Biology Test April 2014

  • Created by: Foxic
  • Created on: 17-04-14 16:48

Recommendations for food groups, why, Atkins?

Carbohydrates: Very little. Encourages body to burn fat instead of glucose

Protein: Eat more. Increases metabolism, has a less effect on insulin, and a greater effect on glucagon.

Fat: Eat more. Reduces carbohydrates craving, accelerates the burning of fat (dietary & stored).

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Phases of the Atkins diet?

1. Introduction

2. Ongoing weight loss

3. Pre-maintenance

4. Maintenance

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Goal of 'Introduction' phase, Atkins?

  • Switch the fuel the body uses from carbs (glucose) to fat (including body fat)
  • Jump-start weight loss
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Goal of 'Ongoing Weight Loss', Atkins?

  • Gradually increase the intake of net carbs beginning with 25g
  • Slowly increase the variety of different foods eaten, normally starting with a small portion of nuts/seeds, or some foundation vegetables
  • Obtain the level of intake of carbs for losing weight
  • Deciding when to move onto the next phase
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Goal of 'Pre-Maintenance,' Atkins?

  • Lose the last 4.5kg, to test carb tolerance
  • Test which foods can be consumed without increasing in weight
  • Find the carbohydrate balance
  • Maintain weight
  • Control intake of food
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Goal of 'Maintenance,' Atkins?

  • Maintain the diet
  • Make it into a lifestyle
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Scientific support for the Atkins diet

  • Clear loss of weight, when body goes into ketosis (short-term studies)
  • Not enough long-term studies to be conclusive
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Scientific evidence against the Atkins diet

  • Severely negatively impacts the metabolism. Eg. elevated levels of low-density lipoproteins
  • Adverse emotional effects
  • Study shows that ketogenic diets can be harmful
  • MUST be conducted under the supervision of a medical professional
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What does the GI represent?

  • The corresponding capacity of a carbohydrate food to increase the level of glucose in the blood compared to a reference food. 
  • Scale from 1-100
  • Founded on how fast digested carbohydrates affect the blood sugar levels
  • The higher the number, the worse the GI value is
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Recommendations for food groups, why, eg, GI?

  • Carbohydrates: 'Good' carbs, low GI value. Eg. carrots, brown rice, apples, pears
  • Proteins: High proteins. Eg. Eggs, beans
  • Fat: Small amounts. Don't add oil or butter
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Scientific support for the GI diet

  • Suitable for people with high blood sugar levels
  • Suitable for people who want to teach themselves to feel full faster. Lower GI value, fuller for longer
  • Reduce chances for type 2 diabetes
  • Maintaining a healthy heart
  • Preventing cancer, due to the diet limiting obesity
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Scientific evidence against the GI diet

  • Not beneficial if you want to lose weight
  • Sometimes hard to determine the GI value of a food, eg. whether the food is fried, what type of oil used, etc.
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Recommendations for food groups, why, eg, 5:2?

No exact specifications as long as you stay under a certain number of calories per day.

  • 500 for women
  • 600 for men
  • Eat some for a healthy balance
  • Skip simple carbs. Eg. pasta, rice, juice, flour. They increase hunger pangs/feelings
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Phases of 5:2 diet?

  • 5 days of eating regular food
  • 2 days of fasting, eating extremely low amounts of calories
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Scientific support for the 5:2 diet?

  • When you eat 500 calories per day, for 2 days, the body goes into fasting mode, and lowers the metabolism
  • Risks for cancer, mental illnesses, and Alzheimers increases
  • Amount of IGF1 in the body decreases
  • Less calories, better fat burning properties
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Scientific evidence against the 5:2 diet?

  • Not recommended for diabetics
  • Not recommended for people with low BMIs
  • Fasting does not always make you lose weight
  • Weight can go up when you start eating again
  • When fasting, a chemical 'enemas' become more common in the intestine, reducing the good bacteria in the process
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Recommendations for food groups, why, eg, LCHF?

  • Carbohydrates: Eliminated. Replace with avocado, brocolli, mushrooms, cauliflower
  • Proteins: High amounts, to replace carbs. 
  • Fats: High amounts
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Scientific support for the LCHF diet?

  • Adapted to eat protein & fat. Not originally designed to eat carbs
  • Difficult to overeat on the LCHF diet, lose weight without hunger
  • Since low fat products were released in Sweden (1989), the obesity percentage has gone from 5%-14%.
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Scientific evidence against the LCHF diet?

  • Best to have a balanced diet, and to not exclude anything from it
  • You dont' eat enough fiber, leading to constipation and bacteria in the intestine
  • Side effects: Headaches, nausea, tiredness
  • Not enough long-term studies
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Recommendations for food groups, why, eg, low fat

  • Carbohydrates: Can be eaten as normal. Eg. whole grain, vegetables, fruits
  • Protein: Eat as normal, stay away from red meat. Eg. chicken, beans.
  • Fat: Eat low-fat products. Fat consumption under 30% each day.
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Scientific support for the low fat diet?

  • Made to run off glucose from carbs. With this diet, because you are allowed to eat carbs, you avoid side effects eg. brain fog.
  • Health benefits. Eg.decrease chances of cancer, cardiac conditions, having a stroke.
  • Easy to follow
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Scientific evidence against the low fat diet?

  • Lacking vitamins A, E, K that are found in fats. Therefore you need to eat some fats to stay healthy, or take a pill
  • Fat free food = taste free food. Leads to overeating to make up for the lack of satisfaction taste-wise
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Recommendations for food groups, why, eg, raw food

  • Carbohydrates: Eat normally. Eg. Fruits, starches, grains
  • Proteins: Gained mainly from germinated nuts, seeds, grains, leafy veg.
  • Fats: Nuts, seeds, avocado, coconut better.
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Scientific support for the raw food diet?

  • People claim to feel better and full of energy
  • More enzymes, because it's only heated to 40C.
  • Cooked food contain toxins, that can cause an increase in weight
  • Processed foods also contain chemicals that are bad for the body
  • Raw foods have higher nutrient values
  • Raw foods have a higher number of antioxidants, eg. stifling signs of aging, reducing the risk of cancer
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Scientific evidence against the raw food diet?

  • When you cook foods, you release nutrients due to the breakage of fibers and cellular walls, which wouldn't be available from the same raw food, which narrows the nutrient diversity
  • Cooking reduces certain chemicals in a vegetable that inhibit the absorption of minerals
  • Humans make their own digestive enzymes to digest food, so saying that cooking food is bad because it destroys enzymes is unreasonable
  • Plant enzymes in raw food get destroyed due to the acids in the hyman gut
  • Raw food supporters say that no other animals cook their food, but no other animals put their food in a blender to make it more digestible
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Recommendations for food groups, why, eg, Stone Ag

  • Carbohydrates: Forbidden, particularly those containing processed sugars.
  • Proteins: Eat lots. Eg. high-quality game meats, consumption of veg, fruit, roots, nuts
  • Fats: High-fat substances forbidden. Eg. Milk, dairy products
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Phases of the Stone Age diet?

No phases persay.

  • 1st: 'Adjustment period' for a couple days to a few weeks. Due to exclusion of carbs
  • Eat plenty of sat fats, members of the brassicas family, extra vitamin supplements.
  • Drink lots of water
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Scientific support for the stone age diet

  • Humans haven't shown any singificant sings of evolutionary development, and therefore should return to our previous Paleolithic hunter-gatherer diet. We have only been farmers for a short period of time
  • QED: We haven't had the time to adapt to this agricultural shift
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Scientific evidence against the stone age diet

  • Lack of long-term studies
  • Humans have developed and adapted to other diets and are not just stuck with the Paleolithic diet
  • Large increase in the consumption of dairy products. Eg. People in Europe have a strong tolerance for lactose
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Recommendations for food groups, why, eg, vegan?

  • Carbohydrates: Important to get. Eg. whole grain products, as they contain protein, iron, vitamin B, anti-oxidants
  • Protein: Eat a normal amount. Eg. beans, nuts, mushrooms, soy products
  • Fats: Try to not eat so much. Easy for vegans to get too much fat (need to eat plant oil to get vitamins), 15-20% recommended. Eg. avacado, nuts/seeds, olives, vegetable oils
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Scientific support for the vegan diet?

  • Consumers of animal protein are more prone to suffer from heart disease, diabetes, certain cancers
  • Vegan diet contains more fibre, different types of protein, vitamins
  • Vegan diet is lower in calories, saturated fats, and cholesterol
  • Vegan diet useful for increasing intake of protective nutrients, minimizes intake of dietary factors present in several chronic diseases
  • Many plants proven to influence chronic disease reduction
  • Vegans have a decreased risk of cancer
  • Obesity lower amongst vegans
  • Vegans have lower cholesterol, lower blood pressure
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Scientific evidence against the vegan diet?

  • Vitamin/mineral deficiencies. Vegans must find alternative sources to many vitamins, as they are only found in animal products
  • Difficulty when dining out, and grocery shopping
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Recommendations for food groups, why, eg, VLCD?

  • Carbohydrates: Low amount.
  • Protein: Small amounts are acceptable, as long as its of low calories
  • Fats: Not recommended.

The aim is to eat under 800kCal a day, to stay in a state of ketosis

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Phases of the VLCD diet

  • During the first few days, ketosis sets in
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Scientific support for the VLCD diet?

  • VLCD's often sold as Supplement Packets, eliminates choice, psychological benefit
  • Easy to follow
  • Benefits for patients of BMIs of 28-30
  • Decreased risk of cardiovascular disease, lower fasting glucose levels, triglycerides, and LDL lipoproteins
  • Weight loss very rapid, 1.5-2.5kg per week
  • Life saving for morbidly obese patients
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Scientific evidence against the VLCD diet?

  • Nausea, hair loss, dizziness, dry mouth, migraines, fatigue, irritable skin, cold intolerance, menstrual irregularities, constipation, gallbladder problems, and diarrhea 
  • Psychosis
  • VLCDs can only be done with medical oversight, only recommended for those with harsh obesity issues
  • VLCDs not successful long term, users shoot up in weight
  • Lack of nutrients needed, leading to increased riks of other types of diseases.
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The mouth as part of the digestive system

  • Mastication increases the surface area
  • Saliva fulfills 2 functions:
  • Moistening and lubricating the food
  • Starting carbohydrate digestion, with salivary amylase
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The oesophagus as part of the digestive system

  • Controlled by sphincter at stomach border
  • Moves food by peristalsis
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The stomach as part of the digestive system

  • Normal volume: 2 litres
  • Food stays in here for 2-6 hours
  • Secretions from the stomach include mucus, HCl, and pepsin, etc
  • Gastric juices bring the stomach pH to 2
  • Epithelial cells are renewed every 3 days due to stomach acidity 
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The duodenum as part of the digestive system

  • 20-30cm long
  • Secretions include bile salts, bilirubin, bicarbonate ions, and pancreatic amylase (has to be secreted twice as it gets denatured in the stoamch)
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The ileum as part of the digestive system

  • 6m long
  • Site of absorption
  • Surface area 300m squared
  • This is due to folds, aka villi (0.5-1.5mm) , and micro villi (1 micrometre)
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Diagram of the villi


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The large intestine/colon as part of the digestive

  • 1m long
  • Reabsorbs about 7 litres of water every day from stomach content
  • Bacteria (E. Coli) produce Vitamin K
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The rectum as part of the digestive system

  • Short term storage before defecation
  • Controlled by 2 sphincters; one involuntary, and the other voluntary
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Describe the process of breathing

Air passes through:

1. The nasal cavity, where it is moistened and warmed. Gristle removes particles & droplets.

2. The pharynx

3. The larynx

4. The trachea

5. The bronchi

6. The bronchi divide into bronchioles (no more gristle by this point)

7. The bronchioles split into alveoli

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What surrounds the lungs? Not the ribs.

  • Each lung is cobered in 2 sheets of tissue
  • One fits snugly over the lung
  • The other is attached to the inside of the thorax
  • Between them is a layer of lubricating fluid
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Describe the process of inspiration

1. The ribcage swings outward

2. The diaphragm is lowered

This causes a larger volume between the sheets covering the lungs.

Larger volume = lower pressure, causing the lungs to expand, sucking in air from the outside

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Describe the process of expiration

1. The ribcage, and diaphragm relaxes

This leads to a decrease of volume of the thorax.

A smaller volume causes higher pressure, causing air to be expelled from the lungs.

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Describe the process of gaseous exchange

1. The CO2 produced in respiration is transported to the lungs

2. The CO2 diffuses from the capillaries into the air in the alveoli, to be expired

3. The oxygen diffuses from the alveoli to the capillaries

4. The oxygen attaches to the haemoglobin

5. The haemoglobin takes the oxygen to the cells of the body

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What is the point of the circulatory system?

  • Ensures that all cells of the body are supplied with oxygen, energy, and building blocks
  • Removing cellular waste
  • Blood vessels pass by every cell, and support them
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Diagram of the heart


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How does blood move through the heart?

1. Deoxygenated blood gathers in the right atrium, through the superior vena cava

2. One stroke-full of blood is moved into the right ventricle, through the tricuspid valve

3. The right ventricle contracts and sends the blood to the lungs to be oxygenated, through the pulmonary valve, and artery

4. Oxygenated blood completes the small circuit by entering the left atrium, through the pulmonary vein

5. The blood enters the left ventricle through the mitral valve

6. The left ventricle contracts and sends the blood through the aortic valve, and out through the aorta

7. The oxygenated blood is sent out to the body at a high pressure

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Characteristics of veins

  • Not as elastic as arteries
  • Wider
  • Thinner walls
  • Less muscular
  • Valves to prevent blood from flowing backwards
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Characteristics of capillaries

  • Tiny blood vessels
  • Walls 1 cell thick
  • Permeable
  • Surrounded by tissue fluid
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Characteristics of arteries

  • Wide blood vessels
  • Carries oxygenated blood from the heart to the body
  • Elastic tissue
  • Muscle fibres
  • Elastic tissue snapping back into place causing what we can feel as a pulse
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What does the tissue fluid do?

  • Similar to plasma, but contains less protein
  • It bathes all the living cells of the body
  • Contains dissolved food and oxygen from the blood, ergo supplies oxygen with all of its needs
  • It eventually seeps back into the capillaries, after having received the waste products of the cells
  • The waste is carried away by the blood stream
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Describe the process of clotting

1. Wounds in blood vessels release clotting factors

2. These factors cause fibrinogen to form fibrin threads

3. Fibrin threads form webs 

4. These webs catch red blood cells, and platelets, and form a scab

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Characteristics of B-lymphocytes

  • Formed in the bone marrow
  • Produce antibodies
  • Plasma cells
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Characteristics of T-lymphocytes

  • Produced in the thymus
  • "Killer" T-cells attach to marked (with antibodies) cells, and kill them
  • "Helper" T-cells stimulate B-cells & phagocytes
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Describe passive immunity

  • Antibodies produced by someone else, that has recovered from a disease
  • Serum (blood plasma w/o fibrinogen) that is injected into people as a vaccine
  • Snake serum is produced by horses
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Describe innate immunity

  • Antibodies inherited from mother's breast milk
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Describe natural acquired immunity

  • Antibodies for a certain disease are remembered by memory cells, stored in lymph nodes
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Describe artificially acquired immunity

  • A weakened pathogen is injected via a vaccine into a subject
  • Antibodies are formed in the subject
  • This creates memory cells, stored in the lymph nodes
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