3.2 Chapter 3- Cell Structure Flashcards
3.2.1- Cell Structure, 3.3.2- All Cells Arise from other cells
What is evidence all life on earth has a common ancestor?
All life on earth exists as cells with basic common features.
What are difference between cells caused by and what is this evidence for?
Differences between cells- due to the addition of extra features- indirect evidence for evolution.
Define a prokaryote
A single-celled, small simple organism
Define an organelle.
Parts of cells
Where are eukaryotes found?
Plants, algae, fungi, animals
Name the 10 parts of the plant cell on the revision card.
- Cell vacuole
- Smooth endoplasmic reticulum
- Mitochondrion
- Golgi Apparatus
- Cell Wall
- Nuclear envelope
- Nucleolus
- Cell-surface membrane
- Rough Endoplasmic reticulum
- Chloroplast
Name the 11 parts of he animal same on the revision card.
- Cell- surface (plasma) membrane
- Rough endoplasmic reticulum
- Nucleolus
- Nucleus
- Smooth Endoplasmic Reticulum
- Lysosome
- Ribosome
- Nuclear envelope
- Golgi Apparatus
- Cytoplasm
- Mitochondrion
What are the extra features of fungi?
- Multicellular or unicellular
- Like plant cells except chitin cell wall not cellulose and no chloroplasts as don’t photosynthesise
What are the extra features of plant cells?
- Cellulose cell wall
- Vacuole
- Chloroplasts
What are the extra features of Algae?
- Photosynthetic
- Unicellular or multicellular
- Same as plant cells except some have one large chloroplast instead of lots of small ones
What is the cell-surface membrane also known as?
The plasma membrane
What is the structure and position of the cell-surface membrane?
- On the surface of animal cells and just inside the cell wall of other cells
- Made of phospholipids, protiens, carbohydrates
What is the function of th cell-surface membrane?
- Regulates movement of substances into and out of the cell
- Receptor molecules respond to chemicals e.g. hormones
What is the structure of the nucleus?
Hint: 6 features
- Nuclear envelope- double membrane- controls the entry and exit of materials into and out of the nucleus, contains reactions.
- Outer membrane- ribosomes on surface, continuous with Rough Endoplasmic Reticulum
- Nuclear Pores in the nuclear envelope- allow large molecules out of the nucleus e.g. RNA
- Nucleoplasm- jelly like, granular, bulks nucleus
- Chromosomes- consist of linear DNA around histones- protien-bound.
- Nucleolus- makes ribosomal RNA and ribosomes. May be more than one.
What is the function of the nucleus?
- Control centre of the cell- **produces mRNA and tRNA **and controls protien synthesis.
- Stores genetic material as DNA and chromosomes which codes for polypeptides.
- Where transcription and DNA replication occur.
- Produces ribosomal RNA and ribosomes
Draw and label a nucleus.
Answer on revision card
What is the structure of mitochondria?
- Double membrane- controls entry and exit of material.
- Cristae- Inner maembrane folds to form extensions- can cross whole mitochondria, large surface area for the attachment of enzymes in respiration.
- Matrix- like cytoplasm- contains lipids, protiens, DNA, enzymes for respiration and ribosomes.
- Ribosomes- can manufacture own protiens.
What is the function of mitochondria?
- Aerobic respiration
- Produce ATP
Draw a mitochondria.
Answer on revision card.
How are cells with a high metabolic rate adapted?
Large amounts of mitochondria and cristae for large amount of ATP. e.g. epithelial cells- large amount of active transport.
What is the structure of chloroplasts?
- Chloroplast envelope- double membrane- surrounds organelle- highly selective.
- Grana- stacks of up to 100 discs called thylakoids- contain chlorophyll (photosynthetic pigment). Where the first stage of photosynthesis (light absorbtion) happens, granal membranes increase the surface area for photosynthesis- chlorophyll and enzymes can attatch.
- Lamaellae- tubular extensions that join adjacent grana.
- Stoma- matrix where second stage of photosynthesis (sugar synthesis) takes place. Contains starch grains and enzymes for photosynthesis
- DNA and ribosomes- manufacture protiens and enzymes needed for photosynthesis
What is the function of chloroplasts?
Perform photosynthesis in plants and algae.
Draw a chloroplast.
Answer on revision card
What is the structure of the golgi apparatus?
- Cisternae- flattened sacs with hollow vesicles- fluid filled and membrane bound flattened sacs
- Vesicles- on edges of sacs
What are the functions of the Golgi apparatus?
Hint:
- Protiens and lipids produced by the endoplasmic reticulum pass through the Golgi
- The golgi modifies protiens - adds non-protiens e.g. carbs to form glycoprotiens.
- Modifies lipids- adds protiens- lypoprotien.
- ‘Labels’ protiens- sorts them and sends to the right destination
- Packages protiens into golgi vesicles which are pinched off from ends of cisternae to transport protiens
- Forms lysosomes
- Transports modifies and stores lipids
Where is the Golgi well developed?
In secretary cells esp. epithelial cells
Draw a golgi.
Answer on revision card.
What is the structure of a Golgi vesicle?
- Fluid filled sac pinched from golgi cisternae- surrounded by membranes
- In the cytoplasm
What is the function of a golgi vesicle?
- Stores lipids and protiens
- Transports lipids and protiens outside the cell and within the cell along with rough endoplasimic reticulum
- Fuses with cell membrane to release contents
What is the structure of lysosomes?
- Golgi vesicle with enzymes
- Membrane bound
- Contain lysozymes- hydrolytic enzymes that hydrolyse the cell walls of bacteria in the immune system
Where are lysozymes abundant?
In secretary cells e.g. epithelial cells and phagocytes.
What is the function of lysozymes?
- Break down dead cells completely- autolysis
- Digest worn out organelles into useful chemicals
- Contain lysozymes- hydrolytic digestive enzymes- kept seperate by membrane- digest invaders and worn out organelles.
- Isolate enzymes and release them outside the cell or into a phagocytic vesicle (phagosome)
- Hydrolyse material ingested by phagocytes
- Release enzymes outside the cell to destroy material
What is the structure of ribosomes?
- No membrane
- 80s- eukaryotes- larger
- 70s- prokaryotes- smaller- prokaryotes and organelles
- Made of ribosomal RNA and protiens
- 2 subunits- one large and one small- both contain rRNA and protien
Where are ribosomes found?
- In all cells
- In cytoplasm or attatched to RER
- Vast numbers in cells
What is the funtion of ribosomes?
Protien synthesis in translation.
What is the structure of both endoplasmic reticulums?
- Elaborate 3D structure of sheet like membranes- lamellae
- Membranes have fluid inside and enclose tubules and flatenned sacs called cisternae
- Fluid inside
- Continuous with the outer nuclear membrane
What are the additional structures of Rough Endoplasmic Reticulum?
Has ribosomes on outer membrane.
What is the function of Rough Endoplasmic Reticulum?
- Folds and prcoesses protiens made in ribosomes
- Large surface area for synthesising protiens
- Transports materials especially protiens
What are the additional structures of Smooth Endoplasmic Reticulum?
No ribosomes on outer membrane
What is the function of Smooth Endoplasmic Reticulum?
Synthesise, store, process and transport lipids and carbohydrates.
Draw both endoplasmic reticulums.
Answer on revision cards.
What is the structure of the plant cell wall?
- Microfibrils of cellulose in matrix
- Made of polysaccaride- cellulose.
- Middle Lamella- marks boundary between cell walls and cements cell walls together
What is the structure of the cell wall of algae?
Mainly cellulose and glycoprotien?
What is the structure of the cell wall of fungi?
Mainly Chitin and Glycoprotien
What are the functions of the cell wall?
- Strength- stops cell bursting form water pressure.
- Supports cell and plant
- Microfibrils aid in strength
- Stops cells changing shape
- Permeable- allow water to pass along- contribute to water movement
What is the structure of the vacuole?
- Fluid filled sac
- Surrounded by a single membrane called a tonoplast
- Mature cells have one large central vacuole
- Contains cell sap- solution of sugars, amino acids, salts, wastes and pigments
- In plants
What is the function of the vacuole?
- Makes the cell turgid- maintains pressure- keeps cell rigid and supports plants- stops wilting
- Isolates unwanted chemicals
- Temporary food store of amino acids and sugards
- Pigments- attract polinators
How can you deduce the role of a cell and give an e.g.?
- By looking at the number and size of organelles,
- e.g., mitochondria and large number of cristae means a high metabolic rate.
What do all cells perform and what changes after the embryo?
- All cells perform basic functions.
- After the embryo, cells become specialised to perform a specific function by switching genes on and off
- Cell structures e.g. organelles help the function.
How have cells evolved?
Evolbed so can function more efficiently so the whole organism can function.
How do organelles help cells specialise?
Vary in shape, type, size and number
How would you apply knowledge of organelles to specialisation?
- Consider the role of the cell and what features it might need
- e.g. epithelial cells- microvilli- increase surface area of cell-suface membrane- have lots of mitochondria for active transport and extensive endoplasmic reticulum for protien synthesis
How are specialised cells organised?
- Cells
- Tissues
- Organs
- Organ systems
What is the role of a tissue and give an example?
- Group of cells working together to perform a function.
- e.g. epithelial tissue made of epithelial cells line the surface of organs for protection.
What is an organ and given example?
- Made up a combination of tissues that have a variety of functions to help towards one major function.
- e.g. Epithelial tissue and muscular tissue and glandular tissue from stomach.
What is not classified as an organ and why?
Capillaries- tissue made of just one tissue vs arteries and veins which are organs.
What is an organ system and give an example?
- Organs that work together as a single unit to perform functions more efficiently.
- e.g. digestive system
What are the generic features of prokaryotes?
- Single celled organisms
- Much smaller than eukaryotes.
- No membrane bound organelles in the cytoplasm.
How are prokaryotes different from eukaryotes?
- Have a cell wall with murien (glycoprotein- protein and carbohydrate)- protects against damage and supports the cell
- 70s- smaller ribosomes
- No nucleus- circular DNA molecule that floats free in the cytoplasm not associated with proteins, especially histones- strand coiled up.
What do some prokaryotes have but not others?
- Plasmids- one or more circular loops of DNA that contain e.g. antibiotic resistance genes and can be passed between prokaryotes.
- Capsid- secreted slime that protects the prokaryote from the immune system.
- Flagella- hair like structures that rotate to move the cell-one or more
Draw a diagram of a prokaryote and label it.
Answer on revision card.
What are the generic features of viruses?
- Acellular (not cells) and non-living
- Smaller than bacteria- 0.1 micrometers
What is the structure of a virus?
- Nucleic acids- e.g. DNA/ RNA
- Capsid- protien coat that encloses the protien
- Lipid envelope- in some viruses
- Attatchment protiens- stick out of lipid envelope/ capsid- allow viruses to identify and attatch to host cell.
What is the only place viruses can replicate?
Inside the host cell.
Draw and label a diagram of a virus.
Answer on revision card.
How does an optical microscope work?
- Also known as a light microscope.
- Uses light and glass lenses to magnify the image and focus
What is the maximum resolution and magnification in an optical microscope?
- Resolution- 0.2 micrometres
- Magnification- x1500
What are the limits of an optical microscope?
Small resolution and magnification. Can’t see organelles smaller than 0.2 micrometres e.g. ribosomes due to low resolution due to the wavelength of light being too long.
How do electron microscopes have a greater resolving power than optical microscopes?
Electron microscopes have a smaller wavelength than light microscopes.
How many times greater is the resolving power of an electron microscope compared to a light microscope?
1000x the resolution of light
What is the maximum magnification of an electron microscope?
x1,500,000
What what type of image does an electron microscope produce and what does the sample have to be in and why?
- Produces a black and white image
- Sample has to be dead and in vacuum so particles don’t block electrons.
What does TEM stand for?
Transmission Electron Microscope
How does TEM work?
- An electron beam is focused on the specimen using an electromagnet.
- The electrons are transmitted through the specimen, and the denser parts absorb the electrons and less dense parts allow electrons to pass through.
- Denser parts therefore appear darker and lighter parts appear lighter.
- Creates a 2D image of a cross section that can be built up to form a 3D image
What is the resolution of TEM?
1 nanometre- highest of all microscopes.
What are the limitations of using TEM?
- Specimen must be in a vacuum and dead
- Complex staining process and time consuming preparation
- Thinner specimen needed
- Subject to more artefacts
- Produces a black and white- no colour- image
What type of language must you use when comparing microscopes?
Comparative language e.g. more, thinner, greater.
What does SEM stand for?
Scanning electron microscope
How does SEM work?
- Uses an electron magnet to focus a beam of Electrons over the surface of a specimen moving in a regular pattern to scan it
- Scattering of electrons used to build image of contours
- Builds a 3D image by computer of scattered electrons
What are the benefits of SEM over TEM?
- Doesn’t need a thin specimin
- Produces a 3D image
What are the limitations of SEM?
- Specimen must be in a vacuum and dead.
- Black and white image.
- Complex preparation process means more likely to gain artefacts.
- Lower resolution than TEM
How do you measure the size of an image in a light microscope?
- Use an eyepiece graticule- glass disc with scale attatched on eyepiece- usually 10mm
- Calibrate the graticule using a stage micrometer (can’t directly measure due to magnification- calibration often recorded so don’t need to do second time)
- A stage micrometer has a scale on it- usually 2mm- line up and count scales
- Convert both into micrometers then find micrometers per eypeace graticule unit- divide micromiters by number of units above
How do you convert between scales at different magnifications?
- Use a scale factor
- e.g. 40 to 400- divide by 10
What is magnification?
The size of an image compared to the size of an object.
What is the equation for magnification?
Magnification= size of image/ size of object
What is resolution?
- How well a microscope distinguishes two points that are close together.
- If objects are less than the resolving power- blurred together.
- After the resolving point a higher magnification doesn’t improve clarity
- Measure of detail and clarity
What is an artefact?
Objects that are a result of how a specimen is prepared and not naturally part of the specimen.
When are artefacts common?
- In electron microscopes as need a lot of preparation
How can you mitigate the effect of artefacts?
Doing multiple repeats.
How do you prepare a microscope slide?
- Use a temporary mountain e.g. water with a pippet.
- Put thin specimen on drop with tweezers.
- Add a stain
- Add a cover slip with a mounted needle
What is cell fractionation and ultracentrifugation used for?
Used to separate cell components (organelles) to study structure and function.
What solution do you have to put the sample in for ultracentrifugation?
- Cold- to reduce the enzyme activity and stop them breaking down organelles.
- Isotonic- the same water potential to prevent organelles from bursting or shrinking due to osmosis.
- Buffered- ensures no change in pH occurs that would alter organelle proteins.
Describe the next step after putting cells in solution in cell fractionation and ultracentrifugation.
- Homogenisation- place in homogeniser (blender)- bursts membrane and releases organelle.
- Filter to remove large pieces and complete cells.
How does ultracentrifugation work?
- Place homogenate in centrifuge and spin at low speed
- The densest organelles form to the bottom- as seperates organelles in order of density- form sediment or pellet
- The rest of the organelles stay in fluid above called supernatant
- Supernatant poured into new tube and spun at a higher speed- new pellet of different organelles
- Supernatant drained off and repeated at high speeds until less dense and less dense organelles.
What is the ultracentrifugation order?
- Nucelei
- Chloroplasts
- Mitochondria
- Lysosomes
- Endoplasmic reticulum
- Ribosomes
How do all cells originate?
- From other cells.
- Through binary fission, mitosis or meiosis.
What is the cell cycle for?
The cell cycle is needed for growth and repair to replace and add other cells.
How does the cell cycle vary?
Varies in time from cell to cell.
What do all cells not retain in multicellular organisms?
The ability to divide.
Where does the cell cycle begin and end?
- Begins when cells are produced.
- Ends with cell division.
Describe interphase.
- Most of the cell cycle- 90%
- Growth and DNA replication, organelles and ATP increase
- G1- cell grows and more organelles and protiens made.
- S phase- replication of DNA
- G2- more cell growth and protiens needed for cell division are made.
- Cell carries out normal function and prepares to divide.
How is DNA replication carried out in interphase?
- DNA unravels and replicates twice
- DNA ravelled and joined by the centromere.
Draw the diagram of interphase.
Answer on revision card.
What is mitosis, when does it occur and what does it result in?
- Mitosis is the part of the cell cycle where cell division occurs.
- After the G2 stage of interphase.
- Results in two genetically identical daughter cells from a genetically identical parent cell.
What is the structure of a chromosome when mitosis begins?
- Two strands joined at the centromere.
- Strands are called chromatids. and two identical strands are called sister chromatids.
- Produced during interphase
What anagram describes mitosis?
IPMATC
Describe mitosis
- Prophase- chromasomes condense and thicken. Centrioles (organelles) move to opposite poles of hte cell and form spindle fibres from pole to pole (collectively called spindle apparatus). Nucleolus disappears and nuclear envelope breaks down- chromasomes free in the cytoplasm.
- Metaphase- spindle fibres line up chromasomes along the middle of the cell and attatch to the centromere of chromasomes with two chromatids.
- Anaphase- centromere divide chromasomes into two seperate sister chromatids. Spindle fibres pull chormatids to opposite poles by the centromere. Energy provided by mitochondria. Chromatids become chromasomes.
- Telophase- chromasomes reach opposite poles, uncoil, spindle fibres disintegrate, nuclear envelope and nucleolus reform.
- Cytokinesis- cytoplasm divides- 2 genetically identical daughter cells.
What do plants not have during mitosis?
Centrioles
Draw the stages of mitosis.
Answer on revision card.
How do you calculate the time of mitosis stage?
- Put stage over total amount of cells
- Multiply fraction by time
Compare mitosis and cancer.
- Mitosis is controlled cell division by genes for growth and repair
- Cancer is uncontrolled cell division and tumours resulting from mutated and damaged genes.
What is cancer and how does it develop?
- Cancer is uncontrolled cell division and tumours resulting from mutated and damaged genes.
- Most mutated cells die- few that survive cause tumours.
- Uncontrolled division creates a tumour which expands
- Tumour becomes a cancer when it turns from benign (slow growing and doesn’t invade other cells) to malignant (invades surrounding tissue and fast growing)
What the treatments of cancer target and what are they?
- Directed at controlling rate of cell division and killing cells by disrupting cell cycle.
- Chemotherapy- prvents DNA replicating, inhibits metaphase by destroying spindles
- Drugs- stop G1 and enzyme synthesis for DNA replication causing the cell to self destruct.
- Drugs and radiation- damage DNA- cell kills itself and can’t replicate DNA.
How do cancer treatments affect normal cells and how is this mitigated?
- Drugs are more effective if cells divide rapidly.
- As cancer cells divide quicker- more damage done to them than othe rcells.
- Other rapidly dividing cells e.g. hair cells- vulnerable
What safety precaution should be taken with the root tip squash?
Wear safety goggles, a lab coat and gloves.
How to perform the root tip squash experiment?
- Cut 1cm off the root tip- where mitosis occurs- put in boiling tube- add HCl so just covers, put in water bath of 60℃ and leave for 5 minutes.
- Remove tip and rinse with water, leave to dry.
- Place on slide and cut off 2 mm of very tip- use mounted needle to break up and spread thinly.
- Add stain and add coverslip- push down with filter paper- squash don’t smear.
- Place slide on stage and clip in
- Select the lowest magnification objective lens and use the coarse adjustment knob to bring hte stage just below the lens. Look through eyepeice and use coarse adjustment to move the stage down to focuse then focus more with fine adjustment knob.
- Swap to higher magnifications and repeat.
How do you draw a scientific diagram of a cell?
- Use relative size
- Write down magnification and scale
- Single lines and no shading
- Label
- Give title
What is the mitotic index and what is it used for?
- The proportion of cells undergoing mitosis
- Used to work out how quickly a tissue is growing.
What is the formula for the mitotic index?
Number of cells with visible chromasomes/ number of cells observed
Name the process of how bacteria replicate and what does it produce?
- Binary fission
- Produces 2 daughter cells and replicates genetics
Describe binary fission.
- Circular DNA and plasmids replicate. Circular DNA has 2 copies whereas plasmids have many copies
- The copies attatch to the cell membrane at opposite poles.
- The cell membrane and cell get bigger.
- The cell membrane begins to pinch in between the two DNA molecules dividing hte cell in two
- A new cell wall is formed dividing the two original cells into two identical daughter cells with a single identical copy of circular DNA and a variable number of copies of plasmids.
How do viruses replicate?
- As viruses are non living, they do not undergo cell division.
- They attatch to their host cells with attatchment protiens complementary to the receptor protiens on the host cell
- They inject their nucleic acid (DNA or RNA) into the cell.
- The cell then uses its metabolic processes following instructions from the nucleic acid to replicate viral particles to assemble viruses e.g. in ribosomes
- The viruses then burst the cell once enough are made.
Why can viruses only replicate with certain cells and explain the difference between viruses?
- Different viruses require different host cells due to specific attatchment and receptor protiens
- Some viruses can only infect one type of cell
- Other viruses can infect lots of types of cell.
