cell structure Flashcards
what is the function of mitochondria
- the production of ATP, through respiration
2. regulating cellular metabolism
explain the structure of mitochondria
- double membrane, rod shaped organelle
- size range of 0.5-1 micrometre
- made up of inner membrane, outer membrane and a matrix
- membranes are both made out of proteins and phospholipid layers, separated by an intermembrane space
- the inner membrane has many folds, forming a cristae, and increasing surface area
- mitochondrial matrix is a fluid that contains enzymes and proteins
what is the function of Golgi apparatus
- modification and sorting of lipids and proteins
2. produces secretory vesicles to eject modified molecules from the cell
explain the structure of Golgi apparatus
- Membrane bound organelle
- Made up of 5-8 folds called Cisternae
- Cisternae contain specific enzymes so there are five functional regions which modify proteins
what is the function of the nucleus
- Controls and regulates the activities of the cells
2. Carries the genes
explain the structure of the nucleus
- chromatin and nucleolus surrounded by a nuclear envelope with nuclear pores
- nuclear pores regulate the movement of molecules from the nucleus to the cytoplasm
what is the function of chloroplasts
- synthesise food by the process of photosynthesis
2. chloroplasts contain chlorophyll which traps solar energy
explain the structure of chloroplasts
- double membrane organelle that contains grana and stroma
- grana are made up of stacks of thylakoids, thylakoids contain chloroplasts
- stroma is the homogenous matrix and is similar to cytoplasm, it contains enzymes, DNA and ribosomes
what is the function of lysosomes
- The key function of lysosomes is digestion and removal of waste
explain the structure of lysosomes
- membrane bound organelles with a singular membrane
2. they typically range in size from 0.1 μm to 0.6 μm
what is the function of ribosomes
- assembles amino acids to form proteins (protein synthesis)
explain the structure of ribosomes
- ribosomes range in size eg, prokaryotes, 70s & eukaryotes, 80s
- ribosomes have two sub-units both contain protein and ribonucleic acid
- smaller sub-unit, where the mRNA is bound and decoded
- larger sub-unit, where amino acid is added
what is the function of smooth endo-plasmic reticulum
- responsible for the synthesis of essential lipids
- responsible for the production and secretion of steroid hormones
- transports the products of RER to other organelles, mostly golgi
explain the structure of smooth endo-plasmic reticulum
- A series of flattened sacs that are not associated with ribosomes
what is the function of a cell wall
- the cell wall separates the interior contents of the cell from the exterior environment
explain the structure of a cell wall
- made of chitin in fungi
2. made of cellulose in plants
what is the function of a cell vacuole
- storage of food and other nutrients needed by the cell to survive
explain the structure of a cell vacuole
- surrounded by a membrane called a tonoplast
2. contains cell sap
what is the function of rough endo-plasmic reticulum
- responsible for protein synthesis
explain the structure of rough endo-plasmic reticulum
- a series of flattened sac with associated ribosomes
Define cell fractionation
The process where cells are broken up and different organelles are separated
What must happen before cell fractionation can begin
The tissue is placed in a cold isotonic buffered solution
Explain each why, before cell fractionation, the tissue is placed in a cold isotonic buffered solution
Cold- Reduces enzyme activity that may break down the organelles
Isotonic- has the same water potential as the tissue so it prevents the organelles from bursting due to osmosis
Buffered- to prevent damage to enzymes, buffers maintains a constant PH
What are the steps of cell fractionation
- Tissue is placed in cold isotonic buffered solution
- homogenisation
- Homogenate is filtered to remove and complete cells
- centrifugation
Explain the process of homogenisation
- Cells are broken up by a homogeniser
2. This releases the organelles
Explain the process of centrifugation
- Homogenate is spun at a low speed
- The heavier organelles are pushed to the bottom of the tube due to the force generated
- The supernatant is then transferred into a new tube, leaving the pellets (of the organelles) in the other test tube
- The supernatant is then spun again at a higher speed to separate the lighter organelles
- The process is repeated
What is the order of cells separated during centrifugation (remember the acronym)
Nucleus Chloroplasts Mitochondria Lysosomes Endo-plasmic Reticulum Ribosomes
Give one disadvantage and one advantage of an optical light microscope
Disadvantage-
- Samples must be very thin
- Resolution is limited to lights wave length
- 2D image
Advantages-
- Inexpensive
- Portable
- sample can be living
Give one disadvantage and one advantage of a transmission electron microscope
Disadvantages-
- Sample must be thin
- Sample must be dead
- Must be done in a vacuum
- Often find artefacts
Advantages-
- High resolution
- Can see the internal structure
- Higher magnification
Give one disadvantage and one advantage of a scanning electron microscope
Disadvantages-
- Sample must be dead
- Must be done in a vacuum
- Can’t see the internal structure
Advantages-
- Sample can be thick
- 3D image
What is the magnification equation
Image size
Magnification= ————————
Actual size
How many micrometres in a millimetre
How would you change the units from mm-um and um-mm
1000
mm-um= x1000 um-mm= ‘/, 1000
Give the 4 stages of the cell cycle
- G1
- S
- G2
- Mitosis
Explain G1, phase of the cell cycle
The cells contents are duplicated
Explain G2, phase in the cell cycle
The cell check for errors
Explain S, phase in the cell cycle
Chromosomes are duplicated
What is the structure of chromosomes at G1
Single chromatid
What is the structure of chromosomes at S phase
Sister chromatid joined together at the centromere
What part(s) of the cell cycle make up interphase
G1, S, G2
What happens during mitosis
The cell divides into two identical daughter cells
what are the differences between eukaryotes and prokaryotes
- prokaryotes have no true nucleus while eukaryotes have a distinct nucleus with a nuclear envelope
- in prokaryotes DNA is not associated with proteins but in eukaryotes it is associated with histone proteins
- prokaryotes some of the DNA is in circular stands (plasmids) whilst in eukaryotes it is linear
- prokaryotes have no membrane bound organelles but eukaryotes have membrane bound organelles such as mitochondria
- prokaryotes have smaller ribosomes (70S) whilst eukaryotes have larger ribosomes (80S)
State and explain the two types of cell division
- Mitosis, produces two daughter cells that have the same number of chromosomes as the parent cell
- Meiosis, produces four daughter cells with half the number of chromosomes as the parent cells
Explain prophase
- In prophase the chromosomes first become visible
- The nuclear envelope disintegrates
- the centrioles move to the poles of the cell and form spindle fibres
Explain metaphase
- The centromere attaches to the spindle fibres
- They appear to be lined up along the equator of the cell
Explain Anaphase
- The centromeres split pulling the chromatids apart
- The chromatids are pulled by the spindle fibres to opposite poles
- We now refer to the separated chromatids as chromosomes
Explain Telophase
- spindle fibres disintegrate
- a nuclear envelope forms around the chromosomes
- the chromosomes uncoil and form chromatin
How does cell division occur in prokaryotes
describe the process
Binary fission
- DNA replicates
- plasmid replicates
- A cell membrane forms between the two DNA molecules
- A cell wall forms and separates the two new identical daughter cells
