carbohydrates Flashcards
Carbohydrates
Except for milk sugar (lactose) and small amounts of glycogen in meats, all the carbohydrates—sugars and starches—we ingest are derived from plants. Sugars come mainly from fruits, sugar cane, and milk. The polysaccharide starch is found in grains, legumes, and root vegetables. The polysaccharide cellulose, which is plentiful in most vegetables, is not digested by humans, but it provides fiber that increases the bulk of the stool and aids defecation.
Lipids
Although we also ingest cholesterol and phospholipids, most dietary lipids are triglycerides (neutral fats). We eat saturated fats in animal products such as meat and dairy foods and in a few plant products, such as coconut. Unsaturated fats are present in seeds, nuts, and most vegetable oils. Major sources of cholesterol are egg yolk, meats, and milk products.
Proteins
Animal products contain the highest-quality proteins, molecules that are amino acid polymers. Eggs, milk, fish, and most meat proteins are complete proteins that meet all of the body’s amino acid requirements for tissue maintenance and growth.Legumes (beans and peas), nuts, and cereals are also protein rich, but their proteins are nutritionally incomplete because they are low in one or more of the essential amino acids. The essential amino acids are the eight amino acids (listed in Figure 14.18) that our bodies cannot make. Hence we must obtain these amino acids from our diet. As you can see, strict vegetarians must carefully plan their diets to obtain all the essential amino acids and prevent protein malnutrition. Cereal grains and legumes when eaten together provide all the needed amino acids, and some variety of this combination is found in the diets of all cultures (for example, rice and beans). Soy and quinoa ([keen′-wah], a seed but classified as a whole grain) are also sources of complete plant-based proteins.
Vitamins
Vitamins are organic nutrients of various forms that the body requires in small amounts. Most vitamins function as coenzymes (or parts of coenzymes); that is, they act with an enzyme to accomplish a particular type of catalysis.
Although vitamins are found in all major food groups, no one food contains all the required vitamins. Thus, a balanced diet is the best way to ensure a full vitamin complement, particularly because certain vitamins (A, C, and E) appear to have anticancer effects. Diets rich in broccoli, cabbage, and brussels sprouts (all good sources of vitamins A and C) appear to reduce cancer risk. However, whether vitamins can work wonders is a controversial issue.
Minerals
The body also requires adequate supplies of seven minerals (which are inorganic substances)—calcium, phosphorus, potassium, sulfur, sodium, chloride, and magnesium—as well as trace amounts of about a dozen others.
Fats and sugars have practically no minerals, and cereals and grains are poor sources. The most mineral-rich foods are vegetables, legumes, milk, and some meats.
The section on metabolism discusses the main uses of the major nutrients in the body. (Appendix D details some important roles of vitamins and minerals in the body.)
Metabolism
(mĕ-tab′o-lizm; metabol = change) is a broad term referring to all chemical reactions that are necessary to maintain life. It involves catabolism (kah-tab′o-lizm), the breakdown of substances to simpler substances, and anabolism (ah-nab′o-lizm), the building of larger molecules or structures from smaller ones. During catabolism, bond energy of foods is released and captured to make adenosine triphosphate (ATP), the energy-rich molecule used to energize all cellular activities, including catabolic reactions.
Not all foodstuffs are treated in the same way by body cells.
Not all foodstuffs are treated in the same way by body cells. For example, carbohydrates, particularly glucose, are usually broken down to make ATP. Fats are used to build cell membranes, make myelin sheaths around neurons, and insulate the body with a fatty cushion. They are also used as the body’s main fuel for making ATP when there are inadequate carbohydrates in the diet. Proteins are the major structural materials used for building cell structures.
Carbohydrate Metabolism
Imagine This: Your Body = A Campfire
You need fuel to keep the fire going, right?
In your body, that fuel is glucose, which comes from carbs (bread, rice, fruit, etc.).
So What Happens to Glucose in the Body?
You eat carbs → they turn into glucose (sugar).
Your cells take that glucose and “burn” it to make energy.
The kind of energy your body uses is called ATP (it’s like battery power).
This whole “burning” process = cellular respiration 🔥
The 3 Easy Steps of Cellular Respiration:
You don’t need to remember big words—just know what happens.
Step What Happens Where
1. Glycolysis Break glucose in half In the cytoplasm
2. Citric Acid Cycle Break it down more In the mitochondria
3. Electron Transport Chain Make LOTS of ATP In the mitochondria
💡 Oxygen is needed at the end to help finish the process. That’s why we breathe!
What Comes Out?
ATP = energy 💥
Carbon dioxide (CO₂) = you breathe it out 😮💨
Water (H₂O) = your body uses it 💧
What’s the Liver Got to Do With It?
Your liver helps manage how much glucose is in your blood.
It can store extra sugar, or make sugar when you need it.
It can even use fat instead, so the rest of your body has more glucose to use (the liver is generous like that 😄).
Summary (Super Simple):
You eat carbs → they turn into glucose.
Your cells use glucose to make energy (ATP).
This process needs oxygen and happens in steps.
You get energy, and the leftovers are CO₂ and water.
Your liver helps keep blood sugar balanced.
of how your body turns sugar into energy.
