bio essay

Question 1

Important in cells and organelles

Answer 1

• cells: cell surface membrane allows protection and organisation of cells
• control movement of substances into and out of cells, have semi-permeable nature
• organelles: enclosed by plasma membranes. vital for control of entry and exit of materials

Question 2

Cell surface membranes- phospholipid bilayer

Answer 2

• hydrophobic barrier formed between inside and outside of cell. Repel water
• hydrophilic phosphate heads help to hold at the surface. Polar so repels other polar molecules
• small gaps between phospholipids so only small molecules can pass through bilayer
• important for allowing lipid-soluble, small, or non-polar substances to enter and leave cell
• prevent water soluble, polar, and large substances from entering and leaving cell

Question 3

Proteins- facilitated diffusion

Answer 3

• interspersed throughout cell surface membrane
• intrinsic proteins completely span the phospholipid bilayer from one side to the other. Either protein channels of carrier proteins
• only way large, polar, or water-soluble substances can pass through bilayer
• proteins channels- are water-filled tubes, permeable to specific water-soluble ions
• carrier proteins- bind to ions or molecules then change shape to move these molecules across the membrane
• vital for transport of glucose and amino acids
• passive process. No energy needed. Substances move down conc gradient

Question 4

photosynthesis

Answer 4

• chloroplasts are organelles that carry out photosynthesis
• chloroplast envelope. Double plasma membrane
• highly selective in what it allows to enter and leave the organelle
• Inside the chloroplasts, closed chlorophyll-containing membranes called thylakoids use light energy to split water, transport ions, and reduce NADP to NADPH.
• this is vital as the thylakoid membrane is the site of photosynthesis’ LDR

Question 5

respiration

Answer 5

• Mitochondria are the sites of aerobic stages of respiration
• double membrane that controls entry and exit of material
• inner membrane folded to form extensions called cristae
• cristae provide large SA for attachment of enzymes involved in respiration.
• Having more cristae gives the mitochondrion more locations for ATP production to occur. In fact, without them, the mitochondrion would not be able to keep up with the cell’s ATP needs

Question 6

Second messenger model

Answer 6

• adrenaline binds to transmembrane protein receptor within cell surface membrane of a liver cell
• binding causes the protein to change shape inside the membrane
• leads to activation of enzyme adenyl cyclase which converts ATP into cAMP
• cAMP acts as second messenger that binds to protein kinase enzyme, changing its shape and therefore activating it
• protein kinase catalyses the conversion of glycogen to glucose.
• important for the regulation of blood glucose conc