Human Biology Semester 1 Exam

Question 1

what is cell membrane ?

Answer 1

• Also known as the plasma membrane
• Separates cells from each other
• Very thin
• Substances must pass through
• Determines what enters and leaves

Question 2

what are lipids and proteins ?

Answer 2

• Lipids attached to phosphate molecules = phospholipid
• Arranged into 2 layers – bilayer
• Heads on the outside ( attract water )
• Tails inside ( repel water )
• Proteins throughout bilayer which carry out function of membrane

Question 3

solutions example ( 3)

Answer 3

Solute- substance that dissolves into a solvent ( eg sugar )
Solvent – substances that a solute dissolve into ( eg water )
Solution- solute + solvent

Question 4

What is diffusion ?

Answer 4

• Movement of substances from a area of high concentration to low concentration through differentially permeable membrane
• If there is a high concentration outside the cell and a low concentration inside the cell then the substance will move into the cell
• Passive process ( doesn’t need energy )
• Diffusion gradient – difference in concentration that brings about the movement of particles from H-> L ( Down hill )
• The greater the difference in concentration the greater the diffusion gradient and the fast the movement of particles

Question 5

what is osmosis ?

Answer 5

• Special type of diffusion that involves water molecules
• Water molecules move from a region of high water concentration ( low solute concentration ) to low water concentration ( high solute concentration ) through differentially permeable

Question 6

Carrier- Mediated transport

Answer 6

• Special proteins in cell membrane
• Proteins bind to ion or molecule assisting movement across membrane
• Proteins are specific

Question 7

Facilitated Diffusion

Answer 7

• For molecules that are too large to fit across cell membrane by normal diffusion
• Passive process
• Molecule combines with protein
• Protein changes shape, move molecules to other side ( low concentration )

Question 8

Active Transport

Answer 8

• Movement of substances from a region of low concentration to high concentration
• Against the gradient
• Cell must use energy ( mitochondria )
• Substances is attached to a carrier molecule and carried over membrane
• Similar to facilitated diffusion

Question 9

Vesicular Transport

Answer 9

• Active process
• Material enclosed in vesicle
• Vesicle – bubble-like structure surrounded by a membrane

Question 10

Endocytosis + Exocytosis

Answer 10

Some substances can’t pass through the cell membrane
Endocytosis – taking substances into the cell via a vesicle
- Phagocytosis – cell eating
- Pinocytosis – cell drinking
Exocytosis – removing substances from the cell via vesicle

Question 11

Factors Affecting The Exchange of material:

Answer 11

For Nutrients to diffuse into a cell they must traverse the cell membrane. Cell membranes are extremely thin to allow for the diffusion of materials across the cell membrane.

Question 12

Factors affecting the exchange of material: temp and pressure

Answer 12

As with any chemical reaction, increasing the temperature or pressure increases the kinetic energy of the particles, thus increasing the rate of diffusion.

Question 13

Factors affect exhange of material: Concentration Gradient

Answer 13

The greater the concentration gradient (the difference in concentration either side of the membrane) the greater the rate of diffusion.

Question 14

factors effect exchange of material: Surface Area

Answer 14

The larger the area over which diffusion can occur, the greater the rate of diffusion.

• the various tissues of the human body perform specific functions and can be categorised into four basic tissue types: epithelial, connective, muscular and nervous

Question 15

factors that affect exchange of material: Tissue

Answer 15

• is a group of similar cells that work together to perform a common function

Question 16

factors that affect exchange of material: Metabolism

Answer 16

• All cells carry out chemical processes that keep the organism alive and all the chemical reactions that take place are referred to as metabolism

Question 17

what is catabolic metabolism ?

Answer 17

• is the reactions large molecules are broken down to smaller ones
• Digestion is an example of catabolism.
• Release energy

Question 18

what is anabolic metabolism ?

Answer 18

• is the reactions in which small molecules are built up into larger ones
• .Protein synthesis is an example of anabolism.
• Require energy

Question 19

what is metabolism ?

Answer 19

Metabolism is concerned with maintaining a balance between energy release and energy utilisation.

Question 20

what are nutrients

Answer 20

A nutrient is any substance in food that is used for growth, repair or maintaining the body; that is, any substance required for metabolism.
There are six groups of nutrients:
 Water
 Carbohydrates
 Lipids
 Proteins
 Minerals
 Vitamins.

Question 21

organic compounds:

Answer 21

• molecules that have a carbon chain
• contain a number of hydrogen atoms and can include atoms of oxygen, nitrogen and sulphur.

Question 22

carbohydrates

Answer 22

• the main source of energy for cells.
• Simple sugars (monosaccharides), particularly glucose, are used in cellular respiration to release energy.

Question 23

complex carbohydrates

Answer 23

• such as starch, are broken down to simple sugars.
• contain atoms of carbon, hydrogen and oxygen.

Question 24

simple sugars

Answer 24

Simple sugars
- join together to form larger molecules (disaccharides).
Polysaccharides
- larger carbohydrate molecules formed when many simple sugars join together.

Question 25

lipids

Answer 25

Lipids
- fats and oil and are another important energy source.
- broken down to fatty acids and glycerol.
- Glycerol is broken down to release energy in a similar way to glucose.
- Each lipid molecule consists of one molecule of glycerol and one, two or three fatty acid molecules.

Question 26

proteins

Answer 26

Proteins
- made up of many amino acids. The most import
- An amino acid is a molecule that contains an amino group and a carboxylic acid group.
When two amino acids bond together, these two groups react to form a peptide bond, releasing a water molecule. There are 20 different amino acids found in proteins, proteins, each one differing in the structure of the side chain.

Proteins consist of 100 or more amino acids; their type and order are determined by the DNA that codes for the protein’s production. Each protein has a characteristic shape due to the folding of the chain.

• Shorter lengths of amino acids include dipeptides and polypeptides.
• Other organic compounds include nucleic acids such as ribonucleic acid (RNA) and deoxyribonucleic acid (DNA).

Question 27

inorganic compounds

Answer 27

• not based on a carbon chain.
• Most do not contain carbon atoms, but those that do, such as carbon dioxide, are small molecules.

Question 28

water

Answer 28

• Is important because it is the fluid in which other substances are dissolved.
• Some of the cell’s chemical reactions occur in water, and in others water molecules actually take part in the reaction.

Question 29

minerals

Answer 29

• Is important because they may be a part of enzymes, function as cofactors for enzymes, or be a part of substances such as adenosine triphosphate (ATP) that are involved in metabolism.

Question 30

vitamins

Answer 30

• act as coenzymes for many of the chemical reactions of metabolism.

Question 31

what is enzymes ?

Answer 31

• biological catalysts that are able to speed up chemical reactions by lowering the activation energy. They are not consumed or altered in the reaction.

Question 32

losteps of enzymes

Answer 32

1. The molecule on which an enzyme acts is called the substrate. Each enzyme will combine with only one particular substrate so is involved in only one specific reaction.
2. The enzyme and its substrate have characteristics that are complementary to one another; they have a shape and a structure that allow them to fit together.
3. The part of the enzyme molecule that combines with the substrate is called the active site. When the enzyme and substrate are combined, they are called an enzyme–substrate complex.

Question 33

lock and key model

Answer 33

1 Lock-and-key model
States that shape of the enzyme (the key) is always complementary to the shape of the substrate (the lock). Therefore, the two will fit exactly to form the enzyme–substrate complex

Question 34

induced-fit model

Answer 34

States that when the enzyme and substrate join, they form weak bonds that cause the shape of the enzyme to change, creating complementary shapes.

Question 35

factors affecting enzymes activity: the higher the concentration

Answer 35

• The higher the concentration of enzyme, the faster the rate of a chemical reaction because there are more enzyme molecules to influence reactants. By regulating the type and number of enzymes present, the body is able to control which reactions occur and the rate at which they proceed.