Recall Questions Flashcards
Using your knowledge of cell ultrastructure, identify the structures visible in the micrograph below. State with reasons, whether the cell is a plant or animal cell.
- Cell wall (1)
- chloroplast (1)
- plant cell (1)
- presence of, chloroplast/cell wall.
Many different organisms have cell walls including fungi and bacteria. What is unique about plant cell walls?
A plant cell walls contain cellulose.
Describe the similarities and differences between an human cell and plant root cell.
- Both have three named organelles (e.g. nucleus, cell surface membrane, mitochondria, ribosomes, Golgi body, endoplasmic reticulum)
- only plants have two named organelles (e.g. chloroplasts, cell wall, large (central) vacuoles)
- centrioles present in animal cells but not flowering plants (1).
What is a lysosome and why is the membrane that surrounds it so important?
- Lysosomes are specialised vesicles that contain hydrolytic enzymes for breaking down waste material.
- The membrane that forms lysosomes has an important role in compartmentalising these enzymes away from cell structures that could be damaged by activity of the enzyme.
Explain why cells need to be compartmentalised, and describe three examples within an animal cell.
- Incompatible reactions
- catabolic and anabolic reactions require different conditions
- damage due to hydrolytic enzymes
Three named examples:
- e.g. nucleus, vesicle, lysosome, mitochondrion, Golgi body, endoplasmic reticulum, chloroplast
List 3 differences between eukaryotic and prokaryotic cells.
Prokaryotic = no membrane bound organelles, no nucleus, smaller ribosomes, murein cell wall.
What is a plasmid?
A loop of DNA not part of main chromosomal DNA e.g genes for antibiotic resistance. Not in all bacterial cells.
Why might bacterial cells have a slime capsule?
To give protection against the cells of the immune system.
What is found in the cytoplasm in prokaryotic cells?
No membrane bound organelles and has smaller ribosomes than in eukaryotic cells.
What is the flagellum?
A long hair like structure that rotates to make the prokaryotic cells move.
Not all prokaryotes have a flagellum and some have more than one.
What is circular DNA?
Long coiled up strand of DNA that is not attached to any histone proteins.
Read the information in the table and for each object, state the type of microscope it could be resolved by.
1. E. coli bacterium - 2.0 um
2. Nuclear pore - 0.05 um
3. Human egg cell - 100 um
4. DNA helix - 0.002 um
5. Mitochondrion - 0.7 um
6. Influenza virus - 0.1 um
- Light, SEM, TEM
- SEM and TEM
- Light, SEM and TEM
- SEM and TEM
- Light, SEM and TEM
- SEM and TEM
Two teams of scientists are studying HIV. HIV has a diameter of 0.12μm. Team 1 are focused on HIV surface proteins and how they bind to immune system cells. Team 2 are studying the internal structure of the virus. Suggest what specific type of microscope each team might use during their studies. Explain your answer.
- Team 1: SEM – Need to use an electron microscope to ensure high resolution. SEM provides a 3D image of surface which is what Team 1 are focused on.
- Team 2: TEM – Would allow them to view the internal structure as thin slices of the specimen can be used and a higher maximum resolution than light microscope or SEM.
A team of researchers are investigating the function of a particular set of proteins within a tissue. In a thick sample of tissue they have tagged the different types of protein with fluorescent dyes so that they can identify them.
Suggest the type of microscope that the team could use to gain an understanding of what is happening at different depths of the sample.
Explain why your suggestion is suitable.
Laser scanning confocal microscope as it uses a laser beam that would cause the dyes to give off fluorescence to show where the different proteins are located. This microscope is also suitable for thicker samples as images can be taken at different depths within the tissue sample.
What kind of radiation are used in electron microscopes?
X-rays
Describe why you would use a TEM
To study thin specimens through which electrons can generate a projected image.
Why is a stain used when preparing a slide?
To enhance visualisation of the cell, or certain cellular components under a microscope.
Why does the specimen need to be thin when preparing a slide?
In order for light coming from the light source to pass up through so that they can be viewed
What is the maximum resolution power of TEM?
0.050 mm
2 advantages of using a TEM.
- powerful microscopes
- high magnification solution
3 disadvantages of the TEM
- Limited sampling
- Complex image interpretation
- Possibility of electron beam damage
In what 2 ways is the SEM better than the TEM?
- costs less
- take less time to produce an image
which type of microscope would be used to study replication of E.coli bacteria?
- Light
- SEM
- TEM
List the 3 main stages involved in cell fractionation.
- homogenising
- filtration
- centrifuging
What is the heaviest organelle?
nucleus
what are the lightest organelles?
ribosomes
Why does the solution have to be cold?
- To prevent unwanted chemical reactions by enzymes.
Why does the solution have to be isotonic?
So that the cell doesn’t burst due to water being inside it.
What is cell homogenisation?
The act of breaking the tissue to release organelles
Why must homogenate be filtered?
To remove large debris.
What are the first three steps at the start of centrifugation?
- The homogenate is spun in a centrifuge
2.Organelles fall to the bottom (order depending on density) forming a pellet
3.The supernatant is removed and spun at a higher speed
Explain why an ice-cold, isotonic, buffered solution is used in cell fractionation.
- Ice- cold: slow enzyme activity
- Isotonic: prevent damage to organelles
- Buffered: control pH
What are the inner folds of mitochondria called?
Cristae
What is the function of the Golgi apparatus?
To process and package new proteins and lipids.
It makes lysosomes.
What is the function of a lysosome?
Contains enzymes - lysozymes used to digest broken/invaded cells.
What is the function of a ribosome?
Protein synthesis
Describe the difference between smooth and rough endoplasmic reticulum.
Smooth = no ribosomes
What is the function of the smooth ER?
Synthesises and processes lipids.
What makes up the cell wall of plants and algae?
Cellulose
Why would an epithelial cell in the small intestine need lots of mitochondria?
Respiration, to give energy needed for absorption of nutrients.
Describe the function of the nucleolus.
Makes ribosomes.
What is the function of the nucleus?
Controls the cells activities by controlling the transcription of DNA. Has nuclear pores to allow substances to move between the nucleus and cytoplasm.
What is the function of the lysosome?
Contains digestive enzymes which are used to digest invading cells or break down worn components of the cell.
What is the function of the RER?
Folds and processes proteins that have been made at the ribosomes.
What is the function of the SER?
Synthesises and processes lipids
What is the function of the mitochondria?
Site of aerobic respiration, where ATP is produced. Found in large numbers in cells that are very active and require a lot of energy.
What is the function of the centriole?
Involved with the separation of chromosomes during cell division.
What are the 2 methods of cell division?
Mitosis and Meiosis
What is created through mitosis?
2 daughter cells
What is created through meiosis?
4 daughter cells.
What type of cells undergo mitosis?
All eukaryotes
Describe 3 uses of mitosis by organisms?
- Growth
- Repairing tissues
- Asexual reproduction
List the 3 stages of the cell cycle.
- Interphase - G1, S, G2
- Mitosis
- Cytokinesis
What is interphase?
The longest phase of the cell cycle in which the cell increases in size and makes a copy of its DNA.
What happens to a cell in interphase?
DNA unravels and replicates.
What is mitosis?
The type of nuclear division in which the daughter cells have the same number of chromosomes as the parent cell.
What is cytokinesis?
The process in which the cytoplasm of a single eukaryotic cell is divided to form two daughter cells.
List the stages of mitosis in order.
- Prophase
- Metaphase
- Anaphase
- Telophase
What is a centromere?
The point or region on a chromosome to which the spindle attaches during mitosis and meiosis.
What is a centriole?
An organelle inside animal cells that are made of microtubules and are involved in cilia, flagella and cell division.
Describe what occurs in prophase.
Chromosomes condense, the nuclear envelope breaks down and the mitotic spindle begins to form.
List 2 events that happen in metaphase
- Chromosomal alignment
- Spindle fibre attachment
Describe what cells would look like when undergoing anaphase.
Sister chromatids separate and move toward opposite poles of the cell.
List 2 events that happen in telophase.
- Chromatids decondense
- Nuclear envelope reformation
If 10 cells out of a total 100 are in metaphase & one complete cycle takes 15 hours, how long do cells spend in metaphase? Give your answer in minutes.
- Proportion of cells in metaphase:
10/100 = 0.1 - Conversion of cell cycle time to unit
15 hours - converted to minutes
15 x 60 = 900 - Calculate the proportion of time spent in metaphase.
0.1 x 900 = 90 minutes
Final answer: 90 minutes
Briefly, what causes cancer?
Cancer is generally caused by genetic mutations that lead to uncontrolled cell growth and division.
How are tumours linked to cell division?
They result from the abnormal regulation of the cell cycle, which includes the process of cell division.
What are the names given to the different types of tumour?
- Malignant
- Benign
What is the basic difference between a benign and malignant tumour?
Benign tumours are non cancerous, whereas malignant tumours are cancerous.
Why do cells replicate by mitosis?
- Growth and development
- Tissue repair and maintenance
- Asexual Reproduction
What affects rate of cell division?
Cell type, cellular environment, cell cycle regulators
What happens if the genes controlling cell division are damaged?
- Loss of cell cycle regulation
- Formation of tumours
If uncontrolled mitosis due to mutation occurs, how does this affect the cells being created?
- Rapid cell proliferation
- Loss of differentiation
- Genetic instability
- Tumour formation
