Bio Final Exam Chat Review

What is photosynthesis?

The process by which autotrophs use sunlight to convert carbon dioxide and water into glucose and oxygen.

Equation:
6CO₂ + 6H₂O + Light Energy → C₆H₁₂O₆ + 6O₂

What is an autotroph?

An organism that makes its own food using sunlight or chemical energy (plants, algae, some bacteria).

What is a heterotroph?

An organism that obtains energy by consuming other organisms.

Which organelle performs photosynthesis? Describe its structure.

The chloroplast.

• Outer and inner membranes

• Thylakoids stacked into grana

• Chlorophyll located in thylakoid membranes

• Stroma = fluid surrounding thylakoids where the Calvin Cycle occurs

What are pigments?

Light-absorbing molecules used to capture solar energy.

Why are leaves green?

Chlorophyll reflects green wavelengths of light and absorbs mainly red and blue wavelengths.

What is chlorophyll?

The main photosynthetic pigment that absorbs sunlight.

What is ATP?

Adenosine Triphosphate—the cell's immediate energy source.

Structure:

• Adenine

• Ribose sugar

• 3 phosphate groups

Energy is released when the third phosphate bond breaks.

What is ADP?

Adenosine Diphosphate (ATP after losing one phosphate group).

ATP → ADP + Energy

How are ATP and glucose similar and different?

Similar: Both store energy.

Different:

• ATP = short-term energy storage

• Glucose = long-term energy storage

• ATP releases energy quickly

• Glucose must be broken down through cellular respiration

What is NADP+?

An electron carrier that transports high-energy electrons during photosynthesis.

What happens during the light-dependent reactions?

Location: Thylakoid membranes

Inputs:

• Sunlight

• Water

Outputs:

• ATP

• NADPH

• Oxygen (released)

What happens during the Calvin Cycle (light-independent reactions)?

Location: Stroma

Inputs:

• CO₂

• ATP

• NADPH

Outputs:

• Glucose

What factors affect photosynthesis rate?

• Light intensity

• Temperature

• Water availability

• Carbon dioxide concentration

What is cellular respiration?

The process that breaks down glucose to release usable energy (ATP).

Equation:
C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + ATP

What is the relationship between photosynthesis and cellular respiration?

Products of one are reactants of the other.

Photosynthesis:

• Makes glucose and oxygen

Cellular Respiration:

• Uses glucose and oxygen

Which organelle performs cellular respiration?

The mitochondrion.

What is aerobic respiration?

Respiration requiring oxygen.

What is anaerobic respiration?

Respiration occurring without oxygen.

Stage 1: Glycolysis

Location: Cytoplasm

Starts with: Glucose

Produces:

• 2 Pyruvate

• 2 ATP

• NADH

No oxygen required.

Stage 2: Krebs Cycle

Location: Mitochondrial matrix

Produces:

• CO₂

• NADH

• FADH₂

• 2 ATP

Stage 3: Electron Transport Chain

Location: Inner mitochondrial membrane

Produces:

• 32–34 ATP

• Water

Requires oxygen.

How many ATP are produced from one glucose molecule?

About 36 ATP total.

Why do you breathe harder during intense exercise?

To deliver more oxygen and remove excess carbon dioxide as ATP demand increases.

What is fermentation?

An anaerobic process that regenerates NAD+ so glycolysis can continue.

What type of fermentation occurs in humans?

Lactic acid fermentation in muscle cells.

What is alcoholic fermentation?

Fermentation performed by yeast and some microorganisms.

Produces:

• Ethanol

• CO₂

Used in bread-making and brewing.

What limits cell size?

• DNA overload

• Surface area-to-volume ratio decreases

What is the cell cycle?

The series of events leading to cell growth and division.

Stages:

• Interphase

• Mitosis

• Cytokinesis

What occurs during Interphase?

• Cell grows

• DNA replicates

• Organelles duplicate

Longest stage.

Prophase

• Chromatin condenses into chromosomes

• Nuclear membrane breaks down

• Spindle fibers form

Metaphase

Chromosomes line up in the center of the cell.

Anaphase

Sister chromatids separate and move to opposite poles.

Telophase

• New nuclei form

• Chromosomes uncoil

Cytokinesis

Cytoplasm divides, forming two daughter cells.

What is mitosis?

Cell division producing two genetically identical diploid cells.

Used for:

• Growth

• Repair

• Replacement

What is meiosis?

Cell division producing four genetically unique haploid gametes.

Sexual vs. Asexual Reproduction

Asexual

• 1 parent

• Fast

• No genetic variation

Sexual

• 2 parents

• More variation

• Slower

Diploid vs Haploid

Diploid (2n):

• Two chromosome sets

• Human body cells = 46

Haploid (n):

• One chromosome set

• Human gametes = 23

Which cells undergo mitosis and meiosis?

Mitosis:

• Somatic (body) cells

Meiosis:

• Germ cells in gonads (testes/ovaries)

What are homologous chromosomes?

Matching chromosome pairs containing genes for the same traits.

What is crossing over?

Exchange of DNA between homologous chromosomes during Prophase I.

Creates genetic variation.

What is a tetrad?

Pair of homologous chromosomes aligned together during Meiosis I.

What is nondisjunction?

Failure of chromosomes to separate properly during meiosis.

Example: Down syndrome (Trisomy 21).

Compare spermatogenesis and oogenesis.

Spermatogenesis:

• Produces 4 functional sperm

Oogenesis:

• Produces 1 egg + 3 polar bodies

Human chromosome numbers

• Skin cell = 46 chromosomes (2n, diploid)

• Sperm/Egg = 23 chromosomes (n, haploid)

What is genetics?

The study of heredity.

Gene, allele, trait

• Gene = segment of DNA coding for a characteristic

• Allele = alternative form of a gene

• Trait = observable characteristic

Genotype vs Phenotype

• Genotype = genetic makeup (TT, Tt)

• Phenotype = physical appearance (tall)

Homozygous vs Heterozygous

• Homozygous = TT or tt

• Heterozygous = Tt

Mendel's Principle of Dominance

Some alleles mask the effects of others.

Law of Segregation

Alleles separate during gamete formation.

Law of Independent Assortment

Genes for different traits separate independently during meiosis.

Cross: heterozygous tall red × homozygous white short

TtRr × ttrr

Phenotypes:

• 25% Tall Red

• 25% Tall White

• 25% Short Red

• 25% Short White

Ratio = 1:1:1:1

What inheritance pattern does a roan cow show?

Codominance (both red and white hairs expressed).

Examples of inheritance patterns

Incomplete dominance:

• Red × White flowers → Pink flowers

Codominance:

• Roan cattle

• AB blood type

Multiple alleles:

• ABO blood groups

Polygenic:

• Height

• Skin color

• Eye color

How is sex determined in humans?

Female = XX

Male = XY

Father determines sex by contributing either X or Y chromosome.

Why are males more likely to be colorblind?

Colorblindness is X-linked recessive. Males have only one X chromosome, so one recessive allele causes the condition.

What does DNA stand for?

Deoxyribonucleic Acid.

• Deoxy = lacking oxygen

• Ribo = sugar (deoxyribose)

• Nucleic = found in nucleus

Major roles of DNA

• Stores genetic information

• Replicates information

• Directs protein production

What is DNA's backbone?

Alternating deoxyribose sugars and phosphate groups.

Components of a nucleotide

• Phosphate group

• Deoxyribose sugar

• Nitrogenous base

DNA base pairing

• Adenine ↔ Thymine

• Cytosine ↔ Guanine

A-T and C-G

What is DNA's shape?

Double helix (twisted ladder).

What are antiparallel strands?

DNA strands run in opposite directions.

What is DNA replication?

The process of copying DNA before cell division.

What is DNA polymerase?

Enzyme that adds complementary nucleotides during replication.

Where is DNA located?

Eukaryotes:

• Nucleus

• Mitochondria

• Chloroplasts

Prokaryotes:

• Cytoplasm

What is RNA?

Ribonucleic Acid; helps convert DNA instructions into proteins.

Three differences between DNA and RNA

DNA	RNA

Double-stranded

Single-stranded

Deoxyribose

Ribose

Thymine

Uracil

mRNA

Carries genetic instructions from DNA to ribosome.

tRNA

Brings amino acids to ribosomes.

Contains anticodons.

rRNA

Forms ribosomes and helps build proteins.

What is transcription?

DNA → mRNA

Location:

• Nucleus

Enzyme:

• RNA polymerase

What is translation?

mRNA → protein

Location:

• Ribosome

Codon vs Anticodon

Codon:

• 3 bases on mRNA

Anticodon:

• Complementary 3 bases on tRNA

What is the genetic code?

The rules that determine which codons code for which amino acids.

Point mutation vs Frameshift mutation

Point Mutation:

• One nucleotide changed

Frameshift Mutation:

• Insertion/deletion shifts reading frame

• Usually much more severe

Final result of transcription + translation

A protein (polypeptide).

What is biotechnology?

The use of living organisms or biological processes to solve problems and improve products.

What is selective breeding?

Choosing organisms with desired traits to reproduce.

What is a transgenic organism?

An organism containing genes from another species.

What is gene therapy?

Replacing or correcting defective genes to treat disease.

What are concerns about GM foods?

• Possible environmental impacts

• Gene transfer to wild populations

• Ethical concerns

• Long-term health questions

What is cloning?

Producing genetically identical organisms.

Can life be patented?

Modified organisms and engineered genes may be patented, but this raises ethical and ownership concerns.

What three patterns of biodiversity did Darwin observe?

• Species vary globally

• Species vary locally

• Species vary over time

Why were Hutton and Lyell important?

They showed Earth is extremely old, giving evolution enough time to occur.

How do fossils support evolution?

They show extinct species and transitional forms linking ancient and modern organisms.

Natural Selection vs Evolution

Natural selection acts on individuals.

Evolution occurs in populations over generations.

What is fitness?

Ability to survive and reproduce successfully.

What is an adaptation?

An inherited trait that improves survival or reproduction.

Artificial selection vs Natural selection

Artificial Selection:

• Humans choose traits

Natural Selection:

• Environment chooses traits

Homologous structures

Similar structures from a common ancestor, even if functions differ.

Example:

• Human arm

• Whale flipper

• Bat wing

Analogous structures

Same function but different evolutionary origins.

Example:

• Bird wing and insect wing

Vestigial structures

Reduced structures inherited from ancestors.

Example:

• Human appendix

• Whale pelvis

What is biogeography?

Study of species distribution across Earth.

What is genetic drift?

Random changes in allele frequencies, especially in small populations.

What is a gene pool?

All genes and alleles present in a population.

What is allele frequency?

How common an allele is within a population