CSCC SU18 ACTUAL TEST PAPER 2026
QUESTIONS AND SOLUTIONS GRADED A+
●● Components of a homeostatic mechanism.
Answer: - Control center: usually found in the hypothalamus of the
brain, contains the "set point" for the variable, receives info from the
receptors and sends instructions to effectors
- Receptors: detect or sense the variable and send that info to the control
center
- Effectors: receive instructions from the control center and carry them
out to get the variable back to normal
●● Examples of homeostatic mechanisms.
Answer: - The maintenance of body temperature
- Blood glucose levels
- Blood sodium levels
- Blood pressure
●● Negative feedback.
Answer: - When a change in the variable occurs, the body responds by
causing a change in the opposite direction
- The main way that homeostatic mechanisms work
,●● Positive feedback.
Answer: - When a change in the variable occurs, the body responds by
causing more of a change in the same direction
- Rarely used in the body
- Examples: blood clotting, oxytocin release during child birth, and milk
release
●● Structure of the plasma membrane.
Answer: - Semi-permeable, phospholipid bilayer
- Regulates passage of substances into and out of the cell
- Principal components: lipids, proteins, carbohydrates
●● Phospholipids in the plasma membrane.
Answer: - Hydrophilic head
- Hydrophobic tail
- Arranged in a double layer (bilayer) with the heads surrounded by fluid
and the tails kept from the water
●● Cholesterol in the cell membrane.
Answer: - Hydrophobic so found in the tail
- Maintains the consistency of the cell membrane
- Strengthens it by preventing smell molecules from crossing
,- Keeps the phospholipid tails from coming into contact and solidifying
it to ensure the hydrophobic tail stays fluid and flexible
●● Proteins in the cell membrane.
Answer: - Function as enzymes to speed up chemical reactions
- Act as receptors for specific molecules or transport materials across the
cell membrane
- Integral proteins are located within the lipid bilater
- Peripheral proteins are located outside the lipid bilayer
●● Carbohydrates in the cell membrane.
Answer: - Sometime attached to proteins or lipids on the outside of the
cell membrane
- Form the glycocalyx which provides cushioning and protection for the
membrane, important for cell recognition and determining if cells should
be there or not, and acts as a glue to attach cells together
●● Polar substances.
Answer: - Water soluble
- Water, sodium, potassium
●● Nonpolar substances.
Answer: - Fat soluble
, - Urea, carbon dioxide, oxygen, and alcohol
●● Solubility.
Answer: - Like dissolves like
- Polar liquids dissolve polar substances
- Nonpolar liquids dissolve nonpolar substances
●● What substances can easily pass through the phospholipid bilayer of
cell membranes?.
Answer: - Nonpolar substances will pass through easily
- Polar substances must go through a channel in the cell membrane
●● Disorder.
Answer: - Disorder increases
- Molecules want to go where there is more room for them to spread out
●● Diffusion.
Answer: - The movement of small molecules from an area of high
concentration to an area of low concentration
- Does not require ATP energy
- Consists of a solute (molecules being dissolved) and a solution (water)
- Nonpolar, small lipid-soluble molecules will easily pass through the
lipid bilayer
QUESTIONS AND SOLUTIONS GRADED A+
●● Components of a homeostatic mechanism.
Answer: - Control center: usually found in the hypothalamus of the
brain, contains the "set point" for the variable, receives info from the
receptors and sends instructions to effectors
- Receptors: detect or sense the variable and send that info to the control
center
- Effectors: receive instructions from the control center and carry them
out to get the variable back to normal
●● Examples of homeostatic mechanisms.
Answer: - The maintenance of body temperature
- Blood glucose levels
- Blood sodium levels
- Blood pressure
●● Negative feedback.
Answer: - When a change in the variable occurs, the body responds by
causing a change in the opposite direction
- The main way that homeostatic mechanisms work
,●● Positive feedback.
Answer: - When a change in the variable occurs, the body responds by
causing more of a change in the same direction
- Rarely used in the body
- Examples: blood clotting, oxytocin release during child birth, and milk
release
●● Structure of the plasma membrane.
Answer: - Semi-permeable, phospholipid bilayer
- Regulates passage of substances into and out of the cell
- Principal components: lipids, proteins, carbohydrates
●● Phospholipids in the plasma membrane.
Answer: - Hydrophilic head
- Hydrophobic tail
- Arranged in a double layer (bilayer) with the heads surrounded by fluid
and the tails kept from the water
●● Cholesterol in the cell membrane.
Answer: - Hydrophobic so found in the tail
- Maintains the consistency of the cell membrane
- Strengthens it by preventing smell molecules from crossing
,- Keeps the phospholipid tails from coming into contact and solidifying
it to ensure the hydrophobic tail stays fluid and flexible
●● Proteins in the cell membrane.
Answer: - Function as enzymes to speed up chemical reactions
- Act as receptors for specific molecules or transport materials across the
cell membrane
- Integral proteins are located within the lipid bilater
- Peripheral proteins are located outside the lipid bilayer
●● Carbohydrates in the cell membrane.
Answer: - Sometime attached to proteins or lipids on the outside of the
cell membrane
- Form the glycocalyx which provides cushioning and protection for the
membrane, important for cell recognition and determining if cells should
be there or not, and acts as a glue to attach cells together
●● Polar substances.
Answer: - Water soluble
- Water, sodium, potassium
●● Nonpolar substances.
Answer: - Fat soluble
, - Urea, carbon dioxide, oxygen, and alcohol
●● Solubility.
Answer: - Like dissolves like
- Polar liquids dissolve polar substances
- Nonpolar liquids dissolve nonpolar substances
●● What substances can easily pass through the phospholipid bilayer of
cell membranes?.
Answer: - Nonpolar substances will pass through easily
- Polar substances must go through a channel in the cell membrane
●● Disorder.
Answer: - Disorder increases
- Molecules want to go where there is more room for them to spread out
●● Diffusion.
Answer: - The movement of small molecules from an area of high
concentration to an area of low concentration
- Does not require ATP energy
- Consists of a solute (molecules being dissolved) and a solution (water)
- Nonpolar, small lipid-soluble molecules will easily pass through the
lipid bilayer
