es,haemoglobi and so on..
The body will break down muscles and organ,in order to feed the protein hunger,if protein intake is not sufficient.

Q:Guidelines For Protein Intake
Recommended Dietary Allowance(RDA) of protein is 0.8 gram per kilogram of body weight per day for men and women ages 19-70.However this will be vary depends on the sport u play.
Athletes:1.4-2.0 grams per kilogram of body weight.
Check below to have a roughly how much protein u should take in per day:

150 pounds = 105 - 135 grams of protein a day
160 pounds = 112 - 144 grams of protein a day
170 pounds = 119 - 153 grams of protein a day
180 pounds = 126 - 162 grams of protein a day
190 pounds = 133 - 171 grams of protein a day
200 pounds = 140 - 180 grams of protein a day
220 pounds = 154 - 198 grams of protein a day
240 pounds = 168 - 216 grams of protein a day
260 pounds = 182 - 234 grams of protein a day
To calculate Apply this formula:
Weight in Pounds x %body fat=A
Weight in Pounds -A=B
B x .9 =Protein intake

For example,
I am approximately 145 pounds,body fat 15%
155 x 0.15=23.25
155-23.25=131.75
131.75 x .9=118.575 grams of protein per day.

To Calculate % of fat
Read everything carefully.It is simple

For Men:
Before you use the formulas, there are two measurements that are required:

Measurement 1: Bodyweight

Measurement 2: Waist Girth (measured at the umbilicus)

Procedure:
1) Multiply your bodyweight by 1.082. Add the result to 94.42. Once your calculation is complete, save the number. à (Bodyweight x 1.082) + 94.42=Result 1

2) Multiply your waist girth by 4.15. Once you get this result, subtract it from the number obtained in step 1 (ie: Step 1 result-Step 2 result). The result obtained after the subtraction is done is your lean bodyweight (your weight if you had no fat in your body at all). à Result 1 - (Waist Girth x 4.15)= Lean Body Weight

3) Finally, subtract your lean bodyweight from your total bodyweight (Total weight-Lean Bodyweight). Once you get the result, multiply that number by 100. Once you get the result divide it by your total bodyweight. This final result is your percentage of body fat. à ((Total Bodyweight - Lean Bodyweight) x 100) divided by (Your Body Weight) = Your Percentage of Body Fat.

Example:
I weigh 190 and I have a 30.5inch waist. Therefore, step 1 is (190 x 1.082) + 94.42 = 300. Step 2 says that my lean body weight equals 300-(30.5 x 4.15)=173.425. Finally, Step 3 says that my body fat percentage is ((190-173.425) x 100) divided by 190= 8.72%.

For Women:
Before you use the formulas, there are five measurements that are required (not fair, I know):

Measurement 1: Bodyweight.

Measurement 2: Wrist Circumference (measured at the widest point).

Measurement 3: Waist Circumference (measured at your umbilicus).

Measurement 4: Hip Circumference (measured at the widest point).

Measurement 5: Forearm Circumference (measured at the widest point).

Procedure:
1) Multiply your bodyweight by 0.732. à Bodyweight x .0732 = Result 1.

2) Add the result above to 8.987. à Result 1 + 8.987= Result 2.

3) Divide your wrist circumference by 3.14. à Wrist divided by 3.14 = Result 3.

4) Multiply your waist measurement by 0.157. à Waist x 0.157 = Result 4.

5) Multiply your hip measurement by 0.249. à Hip x 0.249 = Result 5.

6) Multiply your forearm measurement by 0.434. à Forearm x 0.434 = Result 6.

7) Add results 2 & 3. à Result 2 + Result 3 = Result 7.

8) Subtract Result 4 from Result 7. à Result 7 - Result 4 = Result 8.

9) Subtract Result 5 from Result 8. à Result 8 - Result 5 = Result 9.

10) Add Result 6 and Result 9. The result is your lean body mass (your fat free weight) à Result 6 + Result 9 = Lean Body Mass.

11) Subtract your lean body mass from your bodyweight. Once you get the result, multiply that number by 100. Once you get this result, divide it by your bodyweight. à ((Bodyweight-Lean Body Mass) x 100) divided by your bodyweight.

Example:
A woman that weighs 125, and has a wrist measurement of 6.0, a waist measurement of 24, a hip measurement of 38, and a forearm measurement of 9.5 would calculate her body fat percentage in the following manner. Step 1: 125 x 0.732=91.5. Step 2: 91.5 + 8.987=100.487. Step 3: 6 divided by 3.14=1.91. Step 4: 24 x 0.157=3.768. Step 5: 38 x 0.249=9.462. Step 6: 9.5 x 0.434=4.123. Step 7: 100.487+1.91=102.397. Step 8: 102.397-3.768=98.629. Step 9: 98.629-9.462=89.167. Step 10: 4.123+89.167=93.29 (Lean Body Weight: Fat Free Weight). Step 11: ((125-93.29) x 100) divided by 125 = (31.37 x 100) divided by 125 = 3171 divided by 125= 25.368 (Body Fat Percentage).

Note:The formulas above are just approximations.

The above information is from,
M&F magazine issue October 2007.
http://www.fitnessguidelines.com
http://www.myfittribe.com/articles/20081022/protein-guidelines.html
http://www.fitnessguidelines.com/articles/how-much-protein-should-i-take.html
http://www.davedraper.com/bodyfat-calculation.html