Cells Flashcards
What are the organelles in an animal cell?
Cell membrane
Rough endoplasmic reticulum
Smooth endoplasmic reticulum
Lysosome
Ribosome
Nucleus
Golgi apparatus
Golgi vesicle
Cytoplasm
Mitochondria
What are the organelles in a plant cell?
Cell surface membrane
Chloroplast
Rough Endoplasmic reticulum
Mitochondria
Golgi apparatus
Golgi vesicle
Vacuole
Smooth endoplasmic reticulum
Cytoplasm
Nucleus
Ribosome
Cell wall
What is the description and function of the lysosome ?
D:-bags of digestive enzymes
It’s a type of Golgi vesicle.
F:-Contains digestive enzymes called lysozymes which can be used to hydrolyse pathogens and old cell organelles
What is the description and function of the ribosome?
D:- A very small organelle that floats free in the cytoplasm or is attached to the RER. It is made up of proteins and RNA. It’s not surrounded by a membrane.
F:-The site where proteins are made
What is the description and function of the cell wall?
Strong, structured wall that supports the cell and prevents it from changing shape
Plants/Algae>made from cellulose
Fungi >made from chitin
What are the components of the ultrastructure of the nucleus?
nuclear envelope
nuclear pores
nucleoplasm
nucleolus
chromatin
what are the functions of the components of the ultrastructure of the nucleus
nuclear envelope-double membrane that controls entry and exit of materials. continuous with RER
nuclear pores- allow mRNA/ribosomes to exit the nucleus
nucleoplasm-jelly like material;makes up bulk of nucleus
nucleolus- contains rRNA and makes ribosomes
chromatin-uncondensed complex of dna/proteins
what are the components of the ultrastructure of the mitochondria
Cristae(inner membrane)
Matrix(fluid centre)
outer membrane
What are the functions of the components of the ultrastructure of the mitochondria
Mitochondria are the sites of ATP production via aerobic respiration
DNA codes for enzymes needed in respiration
What are the components of the ultrastructure of chloroplasts
chloroplast envelope
thylakoids
grana
stroma
lamellae
starch grain
double membrane
what are the functions of the components of the ultrastructure of the chloroplasts
chloroplasts are the organelles that carry out photosynthesis
chloroplast envelope:a partially permeable double membrane
thylakoids:flattened sacs that contain the pigment chlorophyll
grana:stacks of thylakoids- where 1st stage of photosynthesis takes place
stroma:fluid filled matrix where 2nd stage take place
How are chloroplasts adapted to carry out their function
Granal membranes provide a large surface area for photosynthesis
the stroma contain enzymes for sugar synthesis
chloroplasts contain DNA and ribosomes so can quickly manufacture proteins required for photosynthesis
What are the components of the ultrastructure of the RER?
cisternae (folded membranes)
studded with ribosomes
What is the function of the components of the ultrastructure of the RER?
usually attached to the nucleus
folds and processes proteins that have been made at the ribosomes
What is the golgi apparatus?
stack of flattened membranes that form sacs
accepts and produces vesicles
sorts and labels proteins and lipids so they are sent to the correct destination
make lysosomes
What are the functions of the golgi apparatus
transport and modify stored lipids
forms lysosomes
produces secretory enzymes
secretes carbs for cell walls
processes and packages new proteins and lipids
What are the functions of the golgi apparatus
Adds carbohydrates to proteins to make glycoproteins
transport and modify stored lipids
forms lysosomes
produces secretory enzymes
secretes carbs for cell walls
What is the SER?
cisternae(folded membranes)
not studded with ribosomes
What are the functions of the SER?
synthesises and stores carbohydrates and lipids
What is the function of the vacuole
makes plant cells turgid; adding to support
sugars and amino acids act as temporary food store
pigment used to colour petals to attract pollinating insects
not attached to the nucleus
How big are 80S ribosomes and where are they found
25nm
eukaryotes
how big are 70s ribosomes and where are they found
20nm
prokaryotes, mitochondria, chloroplasts
What is the function of the golgi vesicle?
stores lipids and proteins made by the golgi apparatus and transports them out of the cell
What is the only organelle that doesn’t have a membrane
ribosomes
Which organelle has a double membrane
The bigger membranes
The Nucleus,
Mitochondria,
Chloroplasts
What properties do molecules have to have in order to be able to cross the phospholipid bilayer?
they have to be lipid soluble/ non polar and they have to be small
things like steroids, oxygen and CO2 can pass through
Why do phospholipids have a proteins on them
To allow water soluble molecules to pass through
Some of the proteins are intrinsic and some are extrinsic
What is the tile/mosaic effect
The effect that the random arrangement of the proteins have on the organised phospholipids
How do intrinsic proteins work on a phospholipid ?
They pass right through the phospholipid bilayer and have hydrophobic amino acids on the surface on the protein. The hydrophobic amino acids can interact with the hydrophobic fatty acid tails in the phospholipid bilayer
What is an intrinsic protein channel
These contain a channel running through the centre. The channel is lined with hydrophilic amino acids and is filled with water molecules. Protein channels allow water soluble molecules and ions to diffuse through
What is a intrinsic protein carrier
They can change shape or position to transfer molecules or ions from one side of the membrane to the other
How do extrinsic proteins work on a phospholipid ?
They don’t span the membrane, unlike intrinsic proteins. Instead, they are found on one side of the membrane or the other. Sometimes extrinsic proteins are attached to intrinsic proteins.
They have a range of functions
Give 3 examples of specialised cells and how they are adapted for their function
-epithelial (have villi, microvilli
and mitochondria)
-RBC(no nucleus)
-sperm(lots of mitochondria)
Specialised cells are grouped together to form?…
tissues
What is a tissue
a group of cells working together to perform a particular function
Different tissues work together to form?…
organs
Different organs make up an..?
organ system
What is the difference between a prokaryotic cell and a eukaryotic cell?
Prokaryotic cells are much smaller and simpler than eukaryotic cells-and they don’t have any membrane-bound organelles (like a nucleus) in their cytoplasm.
What do prokaryotic cells contain?
cytoplasm
70S ribosomes
cell wall
cell surface membrane
flagellum
circular DNA
plasmids
capsule
What is the function of the cell surface membrane and what’s it made of?
-mostly made of lipids and proteins
-controls the movement of substances in and out of the cell
What is the function of the cell wall and what’s it made of?
-supports the cell and prevents it from changing shape
-murein
What is the function of the capsule and what’s it made of?
-made of secreted slime
-its helps to protect the bacteria from attack by cells of the immune system
What is the function of plasmids?
small loops of DNA that can be passed between oases between prokaryotes and contain genes for things like antibiotic resistance
What is the function of the flagellum?
Long, hairlike structure that rotates to make the prokaryotic cell move
what is binary fission?
the process by which prokaryotic cells use to replicate themselves
What is the process of binary fission?
1) circular DNA and plasmid(s) replicate. the main DNA loop is only replicated once but plasmids can be replicated loads of times.
2) the cell gets bigger and the DNA loops move to opposite ‘poles’ of the cell
3) the cytoplasm begins to divide (and new cell walls begin to form)
4) the cytoplasm divides and 2 daughter cells are produced, each daughter cell has one copy of circular DNA, but can have a variable number of copies of the plasmid(s)
what are viruses?
nucleic acid, surrounded by protein. they’re not cells, they’re not alive
How do viruses work?
they invade and reproduce inside the cells of other organisms
what are the cells that viruses invade known as?
host cells
What is the basic structure of a virus ?
they have no cell surface membrane, no cytoplasm and no ribosomes
-they have a code of genetic material(either DNA or RNA)
-a capsid
-attachment proteins
what is a capsid?
a protein coat
What are the steps of a viral replication
1.virus attaches to host cell receptor proteins
2.genetic material is released into the host cell
3.genetic material and proteins are replicated by host cell ‘machinery’
4.viral components assemble
5.replicated viruses released from host cell
How do virus attach themselves to host cell receptor proteins?
They use their attachment proteins to bind to complementary receptor proteins on the cell-surface membrane of the host cell surface
What do we mean by ‘complementary receptor proteins’?
Different viruses have different attachment proteins and therefore require different receptor proteins on host cells. As a result, some viruses can only infect one type of cell
What is the magnification calculation formula?
magnification=image size/actual size
What is the magnification calculation formula?
magnification=image size/actual size
how do you calculate m>mm>um>nm
x 1000 for each
What is magnification?
the degree to which the size of an image is larger than the object itself ( specimen. )
What is resolution?
the degree to which it is possible to distinguish between (two) objects that are close together (see as separate objects).
What is the difference between a light microscope and an electron microscope regarding wave length
light microscopes have a long WL and electron microscopes have a short WL
In terms of magnification, how does an optical microscope and electron microscope compare?
optical microscope has a lower magnification
optical (maximum of x1500)
higher (maximum of x 1500000)
In terms of resolution , how does an optical microscope and electron microscope compare?
optical microscope has a lower resolution
optical (maximum of 0.2um)
higher (maximum of 0.0002um)
What is the difference between a TEM and SEM?
TEMs have a higher resolution than SEMs
The image from SEMs can be 3D
What are the advantages and disadvantages of TEMs?
+give high resolution images so shows small objects
-can only be used on thin specimens
-can only view specimens in a vacuum so can only be used on non-living specimens
What are the advantages and disadvantages of SEMs?
+can be used on thick specimens
+can be 3D
-give lower resolution images than TEMs
-can only be used on non living specimens
how do you prepare a microscope side?
- pipette a small drop of water onto the centre of the slide
- Use tweezers to place a thin section of your specimen on top of the water drop.
- Add a drop of a stain
- Add the cover slip(try not to get any air bubbles or they’ll obstruct your view of the specimen)
What are microscope artefacts?
things that you can see down the microscope that aren’t part of the cell or specimen that you’re looking at e.g air bubbles, fingerprints, dust
Artefacts are usually made during the preparation of your specimen and shouldn’t really be there at all.
what are the 3 steps of cell fractionation?
1.homogenisation(breaking up the cells)
2.filtration(getting rid of the big bits)
3.ultracentrifugation(separating the organelles)
What are some ways that homogenisation can be done and what do they do?
vibrating the cells or grinding them up in a blender. this breaks up the plasma membrane and releases the organelles into solution
What are the conditions needed for homogenisation to occur?
the solution must be kept ice cold(to reduce the activity of enzymes that break down organelles), it must be isotonic(prevents damage to the cells through osmosis) and a pH buffer must be added(to maintain pH)
What is done during cell filtration and why does this happen?
It’s filtered through a gauze to separate any large cell debris or tissue debris from the organelles. The organelles are much smaller than the debris, so they pass through the gauze
Why do we use ultracentrifugation?
After filtration, you’re left with a solution containing a mixture of organelles. To separate a particular organelle from all the others you use ultracentrifugation
How does ultracentrifugation happen?
The cell fragments and poured into a tube. The tube is put into a centrifuge and is spun at a low speed. The heaviest organelles get flung to the bottom of the tube by the centrifuge and form a thick sediment at the bottom(the pellet). The rest of the organelles stay suspended in the fluid above the sediment (the supernatent)
The supernatant is drained off, poured into another tube, and spun in the centrifuge at a higher speed. Again, the heaviest organelles form a pellet at the bottom of the tube. This process is repeated at higher and higher speeds, until all the botone les are separated out
What are the 2 parts of the cell cycle
interphase(cell growth)
mitosis
What are the 3 growth stages of interphase?
G1, S, G2
what happens during G1
cell grows and new organelles and proteins are made
What happens during S
cell replicates its DNA, ready to divide by mitosis
what happens during G2
cell keeps growing
and proteins
needed for cell division are made
What are the 4 phases of the chromosome structures in mitosis
PMAT
prophase
metaphase
anaphase
telophase
What are the 4 phases of the chromosome structures in mitosis
PMAT
prophase
metaphase
anaphase
telophase
what happens during the prophase stage
The chromosomes condense, getting shorter and fatter.
Tiny bundles of protein called centrioles start moving to opposite ends of the cell, forming a network of protein fibres across it called the spindle.
what happens during the metaphase stage
The chromosomes (each with two chromatids) line up along the middle of the cell and become attached to the spindle by their centromere.
what happens during the anaphase stage
The centromeres divide, separating each pair of sister chromatids.
The spindles contract, pulling chromatids to opposite poles (ends) of the spindle, centromere first. This makes the chromatids appear v-shaped.
what happens during the telophase stage
The chromatids reach the opposite poles on the spindle. They uncoil and become long and thin again. They’re now called chromosomes again. A nuclear envelope forms around each group of chromosomes, so there are now two nuclei.
describe how you would use a microscope to find the diameter of X(e.g. triglyceride droplets) on a slide
calibrate the eyepiece graticule by using the stage micrometer
measure the length of the diameter or X(triglyceride droplets)
repeat the measurements and calculate a mean
why is DNA replication known as self conservative replication
because each new DNA molecule contains one old and one new strand
what happens during self conservative replication
-helicase enzyme unzips DNA double helix
-tree nucleotide bases match up to complementary bases on old strands
-DNA polymerase enzyme joins nucleotides together
-enzyme rewinds DNA into double helix
-two copies of original DNA
why does cancer happen?
A factor causes the interphase section of the cell cycle to be shortened leading to rapid growth of cells
This leads to uncontrolled growth which produces a tumour
how can we treat cancer?
Preventing DNA from replicating
Inhibiting the metaphase stage of mitosis
What is a plasma membrane?
A phospholipid membrane that surrounds a cell or its organelles.
Give an example of a plasma membrane and name its function
The cell surface membrane.
Its function is to:
-separate the cytoplasm from the external environment of a cell
-control what can enter and exit the cell
What are phospholipids described as and why?
They are amphipathic as they have polar and non polar regions. They have a polar head which is hydrophilic and non polar fatty acid tails which are hydrophobic
What is the function of the phospholipid bilayer?
-allow lipid soluble molecules to move through such as lipid based hormones (steroids) and gases
-prevent water soluble molecules from entering such as glucose ions.
-make the membrane flexible and self sealing.
Where are proteins found in the cell surface membrane?
They are interspersed throughout the membrane
What is the function of intrinsic proteins?
Span the cell membrane
Where are extrinsic proteins found and what is the function?
They occur on the surface of the phospholipid bilayer.
They can be stand alone proteins and sometimes they associate with carbohydrates to form glycoproteins
What is the function of glycoproteins?
-cell recognition (antigens)
-Help cells attach to one another and form tissues (mechanical strength)
-form receptor sites for hormones or neurotransmitters.
What are glycolipids?
They are carbohydrates covalently bonded to lipids.
They extend from the phospholipid bilayer.
What are the functions of glycolipids?
-cell recognition (antigens)
-help cells attach to one another and form tissues (mechanical strength)
What is cholesterol?
It is a type of lipid (so its hydrophobic).
Cholesterol pulls together the fatty acid tails of phospholipids
What are the functions of cholesterol?
-Reduces lateral movement of phospholipids and other molecules.
-Acts as a buffer to temperature changes, so maintains membrane fluidity.
-Prevents water and ion leakage.
ET: Explain why phospholipids form a bilayer in plasma membranes
ET: How can polar and non-polar molecules pass through the membrane?
ET: Other than as carrier proteins, state two functions of membrane bound proteins
-Receptors
-Enzymes
-Structural
ET: Explain why the model for membrane structure is known as the fluid mosaic model
ET: Describe the structure and function of the glycoproteins/lipids
What properties do molecules have to have in order to be able to cross the phospholipid bilayer?
-lipid soluble/non polar
-small
-steroids/ oxygen/ carbon dioxide
What molecules cannot cross the phospholipid bilayer?
-water soluble/ polar
-large molecules
-glucose/amino acids
What is simple diffusion?
It is the passive net movement of molecules from an area of high concentration to an area of low concentration until evenly distributed
what are the features of simple diffusion?
- a passive process no ATP involved)
- small non-polar molecules e.g. oxygen, carbon dioxide, lipid-based hormones (steroids).
- no carrier proteins involved.
Give examples of where diffusion occurs
-In the lungs (alveoli to blood, blood to alveoli)
-Small intestine
-Lumen to blood
-Leaves of a plant
Why does diffusion occur?
So that materials/substances can be exchanges between cells and their environment
Explain why diffusion is referred to as a passive process?
The energy that the particles that are moving possess comes from their ‘natural’ inbuilt motion rather than an external source
What are the 4 factors that affect diffusion?
-concentration gradient
-distance diffusion is taking place over
-thickness of the exchange surface
-temperature
How does concentration gradient affect the rate of diffusion
How does surface area affect the rate of diffusion?
As the surface area increases the rate of diffusion increases as a larger surface area provides more space for the particles to move across
How does thickness of the exchange surface affect the rate of reaction
A thinner exchange surface means a shorter diffusion pathway so particles can diffuse more quickly. This increases the rate of diffusion.
How does temperature affect the rate of diffusion?
At higher temperatures, particles gain more kinetic energy. This causes them to move faster, increasing the rate of diffusion as particles collide with the exchange surface more frequently and with greater force.
What is Flick’s Law?
What is facilitated diffusion?
How is facilitated diffusion different from ‘simple’ diffusion?
Facilitated diffusion can only occur at specific points in the plasma membrane where there are specific protein molecules and it transports large, charged ions or polar molecules across the membrane
What are the two types of protein molecules?
- channel protein
- carrier protein
How is a channel protein formed and what is the function?
Some proteins form water- filled hydrophilic channels across the membrane and allow water soluble molecules to cross (e.g. water soluble ions).
These channels are specific/selective and will only allow certain molecules to cross- therefore the channel will remain closed if the molecule is not there, it only opens if ion present
The ion will bind- causing protein channel to change shape and the channel will then open
What is she function of a carrier protein?
When specific molecules e.g glucose is present it binds specifically to the carrier protein. This causes the carrier to change shape allowing the molecule to cross the plasma membrane where there
How can large and polar molecules enter the cell?
By facilitated diffusion form their concentration gradient with the aid of proteins
What is osmosis?
Osmosis is the passive movement of water molecules from an area of high water potential to an area of low water potential through a partially permeable membrane
How is osmosis different to normal diffusion?
Osmosis involves water molecules whilst diffusion involves molecules and ions. Osmosis is from a high water concentration to low water concentration whilst diffusion is from a high to low concentration
What is a solute?
Any substance that is dissolved into a solvent
What is a solvent?
The liquid that the solute is dissolved into a
What is a solution?
Solute and solvent together
Explain the practical on identifying the wager potential of plant tissue
-cut chips with potato cutter in uniform width and uniform length (2-3cm)
-the peel should be removed from each end as it acts as a barrier and does not have the same permeability as the inner tissue.
-put the individual chips on a paper towel with the NaCl concentration written on it
-weigh the individual chips using a mass balance and record the mass.
-put the chips in the corresponding NaCl concentration as labelled on boiling tube for 15 minutes.
-after 15 minutes remove chips from the solutions and blot dry to remove excess liquid so that it isn’t recorded in the final mass and doesn’t lead to inaccurate results
What is water potential?
It is how freely water molecules can move
It is measured in kilopascals (kPa)
Pure water has a water potential of 0 because it can move freely
What happens when u add a solute to water?
You lower its water potential because it water molecules are attracted to the solute- they are less free to move around.
In which direction does water move during osmosis?
Water molecules move from the solution with the higher water potential to the one with the lower water potential until the two are equal. This causes the level of water to change
What does isotonic mean?
It refers to solutions separated by a partially permeable membrane that have the same solute concentration and water potential. Osmosis will not occur.
What does hypotonic mean?
Refers to a solution that contains a low solute concentration
What does hypertonic mean?
Refers to a solution that contains a high solute concentration
How do plant cells react to osmosis?
The water potential outside eve cell is the same as the water potential inside the cell
There is no net movement of water
So the water potential outside the cell is isotonic
How do animal cells react to osmosis?
The water potential outside the cell is lower than the cell cytoplasm. Water has therefore moved oht or the cell.
The cell become crenated as the cytoplasm pulls away from the cell membrane.
The water potential outside the cell is hypertonic.
What happens once water molecules have moved from high WP to low WP and there is an equal number of water particles(no net movement)?
Dynamic equilibrium has been reached
What happens if you place a RBC in pure water?
Animal cell will eventually burst (it is haemolysed)
Plant cells- swelling cytoplasm and vacuole will push against the cell wall which will stop the cell wall getting any larger (turgid)
What happens if you place a RBC in concentrated sugar?
-animal cell: cell contents shrink and membrane wrinkles- crenated
-plant cell- cytoplasm and vacuole shrink and plasma membrane pulls away from cell wall- PLASMOLYSIS/FLACCID
What is the difference between hypotonic and hypertonic solution?
Hypotonic has MORE water (solvent) and less solute.
Hypertonic has less water (solvent) and MORE solute
