Cell Membrane
What is the main function of the cell membrane?
To control what enters and exits the cell
Which type of transport moves substances from high to low concentration and does NOT require energy?
Passive transport
In which type of solution will water move into the cell, causing it to swell?
Hypotonic
What is the definition of homeostasis?
The process of maintaining internal balance
Why do your fingers wrinkle in water (cell behavior)?
Osmosis causes cells to lose water in hypotonic environment
What are the two parts of a phospholipid?
Hydrophilic head and hydrophobic tail
What is osmosis?
The diffusion of water through a selectively permeable membrane
What happens to a red blood cell in a hypertonic solution?
It shrinks
Which hormone helps regulate blood sugar levels?
Insulin
What happens to a houseplant that isn’t watered for a week?
Loses water via osmosis → low turgor pressure → wilts
What term means the membrane only allows some substances to pass?
Selectively permeable or semipermeable
Which type of passive transport uses protein channels to help move larger molecules?
Facilitated diffusion
What type of solution has equal concentrations of water inside and outside the cell?
Isotonic
Is shivering an example of positive or negative feedback?
Negative
A person eats a sugary meal. What hormone is released and what does it do?
Insulin; lowers blood sugar by moving glucose into cells
Name two components found in the membrane besides phospholipids.
Proteins, carbohydrates, cholesterol
What kind of transport moves materials from low to high concentration and uses ATP?
Active transport
Why do plant cells not burst in hypotonic solutions?
Their rigid cell wall prevents bursting
Which type of feedback loop increases the original signal?
Positive Feedback
A bumblebee shivers to warm its flight muscles. What type of loop is this?
Negative feedback loop
Why can small, nonpolar molecules like oxygen and carbon dioxide pass directly through the cell membrane, while large or charged molecules cannot?
Because the cell membrane is made of a nonpolar lipid bilayer, small nonpolar molecules can dissolve in and pass through it easily. Large or charged molecules cannot cross the hydrophobic core without help from transport proteins.
What are two types of active transport that use vesicles made from the membrane to transport large amounts of molecules?
Endocytosis and exocytosis
A cell has 90% water and is placed in a solution with 80% water. In which direction will water move?
Out of the cell
Give one example of a positive feedback loop and explain it.
Childbirth or blood clotting – the response increases the stimulus, moving away from homeostasis
After heavy exercise, why does your heart rate increase?
o deliver more oxygen and glucose for respiration → maintain homeostasis