Biology B1

• Carbohydrates give slow release energy
• Fats keep you warm as well as being used for energy in survival conditions
• Protein is used for growth; cell repair; and cell replacement
• fibre helps your digestive system run smoothly
• Vitamins and Minerals keep your skin, bones, and blood healthy

your metabolic rate is the rate at which the reactions in your body that keep you alive occur.

Muscle requires more energy that fat cells therefore people with a higher muscle to fat ratio will have a higher metabolic rate. The same goes for people who are physically larger as the bigger you are the more energy is required to keep you alive.

Your metabolic rate is also affected by your gender as well as your genetics

People with more physically demanding jobs also have a higher metabolic rate as they require more energy than someone with a less physically demanding job. For example a builder has a higher metabolic rate than someone who works in an office.

Diet- excess fat or carbohydrates lead to obesity as the energy they are producing is not being used up by your body therefore it is stored as fat cells.

MALNOURISHED PEOPLE CAN BE FAT OR THIN.

Obesity is defined as being 20% or more over the recommended body mass.

Causes-  Hormones, unbalanced diet, over eating, lack of excercise

Obesity can lead to several health problems such as: arthritis, type 2 diabetes, high blood pressure, heart disease as well as increasing the risk of cancer.

Saturated fats increase your blood cholestrol

A lack of exercise also leads to obesity. As energy is stored as fat first before being used up

Inheritance can also be a cause of obesity such as an underactive thyroid gland 

There are 2 main types of pathogen; Bacteria and viruses

Bacteria are very small living cells, they are roughly 1/100th of the size of our cells. They are able to rapidly reproduce inside of the body and they make you feel ill by either damaginf your cells or releasing toxins.

Viruses are not cells they are even smaller roughly 1/100th the size of a bacterium. They invade your cells and use the cells machinery to make copies of themselves. The cell will usually burst and it is the damage to your cells that amkes you feel ill.

The body has a pretty advanced defence system to try and prevent the invasion of pathogens.

Skin, hairs and mucus in your respiratory tract stop a lot of pathogens from invading that way, and to try and prevent microorganisms invading through the blood stream platelets help clot the blood quickly in order to seal off cuts.

When pathogens do invade the immune system takes control

White blood cells have 3 main ways of destroying microbes:

A) consuming them-

white blood cells can engulf foreign cells and digest them.

B) Producing antibodies:

Step one- every invading cell has unique molecules, called antigens on its surface
Step two- when a white blood cell comes across an antigen they dont recognise they begin to produce proteins called anti bodies to lock on to the invading cells and kill them. The antibodies produced are specific to that antigen and will be able to be produced quickly if the body is exposed to that antigen again. Step three- antibodies are then produced quickly and carried around the body tto kill all of that bacteria or virus.

C) Producing antitoxins-

these counteract the toxins produced by the bacteria which are infecting the cells

Hormones are chemical messengers sent by the blood

Hormones are carried throughout the body via the blood plasma but only affect certain cells known as target cells. The job of hormones is to control things in cells and organs that need constant adjustment.

The Pituitary Gland located beneath the brain produces FSH and LH both of which are linked to the menstrual cycle (card 6) And the Ovaries prodce oestrogen which is also involed in the menstrual cycle (card 6)

Hormones do a similar job to nerves however there are 3 major differences.

Speed- nerves act very quickly whereas hormones are slow in comparison

length of effect- nerves have a very fast short term effect however hormones react more slowly yet last for longer periods of time.

Area they affect- nerves target a specific area but hormones tend to work in a more general way.

FSH 

1) produced in the pituitary gland
2) causes the egg to mature in the ovaries
3) stimulates the ovaries to produce oestrogen

Oestrogen

1) produced in the ovaries
2) causes the pituitary gland to produce LH
3) stops any more FSH being released

LH

1) produced in the pituitary gland
2) stimulates the release of an egg at roughly the fourteenth day of the menstrual cycle