Introduction to Cell Biology – Structure and Function of the Cell Flashcards
What are the three principles of cell theory?
- Cells are the fundamental units of life
- All organisms are composed of cells:
- All cells come from pre-existing cells:
Describe the principle Cells are the fundamental units of life:
The principles that underlie the functions of the single celled bacterium are similar to those governing the 60 trillion cells of your body.
Describe the principle All organisms are composed of cells
Life is continuous, arising from other cells.
Describe the principle All cells come from pre-existing cells.
The origin of life on Earth was marked by the origin of the first cells.
Prokaryotic cells include…
…all bacteria and possess a simpler structure than eukaryotic cells.
What are prokaryotic cells?
Cells with no defined nucleus
What is the function of the plasma membrane in prokaryotes?
separates the external environment from the internal cytoplasm. It creates an impermeable barrier to most molecules.
What is the function of the cell wall in prokaryotes?
Cell wall provides strength and rigidity: but permeable to many small molecules
Eukaryotic cells include…
…all plants and animals as well as many single celled organisms: algae, amoebae, fungi and moulds. (Eukaryotic – cells with a true nucleus)
Unlike prokaryotes, eukaryotic cells contain…
…extensive internal membranes that define a collection of subcellular structures – organelles
The cytoplasm of eukaryotes also contains…
…a network of fibres called the cytoskeleton, which give the cell strength and rigidity and also control movement within the cell.
Plant cells are surrounded by…
…a rigid cell wall and contain a large membrane bound vacuole and chloroplasts.
Despite their differences, prokaryotic and eukaryotic cells have many …
…biochemical pathways in common – thus believed to have descended from the same ancestral cell.
Size of prokaryotes?
2um (2x10-6m)
Amount of dna in prokaryotes?
1.36 mm
Number of genes in prokaryotes?
4377
DNA organisation of prokaryotes?
1 circular chromosome in nucleoid
Size of eukaryotes?
10 – 100 mm
(1x10-5 – 1x10-4 m)
Amount of DNA in eukaryotes?
990 mm
Number of genes in eukaryotes?
30-38000
DNA organisation of eukaryotes?
2 or more chromosomes in membrane bound nucleus
The scale in microscopy is…
…logarithmic. Each unit is 10 times bigger than the previous unit.
Describe how Standard Light Microscopy: The compound microscope works.
Uses UV-visible light and several lenses to magnify the image of a specimen under study.
Describe how Electron microscopy (EM): transmission EM/ scanning EM works.
Fundamental principles similar to light microscopy except electromagnetic lenses focus a high velocity electron beam under high vacuum.
Example of microscope of standard light microscopy?
The compound microscope
Example of microscope of electron microscope.
transmission EM/ scanning EM
WHats the resolving power of the compound microscope (bright-field microscopy)?
0.2um (1 x 10-7 m)
Describe Confocal and Immunofluorescence microscopy
Fluorescent antibodies ‘stain’ specific organelles/structures within the cell.
Confocal scanning microscope (which looks at a single focal plane) creates much sharper images.
Describe Time-Lapse Microscopy.
- Saccharomyces cerevisae
- Treated with a-mating factor
- Picture taken every 3 minutes for 16 hours.
In Electron microscopy (EM): transmission EM / scanning EM…
…Heavy metal stains scatter (diffract) the electrons and appear dark in the image
Describe Transmission electron microscopy
- Passes an electron beam through a sample.
- Very thin samples (50-100nm) need to be prepared and stained with heavy metals (gold / osmium).
Resolving power of Transmission electron microscopy?
50pm (5 x 10-11 m)
Describe Scanning electron microscopy
Sample is coated with a thin layer of heavy metal (platinum) and the electron beam scans the surface. The image is formed from secondary electrons given off by the sample.
Resolving power of Scanning electron microscopy.
Resolving power: 10nm (1 x 10-8 m)
The plasma membrane forms…
…the boundary between the external and internal environment of the cell.
What is the phospholipid bilayer comprised of?
- Hydrophilic phosphate head groups.
- Hydrophobic lipid tails
Describe the Hydrophilic phosphate head groups
orientate toward the aqueous internal / external environments
Describe Hydrophobic lipid tails
orientate towards each other.
The phospholipid bilayer / plasma membrane contains…
…proteins embedded in the membrane: integral membrane proteins
Plasma membrane is …
…impermeable to most molecules except CO2, O2 and water
What is the nucleus surrounded by?
Surrounded by a double membrane
Describe the inner membrane of the nucleus’ double membrane?
Inner: defines the nucleus
Describe the outer membrane of the nucleus’ double membrane?
Outer: continuous with rough endoplasmic reticulum (ER)
What is the nucleolus?
nuclear organizer, RNA / Ribosome synthesis occurs here.
What do the nuclear pores do?
Nuclear pores serve as channels regulating the movement of material between the nucleus and the cytoplasm
What does the chromatin do?
combination of DNA and protein
What does the Nucleoplasm do?
equivalent to the cytoplasm but in the nucleus – nucleotides and enzymes are dissolved in here.
What is the The Endoplasmic Reticulum (ER)?
Interconnected network of internal membranes, responsible for the synthesis of membrane lipids and protein destined for other organelles, membranes and secretion.
THere are two types of endoplasmic reticulum which are…
Rough Endoplasmic Reticulum and Smooth Endoplasmic Reticulum
What is the Smooth Endoplasmic Reticulum?
site of fatty acid and phospholipid synthesis
Why is the rough endoplasmic reticulum rough?
its studded with ribosomes, hence the rough appearance.
Proteins from the rough ER move by …
…transport vesicles to the Golgi apparatus, where further processing of the protein occurs.
Golgi has three defined regions…
- Cis (same)
- Medial (middle)
- Trans (away)
What does the golgi sort?
the golgi sorts proteins so that they end up at their correct cellular destinations by recognising ‘tags’ encoded within the protein.
The mitochondrion is known as…
…The ‘power plant’ of the cell
The mitochondrion completes…
the aerobic degradation of glucose
Respiration equation?
C6H12O6 + 6 O2 —> CO2 + H2O + ENERGY
Most eukaryotic cells contain many…
…mitochondria
Mitochondria have a…
…double membrane
Function of the inner membrane of the mitochondrial double membrane?
impermeable and has a large number of foldings called cristae.
Why is the double membrane of the mitochondrial double membrane permeable?
permeable due to presence of porins (proteins that allow the passage of small molecules)
Mitochondria also contain its…
…own DNA (mitochondrial DNA), located in the matrix.
The Lysosome contain a…
…battery of degradative enzymes.
The Lysosomes are…
…Acidic with a pH of 5
Function of lysosomes?
- Help to break down complex DNA, proteins, lipids etc into their component parts.
- Also breakdown organelles that have outlived their usefulness.
Where is The Peroxisome found?
Found in animal and plant cells.
What does the peroxisome contain?
- Contain enzymes that break down fatty acids and amino acids and as a by-product generate hydrogen peroxide (H2O2)
- Many peroxisomes contain a crystalline array of catalase.
How is hydrogen peroxide neutralised?
This potentially damaging chemical is neutralized by large amounts of catalase within the peroxisome.
the chloroplast is…
…the site of photosynthesis
What is the chloroplast surrounded by?
Surrounded by a double membrane -
- Inner: impermeable
- Outer: permeable to small molecules
Describe internal membrane of chloroplasts
Further extensive internal membrane system made of thylakoid vesicles arranged in stacks called grana.
Thylakoid vesicles contain …
…chlorophyll and other pigments
In chloroplasts, a space called the stroma surrounds …
…the grana
Chloroplasts (like mitochondria) contain …
…their own dna.
It was orignally thought that the cytosol was…
…a soup
Cytosol is the site of…
…glycolysis.
THe cytosol is high in…
…protein concentration
The cytosol contains…
…glycogen (storage granules)
How many classes of fibres in the cytoskeleton?
three
What are the different classes of fibres in the cytoskeleton?
1) Microtubules:
2) Microfilaments
3) Intermediate filaments
- These help to maintain cell shape and mobility
Cilia and Flagella are…
…Motile extensions of the plasma membrane
What runs through the cores of cilia?
Microtubule filaments run through the cores of cilia
Function of flagella?
Flagella are used to propel the cell, e.g. bacterium or sperm cell.
Function of cilia?
Cilia beat back and forwards, flagella rotate
What kind of membrane do vacuoles have?
Semi-permeable membrane
Describe semi-permeable membrane
Permeable to water, but
Impermeable to small molecules contained within the vacuole.
Describe formation of turgor.
entry of water causes the vacuole to expand, creating a turgor inside the cell, balanced by the rigidity of the cell wall.
The vacuole stores:
Water
Ions
Waste products
Food materials (sucrose)
Excess nitrogenous compounds (amino acids)
Whats the cell wall in plant cells used for?
- Impart strength and rigidity under turgor pressure.
- It contributes to plant form by growing as the plant cells expand.
Whats the cell wall in plant cells composed of?
Primarily composed of cellulose (polysaccharide of glucose sugar)
or lignin (complex polymer of phenolic compounds).
Thje cell wall in plant cells acts as a…
A physical barrier to many fungi, bacteria and other organisms that may cause disease.
THe cell wall of plant cells may also contain?
May also contain waxes to prevent plant tissues and proteins from drying out.
A variety of proteins and polysaccharides form …
…specific contacts and junctions between cells.
The Extra-cellular Matrix imparts…
…strength and rigidity to multicellular tissues.
What are connective tissues?
extracellular spaces between cells consisting mainly of collagen
The connective tissue is rich in…
…rich in proteoglycans - form the ground substance in which collagen and other connective tissue fibres are embedded.
