Exam Questions Flashcards
(29 cards)
Name and describe five ways substances can move across the cell-surface membrane into a cell.
1)Simple diffusion of small/nonpolar molecules down a concentration gradient.
2)Facilitated diffusion down a concentration gradient via carrier proteins and channel proteins.
3)Osmosis of water down a water potential gradient.
4)Active transport against a concentration gradient via carrier proteins using ATP.
5)Co-transport of 2 different substances using a carrier protein.
Describe and explain two features you would expect to find in a cell specialised for absorption.
1)Microvilli - provides a large surface area for absorption.
2)Large number of mitochondria - for aerobic respiration.
The movement of substances across cell membranes is affected by membrane structure. Describe how.
1)Phospholipid bilayer allows for the diffusion of non-polar substances.
2)Carrier proteins allow for active transport.
3)Channel proteins and carrier proteins allow for facilitated diffusion and co-transport.
4)The number of channel and carrier proteins determine how much movement occurs.
5)Cholesterol affects the permeability.
Give two similarities in the movement of substances by diffusion and by osmosis.
1)Both move down a gradient.
2)They are both passive processes.
Suggest and explain two ways the cell-surface membranes of the cells lining the uterus may be adapted to allow rapid transport of nutrients.
1)Large number of carrier proteins and channel proteins for facilitated diffusion.
2)Large number of carrier proteins for active transport.
Compare and contrast the processes by which water and inorganic ions enter cells.
1)Both move down a concentration gradient.
2)Both move through channel proteins in membranes.
3)Ions can move against a concentration gradient by active transport.
Contrast the processes of facilitated diffusion and active transport
1)Facilitated diffusion involves channel or carrier proteins whereas active transport only involves carrier proteins.
2)Facilitated diffusion doesn’t use ATP whereas active transport uses ATP.
3)Facilitated diffusion is down a concentration gradient whereas active transport is against a concentration gradient.
Describe how phospholipids are arranged in a plasma membrane
1)Bilayer.
2)Hydrophobic tails in the inside.
3)Hydrophilic heads on the outside.
Describe how the RER is involved in the production of enzymes.
1)It has ribosomes.
2)To make proteins - which an enzyme is.
Describe how the Golgi apparatus is involved in the secretion of enzymes.
Modifies proteins
Explain how water enters a bacterial cell.
1)Water potential is more negative.
2)Water enters by osmosis.
Describe how substances move across cell-surface membranes by facilitated diffusion.
1)Carrier and channel proteins are complementary to the substance.
2)Substance moves down a concentration gradient.
Describe two functions of the phospholipid bilayer.
1)Able to form vesicles.
2)Allows non-polar molecules to pass through.
Give one function of a surface protein.
Cell recognition
Explain why different proteins are required for the diffusion of different ions through the membrane.
1)Each protein has a specific tertiary structure.
2)Because the ions have different shapes.
Explain why molecules of oxygen and carbon dioxide are able to diffuse across membranes.
1)Oxygen and carbon dioxide are small, non-polar molecules.
2)So oxygen and carbon dioxide can diffuse down a concentration gradient.
The structure of a plasma membrane is described as a fluid mosaic. Explain why
1)Fluid - molecules move around.
2)Mosaic - made up of different molecules
Give two functions of proteins in plasma membranes.
1)Cell recognition
2)Carriers
Explain how sodium ions are transported through the membranes.
1)Active transport
2)By specific carrier proteins.
Explain how three features of a plasma membrane adapt it for its functions.
1)Phospholipid bilayer, allows non-polar substances to pass.
3)Carrier proteins - allows active transport and facilitated diffusion.
Cholesterol - regulates fluidity
An optical microscope cannot be used to see a plasma membrane. Explain why.
1)It has a lower resolution.
2)Light has a longer wavelength
How does the phospholipid bilayer affect entry and exit of substances into and out of a cell?
1)Allows movement of non-polar molecules.
2)Prevents movement of polar molecules.
3)It is partially permeable.
Describe the structure of a plasma membrane and explain how different substances are able to pass through the membrane by diffusion.
1)Phospholipids form the bilayer.
2)Made up of channel proteins, carrier proteins and surface proteins.
3)Made up of cholesterol which regulates fluidity.
4)Substances move down a concentration gradient.
5)Carrier proteins are involved with facilitated diffusion.
