Unit 2.1 + 2.2 - Cells Flashcards
Function of Cell-surface Membrane. x2
Regulates the movement of substances into and out of the cell.
It has receptor molecules on it which allow it to respond to chemicals like hormones.
Structure of Nucleus x4
Surrounded by a double membrane called a nuclear envelope.
The nuclear envelope contains many pores called nuclear pores
Contains chromosomes which are made from protein bound linear DNA
Also contains one or more nucleolus
Function of Nucleus x3
Controls cells activities by controlling the transcription of DNA which contains instructions to make proteins.
Nuclear pores allow substances to move between the nucleus and cytoplasm.
Nucleolus makes ribosomes
Structure of a Mitochondrion x2
Oval shaped with a double membrane:
the inner membrane is folded to form structures called cristae which contain enzymes involved in respiration
Function of a Mitochondrion x1
Site of aerobic respiration and produces ATP
Function of Chloroplasts
site of photosynthesis which occurs in both the stroma and the grana
Structure of Chloroplasts x 5
Small, flattened structure
Surrounded by double membrane
Contains membranes inside called thylakoid membranes.
Thylakoid membranes stack up to form grana
Contains a thick fluid called stroma
Structure of Golgi Apparatus and Golgi Vessicles
GA - Group of fluid filled, membrane bound, flattened sacks.
GV - Small fluid filled sack surrounded by a membrane found in the cytoplasm on the edge of the GA.
Function of Golgi Apparatus- x2
Processes and packages new lipids and proteins.
Makes lysosomes
Function of Golgi Vessicles
Stores lipids and proteins made by the golgi apparatus and transports them out of the cell.
Structure of lysosomes
A type of golgi vesicle that is a spherical organelle, surrounded by a membrane with no clear internal structure.
Function of lysosomes
Contains digestive enzymes called lysozymes and are used to digest invading cells or to break down worn out components of the cells.
Structure of rough endoplasmic reticulum and SER
RER - A system of membranes enclosing a fluid filled space. Surface is covered with ribosomes.
SER - similar to RER but no ribosomes
Function of Rough Endoplasmic Reticulum
Synthesises and transports proteins around the cell
Function of Smooth Endoplasmic Reticulum
Synthesises and processes lipids
Structure of Ribosome?
Small organelle made of proteins and RNA.
Not surrounded by a membrane
Function of Ribosomes?
Protein synthesis
Structure of cell wall?
Rigid structure that surrounds algae, plants and fungi cells.
Made of cellulose in plants and algae but chitin in fungi
Function of the cell wall?
Supports cell and prevents it from changing shape or bursting
Structure of the vacuole
A membrane bound organelle containing cell sap (Weak solution of sugar and salts)
Surrounding membrane is called the tonoplast
Function of the vacuole?
Helps maintain pressure inside the cell
Involved in the isolation of unwanted chemicals inside the cell.
How does an optical microscope work?
Specimens are mounted in water and stained to increase contrast
Rays of light are passed through specimen
Different parts of the specimen absorb different wavelengths of light. More dense = darker
Different shades of light are focused through 2 glass lenses
Image is viewed directly through the eyepiece
Benefits of an optical microscope?
Can be used to view live samples
Limitations of an optical microscope?
2D image
Low mag and res
How does a TEM work?
Specimens are prepared with salts of heavy metal and placed in a vacuum
An electron generated by an electron gun passes through the sample.
More dense regions absorb more electrons and appear darker
Electrons are focused through electromagnetic lenses
Image is produced on a screen.
Benefits of a TEM
Relatively high mag and res
Limitations of a TEM
Cannot look at living specimens as in a vacuum
2d image
Specimen prep is complex so artefacts can be introduced
Sample must be very thin so electrons can pass through
How does an SEM work
Specimens are chemically treated and covered with a film of gold
An electrons beam is generated by an electron gun onto the specimen
Images are formed from the electrons reflecting back from the specimen
Electrons focused through electromagnetic lenses
3DImage produced on a screen
Benefits of an SEM
3D image
Relatively high mag and res
Limitations of an SEM
No live specimens due to vacuum
Complex prep so artefacts may be introduced
Difference between eukaryotic and prokaryotic cells x7
Eukaryotic much bigger
Prokaryotic have no membrane bound organelles
Prokaryotic has no nucleus and the DNA is found in a circular molecule in the cytoplasm
Prokaryotic have smaller ribosomes
Cell wall made of murein instead of cellulose or chitin which is found in eukaryotic cell walls
Prokaryotic may have a capsule
May have one or more plasmids
Role of the capsule in bacterial cells?
Protects bacterium from other cells and helps groups of bacteria to stick together for further protection
Role of plasmids in bacterial cells
Possesses genes that may aid the survival of bacteria in adverse conditions eg. produces enzymes that break down antibiotics
Why are viruses nonliving?
No nucleus
Must live off another organism
Inert until they enter the host cell and then they can reproduce
Describe the structure of a virus?
A core of genetic material (DNA or RNA) which is surrounded by a protein coat called a capsid which has attachment proteins coming off.
Some proteins have an envelope that surrounds the capsid made from lipids.
Why can viruses not reproduce themselves?
A cellular and contain no mitochondria or ribosomes so can create no proteins.
Role of attachment proteins in viruses?
Bind onto suitable host cells
Why do viruses make you feel ill?
Destroy/damage cells when they leave the host cell
Why are viruses difficult to treat?
They replicate inside host cells which makes them hard to individually target
Steps of viral replication?
- Virus attaches to the host cell receptor proteins
- Virus releases its genetic material into the host cell
- The host cell’s organelles replicate the genetic material
- The viral components assemble
- Replicated viruses are released from the host cell
What are the stages of the cell cycle?
Interphase
Prophase
Metaphase
Anaphase
Telephase
What occurs during interphase
Normal functions
Cell’s DNA is unraveled and replicated
Organelles replicate and ATP production increases
Describe the structure of a chromosome in mitosis
A chromosome is formed of two chromatids joined together by a centromere
The two chromatids joined by the same centromere are called sister chromatids
What occurs during prophase?
Chromosomes condense and become shorter and fatter
The centrioles move towards opposite ends of the cell and form the spindle fibers
Nuclear envelope disappears
What occurs during metaphase?
The chromosomes line up down the centre of the cell and become attached to the spindle by the centromere
What occurs during anaphase?
Centromeres divide which separates the sister chromatids
Spindles contract which pulls the chromatids to opposite centrioles
Making the chromatids appear v shaped
What occurs during telophase?
Chromatids uncoil and become long and thin again - now called chromosomes
Nuclear envelope forms around each group of chromosomes and the cytoplasm divides in two through cytokinesis
Leaving two identical daughter cells
What is the mitotic index?
Shows the proportion of cells undergoing mitosis at a given time
Mitotic index = ?
Number of cells in mitosis / total number of cells
Time spent in a specific stage of mitosis?
Number of cells in a specific stage of mitosis / total number of cells observed = mitotic index
Mitotic index x time for one cycle
What chemicals did we use for the mitotic index practical? Why?
Ethanoic alcohol - fixative that preserves cell structure (prevents mitosis)
Toluidine blue - Stains chromosomes so they are visible
HCl - breaks down cells walls and separates the cells so they can be squashed
What are the phases of interphase called? and what happens
G1
S
G2
What occurs in G1 of interphase
Cell growth
New proteins are made
Organelles replicate
ATP production
What occurs in S phase of interphase?
Synthesis phase:
DNA replicates
What occurs in G2 of interphase?
Cell growth
Spindle proteins made
ATP production
What occurs in M phase of the cell cycle?
Prophase
Metaphase
Anaphase
Telephase
How do prokaryotic cells replicate?
Through binary fission
Describe the steps of binary fission?
- Circular DNA (only once) and Plasmids replicate (can be multiple)
- Circular DNA attaches to cell membrane and the cell elongates - DNA moves to opposite ends
- Cell membrane begins to grow between the two DNA molecules, this divides the cytoplasm in two
- New cell wall forms between the two DNA molecules and this divides the cell into two identical daughter cells
What is the difference between cell division in cancer and mitosis?
Mitosis = controlled
Cancer = uncontrolled
How do mutations develop tumors?
Mutations in cell cycle genes, eg the gene that controls cell division lead to uncontrolled growth.
How do cancer treatments work? and why are they more likely to kill tumor cells than normal cells?
Try to limit the rate of cell division
More likely to kill tumour cells as they replicate more frequently
What are phospholipids made from?
Hydrophobic hydrocarbon tail
Hydrophilic phosphate head
Role of phospholipids in a cell membrane? x3
Allow lipid soluble substances to enter and leave the cell
Prevent water soluble substances from entering and leaving the cell
Makes the membrane flexible and self sealing
Role of proteins in a cell membrane? x5
Structural support
Act as channels which transport water soluble substances across the membrane
Allow transport through carrier proteins
Act as receptors
Act as enzymes
Function of cholesterol in cell membranes? x3
Reduce lateral movement of other molecules
Makes the membrane less fluid at high temperatures
Reduces water leakage and dissolved ions from the cell
How does cholesterol prevent water leakage in cell membranes?
They are very hydrophobic
Structure of a glycoprotein in a cell membrane?
Carbohydrate chain which is covalently bonded to a membrane protein
Function of glycoproteins in cell membranes? x3
Allows cells to recognise one another
Helps cells to attach to one another and form tissues
Acts as receptors
Functions of a glycolipid?
Allows cells to recognise one another
Helps maintain the stability of a membrane
Helps cells to attatch to one another and form tissues
2 properties a drug should have if they are to pass quickly through a membrane
lipid soluble
uncharged
small
Why is it called the fluid mosaic model?
Fluid: Phospholipid molecules move relative to one another which creates a flexible structure which is constantly changing shape.
Mosaic: Proteins vary in shape and size
