B2.1

Question 1

explain how substances are transported in and out of cells through diffusion

Answer 1

• diffusion is the net movement of particles from an area of high concentration to an area of low concentration
• it occurs in liquids and gasses because the particles are free to move around randomly
• only small molecules such as glucose, water and amino acids can diffuse through the cell membrane

Question 2

explain how substances are transported in and out of cells through osmosis

Answer 2

• osmosis is the net movement of particles from an area of higher water potential to lower water potencial through a semi permeable membrane
• a cell membrane is semi permeable because it has small holes in that only allowe smal molecules like water to pass though
• the water molecules actually passses boh direcction because water moves randomly
• but there is a steady net flow of water into the side with fewer water molecules eg the sucrose solution becomes more dilute

Question 3

explain what water potential is

Answer 3

• water potential is the likhood of water molecules to diffuse in or out of a solution
• if a substance has a high water potential then it has a high concentration of water molecules
• if a substance has a low water potential it has a low concentration of water molecules

Question 4

explain how substances are transported in and out of cells through active transport

Answer 4

• active transport is the movement of particles against concentration gradient from and area of lower concertation to higher concentration using atp released during respiration
• Sometimes dissolved molecules are at a higher concentration inside the cell than outside but are still needed for the organism
• Carrier proteins pick up specific molecules and take them through the cell membrane against the concentration gradient.

Question 5

describe the process of mitosis in growth

Answer 5

• cell begins to divide
• DNA replicates to form two of each chromosomes
• nuclear membrane breaks down
• chromosomes line up across the center of the cells
• one set of chromosomes pulled to each end of the cell
• nucleus divides
• cytoplasm and cell walls divide to create two identical daughter cells

Question 6

describe the cell cycle

Answer 6

• cell growth
• DNA synthesis
• and chromosomes double stranded
• mitosis
• cytoplasm splits two separate cells are formed
• cell resting period or cell stops dividing

Question 7

explain the importance of cell differentiation

Answer 7

• differentiation is the process by which a cell changes to become specialized
• its important for cells to be specialized as it allows the cell to be more efficient
• and carry out a specific function in the organism

Question 8

recall where stem cells are present in plants and animals

Answer 8

• in plants they are located in the meristem
• in animals they are present in embryos

Question 9

describe the functions of stem cells

Answer 9

• stem cells are undifferentiated and can divide by mitosis to become new cells which can differentiate

Question 10

describe the difference between embryonic and adult stem cells

Answer 10

• adult stem cells are only found in certain parts of the body for example bone marrow
• they are less versatile and can only form cells form the tissue they were originally found
• they are used to replace damaged cells like new skin or blood cells

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• embryonic stem cells are found in early human embryo’s
• they have the potential to turn into any kind of cell

Question 11

describe the function of meristems in plants

Answer 11

• plant stem cells divide by mitosis and are found in plant meristems
• meristem tissue is found in the shoots and roots of plants
• they produce unspecialized cells that are able to divide and form any type of plant cells for as long as the plant lives
• the unspecialized ells can become specialized and form tissues like xylem and phloem