30 Questions
What is the structure of the plasma membrane?
Consists of two layers of phospholipids with embedded proteins and sugars
What is the function of the plasma membrane?
Control passage of substances into and out of the cell, regulating the intracellular environment
What are the components of the plasma membrane?
Phospholipids, proteins, sugars, and cholesterol
How are the phospholipid molecules arranged in the plasma membrane?
Arranged like a sandwich with the hydrophilic heads on the outer surfaces and the hydrophobic tails forming a central water-repelling layer
What role do membrane proteins play in the plasma membrane?
Provide channels for the passage of substances and electrolytes
What is the function of cholesterol in the plasma membrane?
Present in the membrane
What is the function of membrane proteins with branched carbohydrate molecules attached to the outside of the cell?
They give the cell its immunological identity - 'self' markers.
What are some functions of membrane proteins?
Act as receptors for hormones and other chemical messengers, and some are enzymes.
What is the property of the plasma membrane that allows it to control the entry or exit of substances?
Selective permeability.
How do lipid-soluble materials cross the membrane?
By dissolving in the lipid part of the membrane.
What is the process used by substances that are unable to diffuse through the semipermeable membrane unaided?
Facilitated diffusion.
What is osmosis?
Passive movement of water down its concentration gradient towards equilibrium across a semipermeable membrane.
What is active transport?
The transport of substances up their concentration gradient using chemical energy in the form of ATP.
What is the function of the sodium-potassium pump?
It maintains the unequal concentrations of sodium and potassium ions on either side of the plasma membrane.
How are particles too large to cross cell membranes transferred?
By pinocytosis ('cell-drinking') or phagocytosis ('cell-eating').
What is the term for the process of extrusion of waste material through the plasma membrane?
Exocytosis.
What are organelles?
Individual and highly specialised structures enclosed by their own membrane within the cytosol.
Which cells contain several nuclei?
Skeletal muscle fibres and some other cells.
What is the name of the fine network of threads that DNA is present as in a non-dividing cell?
Chromatin
What is the function of the nucleus?
Directs all metabolic activities and contains genetic material in the form of DNA.
What is the role of the nucleolus within the nucleus?
Involved in synthesis and assembly of the components of ribosomes.
What is the main function of mitochondria?
Central to aerobic respiration and the production of ATP.
What are ribosomes composed of?
RNA and protein
What is the role of smooth endoplasmic reticulum?
Synthesises lipids and steroid hormones, and is associated with the detoxification of some drugs.
What is the site of synthesis of proteins in a cell?
Rough endoplasmic reticulum and ribosomes
Where do the proteins move from the endoplasmic reticulum to be 'packaged' into membrane-bound vesicles?
Golgi apparatus
What is the main function of lysosomes?
Contain enzymes involved in breaking down fragments of organelles and large molecules inside the cell into smaller particles.
What is the function of the nuclear envelope?
It contains the nucleus and has tiny pores through which some substances can pass between it and the cytoplasm.
What is the form of energy made available in the cell by mitochondria?
ATP
What is the main function of the Golgi apparatus?
To 'package' proteins into membrane-bound vesicles and move them to the plasma membrane for exocytosis.
Test your knowledge of cell physiology with this quiz covering topics such as rough endoplasmic reticulum, nuclear envelope, chromatin, and the structure and functions of cell membranes.
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