Lactose Digestion and Intolerance

Foods that do have lactose include milk, yogurt, and cheese. Foods that don't include lactose are plant-based milk like oat milk.

Lactose intolerance is the inability to digest lactose. Lactase persistence is the ability to digest lactose into adulthood.

Kanna and her mother are lactose intolerant. Kanna's baby brother and Alissa are lactase persistent.

The most lactose intolerant regions are Africa, Asia, and Latin America. North Europe tends to be least lactose intolerant.

Lactose is a disaccharide made of two monosaccharides: glucose and galactose. When lactose is digested, it is broken down by the enzyme lactase into these two simpler sugars, which are then absorbed into the bloodstream.

In people who can digest lactose, glucose and galactose are present. In those who cannot, lactase is low or absent, and lactose remains undigested.

The Lock-and-Key diagram shows how an enzyme (the "lock") and its specific substrate (the "key") fit together. The substrate binds to the enzyme's active site, allowing a chemical reaction to occur.

Lactose is digested through a process called hydrolysis. During hydrolysis, the enzyme lactase breaks down lactose into its two monosaccharide components, glucose and galactose, by adding a water molecule. The water molecule helps split the bond between the glucose and galactose.

Symptoms of lactose intolerance include bloating, gas, diarrhea, stomach cramps, and nausea after consuming dairy products.

Humans are unique among mammals because many continue to consume milk into adulthood, a behavior known as lactase persistence, whereas most mammals stop drinking milk after weaning.

An enzyme is a protein that speeds up chemical reactions in the body. It works by binding to a substrate (the molecule it acts on) at its active site, facilitating a chemical reaction to convert the substrate into a product. Increasing enzyme or substrate concentration increases reaction rate, but only up to a point where the enzyme becomes saturated.

High temperatures can denature enzymes, while low temperatures slow down reactions. Each enzyme has an optimal pH; extreme pH levels can disrupt the enzyme's structure.

The Central Dogma of molecular biology states that genetic information flows from DNA to RNA to protein. It describes how DNA is transcribed into RNA, which is then translated into proteins that perform cellular functions.

While some individuals are lactose intolerant, they still have the DNA code for lactase. The only difference observed among all individuals was that one of the individuals upstream code has one base difference compared to everyone else. There are no visual differences in the structure of chromosome 2 for all individuals.

DNA is structured as a double helix, with two strands made of nucleotides. Each nucleotide consists of a phosphate group, a sugar (deoxyribose), and a nitrogenous base (adenine [A], thymine [T], cytosine [C], and guanine [G]). The strands are connected by base pairs: A with T and C with G. During DNA replication, the double helix unwinds, and the enzyme helicase separates the strands. DNA polymerase adds complementary nucleotides to each strand, forming two identical DNA molecules. To synthesize a complementary strand:For a template strand like 5'-ATGC-3', the complementary strand would be 3'-TACG-5'.

Coding DNA makes up about 1-2% of the human genome and provides instructions for making proteins. Non-coding DNA makes up about 98-99% and doesn't code for proteins, but helps regulate gene expression, organize chromosomes, and maintain DNA. Regulatory sequences in non-coding DNA control when and how genes are turned on or off, which is crucial for cell function and development.

Gene regulation refers to the processes that control the timing, location, and amount of gene expression. Transcription factors are proteins that bind to specific DNA sequences near genes to regulate their transcription. They can either activate or repress gene expression by facilitating or hindering the binding of RNA polymerase to the gene, thus controlling its transcription into RNA.

Some people can digest lactose into adulthood due to lactase persistence, a condition where the body continues to produce lactase (the enzyme that breaks down lactose). This is considered the mutant condition, as most adults have low lactase production and are lactose intolerant (the normal condition). Lactase persistence evolved in populations that relied on dairy farming, providing a survival advantage by allowing adults to digest milk.

No, a lactose intolerant person cannot get over their condition by consuming more dairy. Lactose intolerance occurs due to a lack of lactase enzyme, and consuming more dairy does not increase lactase production. In fact, it can worsen symptoms like bloating, gas, and diarrhea.

measures a solution's acidity or alkalinity, ranging from 0 (acidic) to 14 (alkaline), with 7 being neutral.

Proteins that accelerate chemical reactions in living organisms.

The substance upon which an enzyme acts during a reaction.

A sugar found in milk, made up of galactose and glucose

An Enzyme that breaks down lactose into glucose and galactose.

A chemical reaction in which water is used to break down molecules, splitting them into smaller parts.

A process where two molecules are joined together by removing water.

The process of copying DNA into RNA.

The process of converting mRNA into a sequence of amino acids to form a protein.

the enzyme that synthesizes RNA

where the gene expression begins

a "decision" is made about which genes to activate

2 types of regulatory proteins, control whether a gene is active

a repressor protein prevents transcription

an activator protein binds to stimulate transcription

Excess fat provides energy reserves for growth, supports brain development, and helps maintain body temperature in newborns.

Leptin is a hormone secreted by adipose (fat) tissue that helps regulate energy balance and appetite by signaling the brain about fat storage levels.

Excess fat increases leptin levels, which can lead to leptin resistance, disrupting appetite regulation and contributing to obesity.

Studies show that high-fat diets can alter leptin signaling, causing leptin resistance and affecting energy balance and fat storage.

Transcription converts DNA to mRNA, while translation synthesizes proteins from mRNA; both processes occur in the nucleus and ribosomes, respectively.

Transcription involves copying a DNA sequence into mRNA, and translation uses mRNA to assemble amino acids into a protein at the ribosome.

The codon table and wheel are tools to determine which amino acids correspond to specific codons in an mRNA sequence.

Leptin resistance occurs when the brain does not respond to leptin, often due to genetic and environmental factors like diet and obesity.

DNA is double-stranded with thymine, stores genetic information, while RNA is single-stranded with uracil, and helps in protein synthesis.

DNA has thymine (T), and RNA has uracil (U) because RNA's structure uses uracil to pair with adenine instead of thymine.

The sequence of amino acids determines the protein's structure and function, and errors can lead to misfolded or dysfunctional proteins.

Proteins are polymers made of amino acid monomers; proteins and amino acids differ in their structure, with proteins having complex structures like primary, secondary, tertiary, and quaternary forms.

Primary structure is the amino acid sequence, secondary structure is the folding into alpha-helices and beta-pleated sheets, tertiary is the 3D shape, and quaternary is multiple polypeptides.

Lipodystrophy is a disorder where fat storage is abnormal, leading to fat loss in some areas and accumulation in others, often associated with leptin deficiencies.

Epigenetics refers to changes in gene expression due to environmental factors, which can affect an organism's traits and potentially be passed on to future generations.

Epigenetic modifications can alter leptin gene expression, influencing its role in fat storage, hunger regulation, and obesity susceptibility.

Global obesity rates are rising due to factors like poor diet, sedentary lifestyle, genetics, and environmental influences, with individual variation in fat storage due to genetic and lifestyle factors.

Excessive body fat that negatively impacts health.

A standard diet used for comparison in experiments.

A diet high in fructose, often from sugary foods, linked to health risks.

A diet rich in fats, often leading to weight gain and health issues.

Changes in gene expression caused by factors other than DNA sequence.

When the body doesn't respond properly to leptin, leading to overeating.

Chemicals that promote weight gain or fat storage.

Based on observed or experimental evidence.

Mimosa pudica exhibits nyctinasty, where its leaves fold at night and open during the day in response to light and darkness.

Urban humans tend to have more segmented and shorter sleep cycles due to artificial light, while indigenous communities often follow more natural, longer sleep patterns aligned with the sun's cycle

Circadian rhythms are 24-hour cycles that regulate physiological processes like sleep, feeding, and hormone release, impacting daily behavior and seasonal changes.

Melatonin is a hormone secreted by the pineal gland that regulates sleep-wake cycles by promoting sleepiness in response to darkness.

Cortisol is a hormone released by the adrenal glands, peaking in the morning to help wakefulness and decreasing in the evening to prepare the body for sleep.

Body temperature typically decreases during sleep at night and rises in the morning, following a circadian pattern to promote wakefulness.

Light, especially blue light, helps reset the body's internal clock, promoting wakefulness, with blue light specifically influencing the wake cycle.

Blue light exposure suppresses melatonin release, making it harder to fall asleep and disrupting sleep cycles, especially when used before bed.

Poor sleep can lead to cognitive impairments, increased stress, and health issues like obesity and cardiovascular disease, with technology (e.g., screens) exacerbating these effects by interfering with sleep.

A hormone that regulates sleep-wake cycles, promoting sleepiness in response to darkness.

The regular pattern of heartbeats controlled by the body's internal clock, often synchronized with circadian rhythms.

A hormone released in response to stress, helping regulate sleep, metabolism, and immune function, with levels peaking in the morning.

Mismatch diseases are health conditions that arise when human bodies are poorly adapted to modern environments, often due to rapid lifestyle or environmental changes. Examples include obesity, leptin resistance, and lactose intolerance.

A common ancestor is an organism from which two or more species are descended.

Matches in amino acid sequences between organisms suggest that they share a common ancestor, with more similarities indicating a closer evolutionary relationship.

Times of divergence show when different species branched off from a common ancestor, helping us understand how humans are related to other organisms through evolutionary history.

Data from amino acid sequences and divergence times help scientists track the evolutionary pathways and relationships among species, showing how they evolved from a common ancestor over time.

Lines of evidence include fossil records, comparative anatomy, embryology, and molecular biology (e.g., DNA sequences). These show how species share common traits inherited from a common ancestor.

A fossil is the preserved remains or traces of organisms from the past. Scientists use fossils to study ancient life forms and understand evolutionary changes.

Anatomy is the study of the structure of organisms and their parts.

An embryo is the early developmental stage of an organism.

It can be difficult to determine an embryo's species, as embryos of many organisms look similar early in development.

The eye evolved through gradual improvements over time, from light-sensitive cells in bacteria to complex organs in modern species. The limitations of human eyes are due to evolutionary compromises and design constraints.

Comparative anatomy looks at similarities in the structure of different organisms to infer common ancestry, including similarities in embryos.

A family tree shows evolutionary relationships. A clade is a group of organisms with a common ancestor. A lineage is a continuous line of descent. Scientists build phylogenetic trees by comparing genetic, morphological, and fossil data.

A speciation event is when a single species splits into two or more distinct species. This can occur due to geographic isolation or environmental changes.

Evolution goes in one direction, which is forward; changes in features are gradual and accumulate over time, and new features evolve on existing structures.

Darwin's phrase "descent with modification" means that species change over time through small genetic variations passed down from ancestors.

Evolution occurs in trees because species diverge into branches, not in a straight line (ladder), reflecting branching patterns of evolutionary history.

Glycolysis is a universal metabolic pathway found in almost all living organisms, suggesting it originated in a common ancestor.

We don't just evolve to address mismatch problems because evolution works over long periods and is influenced by a variety of factors, not just immediate environmental pressures.

the similarity resulting from common ancestry

anatomical resemblances that represent variations on a structural theme present in a common ancestor

Belong to the group called tetrapod

the scientific study of the geographic distribution of species, provides evidence of evolution

when Earth's continents were all one united

species that are not found anywhere else in the world