Cells Flashcards
Which of the following is the correct sequence of the four phases of mitosis?
Prophase, metaphase, anaphase, telophase
How did Pasteur’s experiment with sterile broth in open flasks demonstrate the principle
that cells only come from pre-existing cells?
By demonstrating that sterile broth would not ferment in contact with air alone.
Emergent properties are found in some biological systems. Which of the following
properties is necessary for emergent properties to occur?
Cells or tissues interact to function as a unit
Which of the following organelles are surrounded by a single membrane?
Rough endoplasmic reticulum
Lysosome
Which of the following are properties of cholesterol found in plasma membranes?
Reduces permeability of the membrane to hydrophilic ions
It is amphipathic
Reduces fluidity of the membrane
Which of the following are properties of phospholipids?
I They have a hydrophilic phosphate head
II They form a bilayer in water
III They are amphipathic
IV They have a hydrophobic fatty acid region
The medium in which a donor organ for transplant is bathed in an isotonic medium, a
solution of the same concentration as the cell cytoplasm. Why?
The organ must not lose or gain water
Which of the following can cause the formation of a primary tumour, or cancer?
I Oncogenes
II Mutagens
Which of the following events happens during mitosis in a plant cell?
Condensation of chromosomes (Occurs by supercoiling in prophase).
Which statement best describes the movement of water molecules in osmosis?
From a dilute to a more concentrated solution across a membrane
Outline how the mitotic index can be used in the diagnosis of cancer?
Mitotic index is a measure for how fast the cells are dividing (also known as proliferation) A high mitotic index means that the cells might be cancerous;
Mitotic Index is defined as the ratio between the number of cells actively dividing (in mitosis) and the total number of cells / a low mitotic index means that the cells are dividing slowly.
Mitotic index has been shown to be a strong predictor of / to correlate to survival / prognosis / treatment success in (some) cancers.
List two sources of stem cells that can be used in therapeutic treatment.
• The patient’s own cells / tissues / donated tissues from another person;
• The foetal umbilical cord (blood);
• Early-stage embryos (specially created);
- Outline two similarities between the structure of prokaryote cells and eukaryote cells.
Both cells have;
• plasma membrane
• ribosomes (although they are 70s in prokaryotes and 80s in eukaryotes)
• both cells contain DNA
Outline two similarities between the structure of prokaryote cells and eukaryote cells.
• plasma membrane
• ribosomes (although they are 70s in prokaryotes and 80s in eukaryotes)
• both cells contain DNA
Outline the role of cyclins in living cells
• Cyclins control different stages of the cell cycle;
• Concentrations of each cyclin rise and fall in each stage;
• The rise and fall of the concentrations activates proteins;
• The activated proteins carry out reactions specific to the stage of the cell cycle / allow the cell cycle to continue;
Describe one type of cell which is atypical to the concept of cell theory.
• Striated muscle – many nuclei along the length of a single cell/muscle fibre
• Giant algae – Large organisms containing only one nucleus
• Hyphal aseptate fungi – hyphae are not divided into cells and contain many nuclei in a single hypha
• Or equivalent example
The Davson-Danielli model of the membrane structure proposed a
layer of protein on the outside edges of membranes. Biological
evidence caused them to refine their model and later the SingerNicholson model became accepted as a better model of
membrane structure.
Describe one piece of evidence that falsified the Davson-Danielli
model in support of the Singer-Nicholson model (3 marks)
(Hubbell and McConnell 1968 improved methods of) freeze-etching to reveal details of the structure of membranes.
Freeze etching experiments strongly suggest that protein is found deeply embedded in the membrane;
A frozen membrane is fractured and splits along the interior hydrophobic part of the membrane;
A smooth matrix/layer is seen interrupted by particles/proteins is seen;
Allow marks for the following explanations - even if freeze etching is not mentioned;
There was evidence that proteins were present in the middle of the bilayer;
This proved that the Danielli Daveson model couldn’t be correct as this model has no protein in the middle of the lipid bilayer;
Define the term “cell differentiation”
Cell differentiation is the process by which a cell changes from one cell type (an undifferentiated cell / a stem cell) to another cell type / specialised cell (by expressing some of its genes and not others)
Explain the evidence which supports the endosymbiotic theory of the evolution of the
eukaryotic cell
• Mitochondria and chloroplasts are believed to have been free living (they are endosymbionts);
• Mitochondira and Chrloroplasts have double membrane which is evidence for endocytosis of the organelle;
• they have 70s ribosomes which are found in Prokaryotes;
• they have a DNA loop/naked DNA as found in Prokaryotes;
• they are self replicating which is evidence for them having been free living origin;
- Eukaryotic cells contain organelles which each have specific functions. Complete the table below, to identify the missing organelle names and the missing functions.
Organelle Structure Function
Nucleus Large structure surrounded by a double membrane with DNA and proteins inside. Contains the cell’s DNAand is the site of DNA replication
Golgi apparatus A stack of four or more flattened membrane disks Processes and packages proteins into vesicles
Lysosome A round organelle with a single membrane containing digestive enzymes. Digestion of molecular debris inside the cell.
Mitochondrion An organelle with a double membrane. The outer membrane makes the shape of the organelle but the inner membrane folds into cristae Carries out the reactions of the Krebs cycle / aerobic respiration
Which statement provides evidence for endosymbiosis?
Eukaryotic mitochondria and chloroplasts have their own circular DNA.
Which of the following are features of prokaryotes and eukaryotes?
-70s ribosomes: prokaryotes
-80s ribosomes: eukaryotes
-Naked DNA: prokaryote
DNA associated with proteins: eukaryote
What route is used to export proteins from the cell?
Rough endoplasmic reticulum - Golgi apparatus - Plasma membrane
Which organisms has DNA located in three organelles?
A fern
Which of the following will contribute to the cell theory?
- Living organisms are composed of cells.
- All cells come from pre-existing cells by mitosis.
- Cells are the smallest units of life.
Which process is possible due to the fluidity of cell membranes?
Endocytosis
Which organelle is involved in generating vesicles destined for the cell membrane?
Golgi apparatus
Which organelle is involved in generating vesicles destined for the cell membrane?
Lysosome
Which sequence shows increasing relative size?
Membrane thickness - Virus - Bacterium
In which parts of the digestive system are most water and glucose absorbed?
Water: Large intestine
Glucose: Small intestine
Which organelle provides evidence that eukaryotic cells originated when prokaryotes engulfed small free-living prokaryotes?
Chloroplasts
What is the principal mode of division for the prokaryote Escherichia coli?
Binary Fission
What stage does chromosome supercoiling occur?
Prophase
What stage does the sister chromatids migrate to opposite poles?
Anaphase
