Cell revision Flashcards
Cells are dynamic. Certain forms of movement require energy. Identify the one that does NOT.
facilitated transport.
Transport up electrochemical gradient does require energy.
Which option best represents the mean thickness of the phospholipid membrane bilayer?
8nm
All animal cells:
require a supply of energy.
About the other options: Animal cells do not have a cell wall; plant cells do. Most animal cells contain mitochondria, but some cells, such as red blood cells, do not. Cells that lack mitochondria cannot reproduce and cannot carry out extensive metabolic activities. The skeletal muscle fibre is an example of a cell type that contains many nuclei; at the other extreme red blood cells do not contain even one nucleus. Most cells have an asymmetrical shape: a motor neuron is a good example. Can you think of others?
What type of cell is the arrow is pointing to?
Goblet cells are modified columnar epithelial cells that secrete mucus. Before mucus is released, it accumulates in the upper portion of the cell causing it to bulge out making the whole cell resemble a goblet or wine glass.
Identify the correctly labelled portion of the molecule of phosphatidylcholine.
Phosphatidylcholine is an amphiphilic phospholipid molecule with polar glycerol molecule bonded to 2 non-polar fatty acid tails and phosphate. Phosphate is in turn bonded to a polar choline head.
A - hydrophilic choline head
Some membrane proteins have relatively low mobility within the membrane. According to modern models of membrane structure, this low mobility is due to protein interaction with
the membrane skeleton
The membrane skeleton acts like a series of actin-containing ‘fences’. These structures limit the movement of some proteins. Proteins may also be anchored to them.
Which option lists membranes in order of increasing percentage lipid content?
Lipid content of membranes ranges from 25% in the inner mitochondrial membrane, 50% in plasma membranes to around 80% in myelin sheaths. The other large component of membranes is protein.
inner mitochondrial membrane < plasma membrane < myelin sheath
Identify the correct directions of net movement of K+ and Na+ through open channels in the membrane of a resting cell:
Na+ inward, K+ outward
The Na-K ATPase
is driven by phosphorylation of an aspartyl residue
The Na-K ATPase maintains the osmotic balance by exporting Na+. The aspartyl residue is phosphorylated by ATP, not GTP. The Na-K ATPase is an antiporter: Na+ and K+ move in opposite directions.
The values 0.35-0.54 represent the normal boundaries (of both males and females) of which red cell parameter?
haematocrit
Haematocrit (packed cell volume) is the volume of blood occupied by red blood cells. It is expressed as a fraction of the total blood volume. The normal range is 0.35 to 0.54.
Which of the above has a diameter of 2-3μm?
Platelets are small blood cell fragments derived from megakaryocytes.
Features of platelets
Which of the above contains many organelles but no nucleus?
Platelets are small (2-3 μm), disc-shaped anuclear (without nucleus) cells that are involved in haemostasis. They have a life span of about 8 to 10 days. They are formed from fragments of cytoplasm shed from megakaryocytes in the bone marrow in a process called Thrombopoiesis.
