETC

How is breathing related to cellular respiration?

Inhaled O2 is the final electron acceptor; exhaled CO2 is produced by the Krebs cycle and link step

What happens to the mass of food/fat oxidized in respiration?

Most mass leaves as CO2 and H2O; some energy captured in ATP, the rest lost as heat

Why does cellular respiration keep you alive?

It provides ATP for all energy-requiring cellular processes

What process supplies ATP when muscle cells lack oxygen?

Lactic acid fermentation

During lactic acid fermentation, what is pyruvate reduced to?

Lactate (lactic acid)

How does feedback inhibition slow cellular respiration?

High ATP or citrate inhibits phosphofructokinase, slowing glycolysis

If NADH is converted to NAD+, what happens to its electrons?

They are passed to another molecule; NADH is oxidized

What is the summary equation for photosynthesis?

6 CO2 + 6 H2O + light → C6H12O6 + 6 O2

What are the two major phases of photosynthesis?

Light reactions and the Calvin cycle (dark reactions)

Where do the light reactions occur?

Thylakoid membranes of the chloroplast

Where does the Calvin cycle occur?

Chloroplast stroma

What is the main purpose of the light reactions?

Convert light energy to ATP and NADPH, releasing O2

What is the main purpose of the Calvin cycle?

Fix CO2 into carbohydrates using ATP and NADPH

Which molecules connect the light reactions to the Calvin cycle?

ATP and NADPH

How is NADP+/NADPH similar to NAD+/NADH?

Both are electron carriers; NADPH is used mainly in anabolic pathways like photosynthesis

During photosynthesis, what excites electrons initially?

Energy from sunlight (photons)

What molecule donates electrons to Photosystem II?

Water (H2O)

What is the final electron acceptor of the light reactions?

NADP+, forming NADPH

How is ATP generated in photophosphorylation?

Protons flow through ATP synthase down the thylakoid gradient

How do photosynthesis and respiration complement one another?

Photosynthesis stores energy and releases O2; respiration releases energy and produces CO2

What role do chlorophyll and accessory pigments play?

Absorb light at various wavelengths to drive photosynthesis

If ATP is converted to ADP during photosynthesis, what happens to energy?

Energy is released to power endergonic reactions such as CO2 fixation

What is chemiosmosis in plants?

Using a proton gradient across thylakoid membranes to synthesize ATP

Why are photosynthesis and respiration essential for life on Earth?

They provide the flow of energy and recycle O2 and CO2 between organisms

What is the key difference between sexual and asexual reproduction?

Sexual reproduction involves two parents and produces genetically diverse offspring; asexual involves one parent and produces identical offspring

Name the major life-cycle events of sexually reproducing organisms.

Meiosis, gamete formation, fertilization, growth by mitosis

Why do cells carry out mitosis?

Growth, tissue repair, and asexual reproduction

Why do cells carry out meiosis?

To produce haploid gametes and promote genetic diversity

List the phases of the cell cycle.

G1, S, G2 (interphase) and M phase (mitosis/cytokinesis)

What happens during the S phase?

DNA is replicated

What are the three main cell-cycle checkpoints?

G1 checkpoint, G2 checkpoint, M (spindle) checkpoint

What conditions must be met to pass the G1 checkpoint?

Adequate nutrients, growth factors, proper size, intact DNA

What are cyclins?

Proteins whose concentrations fluctuate and activate Cdks to drive the cell cycle

What are Cdks (kinases) in the cell cycle?

Cyclin-dependent kinases that phosphorylate target proteins when bound to cyclins

What are growth factors?

External signaling molecules that stimulate cell division

What density-dependent factor inhibits cell division in crowded cells?

Contact inhibition

Give an example of a density-independent factor affecting the cell cycle.

Hormonal signals or nutrient availability unrelated to cell density

Define signal transduction.

Conversion of an external signal into a specific cellular response via a signaling cascade

Describe the basic structure of a chromosome.

DNA wound around histone proteins forming chromatin; condenses during division

Difference between a chromosome and a duplicated chromosome?

Duplicated chromosome has two sister chromatids joined at a centromere; a single chromosome has one chromatid

How do scientists count chromosomes?

By the number of centromeres present

What are histones?

Positively charged proteins around which DNA coils to form nucleosomes

Define sister chromatids.

Identical copies of a chromosome joined at the centromere after DNA replication

Define homologous chromosomes.

A pair of chromosomes with the same genes, one from each parent, possibly different alleles

What is a centromere?

Constriction where sister chromatids are attached

What is a centrosome?

Microtubule-organizing center containing centrioles in animal cells

What are kinetochores?

Protein complexes on centromeres where spindle fibers attach

Which cytoskeletal protein forms the mitotic spindle?

Microtubules (tubulin)

Which protein forms the contractile ring in animal cytokinesis?

Actin (with myosin)

Which human cells are diploid?

Somatic cells (2n = 46)

What is the haploid chromosome number in humans?

n = 23

What is binary fission?

Prokaryotic cell division involving DNA replication, segregation, and cytokinesis

How does binary fission differ from mitosis?

Prokaryotic, no spindle, simpler; mitosis is eukaryotic with spindle apparatus

List the phases of mitosis in order.

Prophase, prometaphase, metaphase, anaphase, telophase

What key event defines metaphase?

Chromosomes line up at the metaphase plate

How does cytokinesis differ in plants vs. animals?

Plants form a cell plate; animals form a cleavage furrow

If homologous chromosomes are separating, is the cell in mitosis or meiosis?

Meiosis I

How many copies of each gene are in a somatic cell?

Two copies (diploid)

How many copies of each gene does a gamete carry?

One copy (haploid)

After meiosis I, are daughter cells haploid or diploid?

Haploid

What is crossing over?

Exchange of DNA between nonsister chromatids of homologs during prophase I

Why is crossing over important?

Increases genetic variation in gametes

What is independent assortment?

Random orientation of homologous pairs at metaphase I, creating varied gamete combinations

What is a karyotype?

Photographic display of an individual’s chromosomes arranged in pairs

What information can a karyotype reveal?

Chromosome number, sex, large-scale abnormalities

Define nondisjunction.

Failure of homologs or sister chromatids to separate during meiosis, causing aneuploidy

What causes Down syndrome?

Trisomy 21 due to nondisjunction in meiosis I or II

List common signs of Down syndrome.

Characteristic facial features, developmental delay, heart defects, hypotonia

What maternal factor increases the risk of Down syndrome?

Advanced maternal age