Cells and Microscopy - Key Concepts Flashcards
What is the difference between prokaryotes and eukaryotes?
Eukaryotes are organisms made up of eukaryotic cells (these contain a nucleus).
Prokaryotes are single prokaryotic cells (these do not contain a nucleus).
Which sub-cellular structures are found in most animal cells?
- Nucleus
- Cell membrane
- Mitochondria
- Ribosomes
Which sub-cellular structures are found in most plant cells?
- Nucleus
- Cell membrane
- Cell wall
- Chloroplasts
- Mitochondria
- Vacuole
- Ribosomes
Which sub-cellular structures are found in most bacteria?
- Chromosomal DNA
- Plasmid DNA
- Cell membrane
- Ribosomes
What is the function of the cytoplasm?
It is a jelly-like material that contains dissolved nutrients and salts. It is where many of the cell’s chemical reactions occur.
What is the function of the nucleus?
It controls the cell’s activities. It contains the chromosomes, which carry the genetic material.
What is the function of the cell membrane?
It is a thin, partially-permeable (only lets certain substances in and out) boundary boundary around the cell’s cytoplasm.
What is the function of the mitochondria?
They are dispersed in the cytoplasm. They host aerobic respiration.
What is the function of the ribosomes?
They host all protein synthesis.
What is the function of the cell wall?
It is a fully-permeable outer layer (in plants made of cellulose) that strengthens the cell.
What is the function of chloroplasts?
They contain chlorophyll (a green pigment) which is used to absorb light energy in photosynthesis.
What is the function of the vacuole?
It contains cell sap - a liquid which acts as a reservoir of salts, dissolved sugars, mineral ions, etc. It helps to keep the cell rigid by expanding.
What is the function of chromosomal DNA?
It contains the bulk of a bacterium’s DNA, loose in the cytoplasm.
What is the function of plasmid DNA?
It is present in closed circles of DNA in the cytoplasm, which can move between bacteria.
What is the function of flagella?
They can rotate or move in a whip-like motion to move the bacterium.
How are sperm cells adapted to their specialised function?
The head contains the genetic material for fertilisation in a haploid nucleus. The acrosome in the head contains enzymes so that a sperm can penetrate an egg. The middle piece is packed with mitochondria to release energy needed to swim and fertilise the egg. The tail enables the sperm to swim.
How are egg cells adapted to their specialised function?
The cytoplasm contains nutrients for the growth of the early embryo. The haploid nucleus contains the genetic material for fertilisation. The cell membrane changes after fertilisation by a single sperm so that no more sperm can enter.
How are ciliated epithelial cells adapted to their function?
Cilia on the surface beat to move fluids and particles up the trachea.
Describe the use of the two main types of microscope.
Light microscopes are used to study living cells and for regular use when relatively low magnification and resolution is enough.
Electron microscopes provide higher magnifications and higher resolution images but cannot be used to view living cells.
How does one calculate the magnification of a light microscope?
Magnification of the microscope = magnification of eyepiece * magnification of objective
How does one calculate the magnification based on an image of an object?
Magnification = size of image / (real) size of object
What is the difference between the two main types of microscope?
Electron microscopes use a beam of electrons, while light microscopes use rays of visible light.
Why can electron microscopes not be used to observe living cells?
Electron microscope samples are placed in a vacuum.
Compare the two types of electron microscope.
The transmission electron microscope (TEM) is used to examine thin slices or sections of cells or tissues.
The scanning electron microscope (SEM) has a large depth of field so can be used to examine the surface structure of specimens.
The TEM has superior magnification and resolution.
