Cell Structure And Microscopy Flashcards
Structure of double nuclear envelope
A double membrane which compartmentalises the Nucleus and prevents damage. This protects the DNA.
Structure of nuclear pores
Allows molecules to enter (e.g. nucleotides for DNA replication) and leave the cell (e.g mRNA leaves the cell).
Structure of Nucleolus
Composed of RNA and proteins.
Structure of Chromatin
DNA (with associated histone proteins).
Contains the Genetic Code which controls the activity of the cell.
Function of nucleus
1) Controls all the activity of the cell.
2) The Genetic Code (DNA) of the cell is stored, replicated, and copied into RNA (transcribed).
3) The Nucleus is attached to the Rough ER so the mRNA can easily get to ribosomes.
Function of Nucleolus
Produce and assemble the cells ribosomes- site of ribosome production
Function of nuclear envelope
Membrane that divides the nucleus and prevents damage- protects DNA
Structure of Rough Endoplasmic Reticulum
** Stacks of flattened membranes bound** (fluid filled sacs) which form sheets called cisternae.
Attached to the nucleus and studded with ribosomes.
Structure of smooth Endoplasmic Reticulum
** Stacks of flattened membranes bound** (fluid filed) sacs which form sheets called cisternae.
Attached to the nucleus
Does not have ribosomes ( is a system of interconnecetd tubes)
Function of Rough Endoplasmic Reticulum
Site of protein synthesis and glycoproteins synthesis
Transport proteins that synthesised on the attached ribosomes. Some proteins will be secreted by the cell whilst others will be placed on the surface of the cell membrane.
Function of smooth Endoplasmic Reticulum
It mostly creates lipids which cells need along with carbohydrates and steroid syntheis , and storage
Structure of Golgi Apparatus
** Stacks of flattened , membranes bound** (fluid filed) sacs which form sheets called cisternae.
Continuously formed from the ER at one end and budding off as Golgi vesicles at the other
Function of Golgi Apparatus
• Allows internal transport.
• Receives proteins from the RER
• Modifies and processes molecules (such as new lipids and proteins) and packages them into vesicles.
• These may be secretory vesicles (if the proteins need to leave the cell) or lysosomes (which stay in the cell).
• Makes lysosomes
• Lipid synthesis
Structure of ribosomes
• A 2 subunit organelle (80S in size in eukaryotes)
• Made from RNA and protein.
• Not membrane bound.
• Very small organelles: about 22nm in diameter.
• Found free floating in the cytoplasm or attached to the Rough ER
Function of ribosomes
-The site of translation in protein synthesis
-They assemble amino acids into chains of protein using mRNA
Structure of Mitochondrion
-Oval shape
-surrounded by 2 membranes ( double membrane)
_The inner membrane forms finger-like structure called cristae whic increases the surface area
-The solution , matrix contains enzymes for respiration
-Contains mitochondrial DNA which enable it to reproduce and create enzymes
Function of Mitochondrion
-Site of aerobic respiration
-Release ATP during respiration (energy carrier in cells)
Structure of lysosomes
Spherical sacs surrounded by a single membrane
Function of lysosomes
Contain a powerful hydrolytic digestive enzymes known as lysozymes
Break down worn components of the cell or digest invading cells
Structure of centrioles
Component of cytoskeleton composed of many microtubules
Small hollow cylinder that occur in parts next to the nucleus in animal cells
Each centriole contains a ring of 9 triple microtubules
Function of centrioles
Copies itself during cell division and then helps to form the spindle in cell division
Involved in the organisation of chromosomes in cell division
Structure of cilia
‘Hair like’ extensions that protrude from some animal cell types.
In a cross section has an outer membrane and a ring of 9 pairs of protein microtubules inside with two in the middle (9 = 2 arrangement)
Arrangement allows movement
function of cilia
Sensory function (e.g nose), beat creating a current to move/waft fluid/ mucous/ objects .
For locomotion
Structure of plasma membrane
The membrane found on the surface of animal cells and inside the cell wall of plant and prokaryotic cells
phospholipid bilayer ( proteins and cholesterol within it)
Composed of glycoproteins and glycolipids on the surface
Function of plasma membrane
• Regulates the movement of substances into and out of the cell.
• Contains receptor molecules (glycoproteins and glycolipids) which allow it to respond to chemical like hormones
Cholesterol provides strength and reduces fluidity
proteins are for transport
Structure of cytoskeleton
Made up of three structural component：
Microfilaments
Microtubules
Intermediate fibres
Function of cytoskeleton
Microfilaments- Fibres made from the protein actin. They are responsible for movement of the cell and cytoplasm during cytokinesis
Microtubules- Formed by the globular protein tubulin. They polymerise to form tubes that determine the shape of the cell. They also act as tracks for organelles moving forward.
Intermediate fibres- Gives strength to cells and helps maintain integrity.
Structure of flagella
similar to cilia but longer.
• They protrude from the cell surface and are surrounded by the plasma membrane.
• Like cilia they have a 9 +2 arrangement.
Function of flagella
• (Whip-like) enables a cells mobility.
• The microtubules contract to make the flagellum move.
• Propel cells forward e.g. sperm cells.
Structure of chloroplast
• Double membrane which encloses the stroma.
• Stroma contains: Starch grains, lipid stores, DNA, RNA, ribosomes.
• Series of membrane-bound flattened sacs called thylakoids in the stroma. Thylakoids stacked together are called grana.
• Grana are linked together by lamellae.
• The grana contain chlorophyll
Function of chloroplast
Photsynthetic reactions
The stroma contains enzymes for the light-independent stage of photosynthesis.
Structure of cell wall
Made of B-cellulose microfibrils (complex carbohydrate) in plants / chitin (fungi) / polysaccharides (prokaryotic)
• Cell wall is fully permeable to substances
• Thin layer called the middle lamella which marks the boundary between adjacent cell walls and ‘cements’ adjacent cells together.
Function of cell wall
Gives the plant mechanical strength
• Gives the plant cell support and it’s shape
• Contents of plant cell can ‘push’ against the cell wall (turgid cell). This gives the cell (and the whole plant) good support.
Structure of Large permanent vacuole
• Single membrane bound (membrane is called a tonoplast).
• Contains a fluid called cell sap (solution of mineral salts, sugars, amino acids, wastes etc).
• Selectively permeable barrier
Function of Large permanent vacuole
• Stores cell cap
• Support herbaceous plants by making cells turgid.
• Helps maintain shape and gives support by maintaining ** turgor pressure** .
• Sugars and amino acids act as a temporary food store.
Explain the Interrelationships of protein production and secretion
1)DNA in the nucleus contains the genetic code to make protein.
2) The particular gene (e.g. insulin) is copied by mRNA, which takes the copy of the gene out of
the nucleus via the nuclear pore to the ribosome (on the rough ER).
3) The protein is synthesized on the ribosome bound to the Rough ER where it then passes into the cisternae of the rough ER and it is packaged into a vesicle.
4) The vesicle moves to the golgi apparatus (via the microtubules of the cytoskeleton), and fuses with the golgi apparatus.
5) The protein enters the golgi apparatus where it processes and structurally modifies the protein e.g. adds a carbohydrate chain.
6) The Golgi Apparatus repackages the protein into a secretory vesicle where it travels along the microtubules and fuses with the cell surface membrane.
7) Contents of the vesicle (i.e. the protein) is released by exocytosis.
