Biological molecules
What are 4 types of polysaccharides?
Starch – energy storage in plants.
Glycogen – energy storage in animals (in liver & muscles).
Cellulose – makes up plant cell walls, gives structure.
Chitin – found in fungi cell walls & insect exoskeletons.
What are the 7 properties of water?
1. Polarity
2. Cohesion
3. Adhesion
4. Capillary action
5. Temperature control
(a.) High specific heat
(b. )Evaporative cooling
6. Floating ice
7. Solvent
Pathway of protein produced [6]
Rough ER=> vesicles => Golgi => vesicles=> plasma membrane
Describe "fluid mosaic" model of plasma membrane. What might shown on it?
plasma membrane is a flexible layer of phospholipids with proteins floating
Phospholipid bilayer (hydrophobic tails + hydrophilic heads)
• Channel and carrier proteins
• Cholesterol (for stability)
• Glycoproteins and glycolipids (for cell recognition)
What is central dogma?
DNA → RNA → Protein
Transcription: DNA makes RNA.
Translation: RNA makes proteins.
what are biological molecules represent short-term and long-term energy storage?
Short-term energy: Carbohydrates → glucose, glycogen, starch. Quick to break down for energy.
Long-term energy: Lipids → fats, oils. Store way more energy, slower to use.
Why water can control temperature? Why does it matters?
Hydrogen bonds.
Moderates air temperature
Stabilizes ocean temp
What are three types of active transport?
Sodium-potassium pump
Endocytosis (cell takes stuff in)
Exocytosis (cell releases stuff out)
What is the job of cilia?
Helps cell move
True or False: isontonic solution have net movement of water
NOOOOO！
What are 5/6 functions of protein?
Structural – build stuff (like collagen, keratin). Enzymatic – speed up reactions
Transport – carry molecules (hemoglobin moves oxygen).
Defense – antibodies fight infections.
Regulatory – hormones like insulin control processes.
Storage – store stuff like iron.
Why plants won’t burst in hypotonic solution?
the cell swells, but the cell wall’s pressure (turgor pressure) stops it from bursting.
What is the role of cholesterol?
Cholesterol is a lipid molecule in cell membranes that stabilizes membrane fluidity, making the membrane less permeable to very small water-soluble molecules and preventing it from becoming too rigid or too fluid.
What is the difference between integral protein and peripheral protein?(Membrane protein)
1.Integral proteins：Proteins that are embedded into the lipid
2. Peripheral proteins：Proteins that are not embedded into the lipid bilayer
What is Optimum Temperature?
The temperature at which an enzyme or biological process functions at its highest rate.
Give an example of hydration and dehydration
Sucrose adds H2O yielding glucose and fructose.
triglycerides adds H2O yielding glycerol + fatty acids.
Explain High heat capacity
Water’s high heat capacity means it can absorb or release lots of heat without changing temperature much .
Examples:
Oceans keep coastal climates stable
Your body stays cool because water in cells resists rapid temp changes
What is phagocytosis? What’s the path?
when a cell engulfs particles to be later digested by lysosomes.
Packaging into food vacuole——fuses with lysosomes —— digested
Describe "fluid mosaic" model of plasma membrane. What might shown on it?
The fluid mosaic model says the plasma membrane is flexible, like a liquid, with proteins and other molecules floating in it. You’d see phospholipid bilayer, embedded proteins, cholesterol, and carbohydrate chains.
How does the presence of double membranes and circular DNA in mitochondria and chloroplasts provide molecular evidence for the endosymbiotic theory？
The double membranes suggest that mitochondria and chloroplasts were once independent prokaryotes engulfed by a larger cell — the inner membrane from the original bacterium, the outer from the host. Their circular DNA resembles bacterial genomes, supporting that origin.
How the Protein structure change in different levels? what are two types of structure in the secondary level?
Primary: the linear sequence of amino acids in the polypeptide chain.
Secondary: folds due to hydrogen bonding within the polypeptide backbone.
Tertiary: 3D folding, formed by interactions between R groups (like hydrophobic interactions, ionic bonds, and disulfide bridges).
Quaternary:when multiple polypeptide chains associated.
All four stages determine the function of the protein
Use plants to explain water’s properties (adhesion, cohesion and capillary action )
Cohesion: water molecules stick to each other by hydrogen bonds, forming a continuous column.
Adhesion: water sticks to the walls of the xylem, helping it climb against gravity.
Capillary action: Occurs when adhesion is greater than cohesion, the water moves upward, important for transporting water and nutrients.
What is Carrier Protein and what does it do?
A membrane protein; Functions: binds to specific molecules and changes shape to transport them across the membrane. Some carrier proteins facilitate passive transport.
Why do smaller cells have a higher surface area to volume ratio, and how does this affect the rate of diffusion of materials in and out of the cell?
Smaller cells have a larger SA/V ratio, so there’s more surface area for each unit of volume. That means materials like oxygen and nutrients diffuse faster and more efficiently in and out. Big cells have a lower ratio, so diffusion is slower — that’s why cells stay small .
What are some impacts if people change of amino acid?
A different amino acid may change the protein’s shape, stability, or ability to interact with other molecules. This can lead to loss of function, reduced efficiency, or even disease.