3. Cells Flashcards
Name all the sub-cellular structures in an animal cell
- nucleus
- cell-surface membrane
- mitochondria
- Golgi apparatus
- lysosomes
- ribosomes
- rough & smooth endoplasmic reticulum
Name all the sub-cellular structures ONLY found in a plant cell
- chloroplasts
- cell wall
- cell vacuole
Describe the structure of the nucleus
- nuclear envelope. A double membrane with endoplasmic reticulum and often ribosomes on its surface. Controls the entry of substances.
- nuclear pores. Allows passage of large molecules out of the nucleus
- nucleoplasm
- chromosomes
- nucleolus. Manufactures ribosomal RNA and assembles the ribosomes.
Describe the function of the nucleus
- acts of the control centre of the cell through the production of mRNA and tRNA
- retains gentic material in the form of DNA and chromosomes
- manufacture ribosomal RNA and ribosomes
Describe the structure of the mitochondria
- double membrane. Controls the entry of substances.
- cristae. The folds created by the inner membrane provide a large SA for attachment of enzymes
- matrix. Within the inner membrane and contains protein, lipid, ribosomes. DNA and enzymes involved in respiration that allows the mitochondria to control the production of their own proteins.
Describe the function of mitochondria
-site of aerobic respiration (krebs and oxidative phosphorylation)
Describe the structure of chloroplasts
- chloroplast envelope. Double plasma membrane
- the grana. Stacks of thylakoids which chlorophyll is kept within. This is where the first stage of photosynthesis
- The stroma. Fluid filled matrix where second stage of photosynthesis takes place.
Describe how chloroplasts are adapted to their function
- granal membranes provide large SA for the attachment of chlorophyll, electron carriers and enzymes that carry out the first stage of photosynthesis.
- fluid of stroma possesses all the enzymes needed to make sugars in the second stage of photosynthesis.
- chloroplasts contain both DNA and ribosomes so they can quickly and easily manufacture proteins needed for photosynthesis
Describe the difference in structure if RER and SER
RER has ribosomes present on the outer surface of the membranes, SER does not and is more tubular in appearance
Describe the function of RER
- provide a large SA for the synthesis of proteins and glycoproteins
- transport substances especially proteins throughout the cell
Describe the function of SER
- synthesis store and transport lipids
- synthesise store and transport carbohydrates
Describe the function of Golgi apparatus
- add carbohydrate to proteins to form glycoproteins
- produce secretory enzymes
- secrete carbohydrates
- transport, modify and store lipids
- form lysosomes
Describe the function of lysosomes
- hydrolyse substances ingested by phagocytic cells
- release enzymes to outside the cell (exocytosis) in order to destroy material around the cell
- digest damaged organelles to recycle substances
- break down of cells after they have died (autolysis)
What are the two kinds of ribosomes
- 80s are found in eukaryotic cells, 25 nm in diameter
- 70s are found in prokaryotic cells, mitochondria and chloroplasts and are slightly smaller
Name the constituent parts of a ribosome
- RNA
- protein
What is the function of a ribosome
They are the site of protein synthesis
Describe the structure of a cell wall
- consist of a number of polysaccharides such as cellulose
- There is a thin layer, called the middle lamella which marks the boundary between adjacent cells.
Describe the function of a cell wall
To provide mechanical strength
Describe cell walls in algae and fungi
- in algae they are made of cellulose and or glycoproteins
- in fungi they are made from a nitrogenous substance called chitin, a polysaccharide called glycan and glycoproteins
Describe the structure of a bacterial cell
- cell wall, made of murein
- slime capsule, around this wall
- cell surface membrane, inside the cell wall
- cytoplasm
- ribosomes, 70s
- circular DNA and plasmids
- flagella
Describe differences between eukaryotic and prokaryotic cells
- pro have no nucleus, eu have distinct nucleus
- pro DNA is not associated with proteins, eu is associated with proteins called histones
- circular DNA and plasmids, linear DNA and no plasmids
- pro has no membrane bound organelles, eu has
- ribosomes are different sizes
- pro cell wall made of murein and eu is cellulose
- pro may have slime capsule, eu doesn’t
Describe the structure of a virus
- contain genetic material (RNA)
- reverse transcriptase
- capsid enclosing genetic material and enzymes
- lipid envelope surrounding everything
- attachment proteins on liquid envelope
Describe the limitations of an optical microscope
- poor resolution
- poor magnification
Describe the advantages of a transmission electron microscope
- high resolution
- high magnification
Describe the limitations of a transmission electron microscope
- system must be in vacuum so living cells cannot be observed
- complex staining process
- specimen must be extremely thin
- image may contain artefacts
Describe the advantages of a scanning electron microscope
- high resolution
- high magnification
- specimen does not need to be thin
Describe the limitations of a scanning electron microscope
- lower resolving power than TEM
- system must be in vacuum so living cells cannot be observed
- complex staining process
- image may contain artefacts
Describe the advantages of an optical microscope
- living cells can be observed
- colour can be observed
Define resolution
The ability to distinguish two points
Define magnification
How many times bigger an image is relative to the object
Magnification equation
mag= image/real
What are the stages of cell fractionation
- homogenation
- ultracentrifugation
Describe and explain the conditions for cell fractionation
- cold, to reduce enzyme activity
- solution same water potential as the tissue, to prevent movement of water via osmosis causing bursting or shrinking
- buffered solution, maintain pH which could alter structure or enzymes
Describe the first step of cell fractionation
In homogenation cells are broken up in a blender which releases organelles from the cell
Describe the second step of cell fractionation
Ultracentrifugation is the process by which the fragments in the filtered homogenate are centrifuged.
- filtrate is spun in centrifuge at low speeds
- densest organelles are forced to the bottom where they form a pellet
- fluid at the top of the tube is removed
- the fluid at the top is transferred and spun at an increased speed
- the next densest organelles are forced to the bottom
- the process is repeated until all the organelles are separated out
Describe the function of a vacuole
- make cells turgid
- contains sugars and amino acids that may act as a temporary food source
- pigments may colour petals to attract pollinating insects
Define a tissue
Collection of similar cells that perform a specific function
Define an organ
A combination of tissues that are coordinated to perform a variety of functions
Define an organ system
A collection of organs that are group together to perform a particular function
What is produced in mitosis
Two daughter cells that have the same number of chromosomes as the parent cell and each other
What is produced in meiosis
Four daughter cells, each with half the number of chromosomes of the parent cell
What is mitosis
Division of a cell that results in each of the genetically identical daughter cells having an exact copy of the DNA of the parent cell
What is the period that precedes mitosis called
Interphase
What happens during interphase
DNA is replicated
Name the stages on mitosis
- prophase
- metaphase
- anaphase
- telephase and cytokinesis
What happens during prophase
- chromosomes first become visible
- centrioles move to the poles
- spindle fibres develop
What happens during metaphase
-spindle fibres attach to centromeres of chromosomes and line them up along the equator
What happens during anaphase
- centromeres divide into two and the spindle fibres pull the individual chromatid pairs to opposite poles
- energy for this is provided by mitochondria
What happens during telophase
- chromosomes reach poles and become thinner until they disappear leaving widely spread chromatin
- spindle fibres disintegrate
- nuclear envelopes and nucleoli reform
- cytokinesis (cytoplasm divides)
What kind of cell division occurs in prokaryotic cells
Binary fission
Describe the steps in binary fission
- circular DNA and plasmids replicate
- cell membrane begins to grows and divides the cytoplasm
- cell walls form between the two molecules of DNA dividing the original cell into two identical daughter cells, each with a single copy of DNA and a variable number of plasmids
How do virus’ replicate
- virus’ are non-living and therefore cannot undergo cell division
- they inject their genetic material into a host cell
- cells machinery assembles this which is a new virus
What are the stages in the cell cycle
- interphase
- mitosis
- cytokinesis
What is cancer
Uncontrolled growth and cell division causing tumours
What is the difference between benign and malignant tumours
- benign tumours grow more slowly and are more compact so are less life threatening
- malignant tumours grow more rapidly and are less compact so are more life threatening
Drugs used to treat cancer usually disrupt the cell cycle, how does it do this
- preventing DNA from replicating
- inhibiting the metaphase stage of mitosis by interfering with spindle formation
What is the problem with cancer treatment
They also disrupt the cell cycle of normal cells.
