Cells Flashcards
How do antiporters work?
Two molecules are transported at the same time in opposite directions. One of the molecules is travelling down the concentration gradient, and the anti porter harnesses and uses this energy to transport the other molecule against the concentration gradient
How does a scanning electron microscope work?
A section of the specimen is taken and stained with heavy metals. It is then placed into a vacuum, and an electron beam is bounced off of the surface of the object, enabling 3D images to be created.
What are four ways to increase rate of diffusion?
- increase temperature
- increase surface area
- increase difference in concentration
- thin exchange surface
How do prokaryotic cells differ from eukaryotic cells?
Prokaryotic cells have :
- smaller ribosomes
- no nucleus
- a cell wall with murrain
- single circular loop of DNA
- plasmids
- capsule surrounding the cell
- flagella
What are the two types of co-transport?
Antiport - two molecules in opposite directions at the same time
Symport - two molecules in the same direction at the same time
State the main features and functions of the cell vacuole
Features - can take up most of the space in a plant cell
Functions - maintains water balance in the cell and provides structure
State the main features and functions of the mitochondria
Features - sausage shaped organelle that is surrounded by two membrane layers, the inner of which folds in to form the crustal
Functions - produces ATP during aerobic respiration
What are the three states of tonicity with regards to water potential?
Hypotonic - higher water potential outside the cell, so water moves into the cell
Isotonic - equal water potential, so no net movement of water
Hypertonic - lower water potential outside the cell, so water moves out of the cell
What is facilitated diffusion?
The passive movement of molecules from a high concentration to a low concentration using carrier or channel proteins.
What happens in telophase?
Seperated chromosomes collect, and a nuclear envelope forms around them
What are the three main roles of cholesterol in the phospholipid membrane?
- increasing structure and stability
- reducing changes in fluidity when temperature varies. Without it, the membrane would go very fluid when its warm and very rigid when its cold
- filling in empty space to prevent water-soluble molecules passing in and out of the cell easily
State the main features and functions of the RER
Features - made of membranes that from a series of tubes, and covered in ribosomes
Functions - synthesises and transports proteins
What is simple diffusion?
Movement of particles from a high concentration to a low concentration across the membrane without any assistance from transport proteins. Very small non-polar molecules and lipid soluble molecules can travel freely across the phospholipid bilayer.
How do symporters work?
Two molecules are transported in the same direction. One is moving down the concentration gradient, and this pulls the other molecule, providing it with the energy to move against the concentration gradient.
What happens in anaphase?
Spindle fibres shorten, pulling the chromosomes to opposite sides of the cell
What is osmosis?
The net movement of water molecules across a membrane from a higher water potential to a lower water potential.
What is the definition of magnification and resolution?
Magnification - making things larger
Resolution - distinguishing between objects that are close together
State the main features and functions of the cell surface membrane
Features - found around edge of the cell and made up of lipids and proteins in a phospholipid bilayer
Functions - controls movement of substances in and out of the cell
State the main features and functions of the ribosomes
Features - very small organelle that is not surrounded by a membrane
Functions - assembles protein molecules from the separate amino acids
How do channel proteins work?
Channel proteins span the entire width of the membrane, and have a water filled centre. This allows water soluble ions and molecules to pass through.
What happens in cytokinesis?
Cytoplasm divides to form two new cells
What is the difference between eukaryotic and prokaryotic cells?
Eukaryotic cells are found in plants, animals and fungi and contain a nucleus. Prokaryotic cells include bacterial cells and do not contain a nucleus
Describe the steps involved in cell fractionation and ultracentrifugation
1) cells are broken down in a homogeniser. The tissue is then suspended in a buffer solution to keep the pH constant, and kept cold
2) Mixture is filtered to remove large pieces of tissue
3) Tubes placed into a centrifuge, and spun. Heavier organelles fall to the bottom of the tube.
4) This process is repeated, with smaller organelles being separated off at higher speeds
State the main features and functions of the nucleus
Features - largest organelle in the cell and surrounded by a bilayer membrane called the nuclear envelope. Substances enter and exit through nuclear pores. Inside the nucleus is a nucleolus, where rRNA is assembled into ribosomes
Functions - contains the DNA of the cell
State the main features and functions of the chloroplasts
Features - large organelles with three membranes that contain chlorophyll embedded in disc shaped structures
Functions - contains chlorophyll which produce energy through light absorption
What happens in metaphase?
Spindle fibres attach to each chromosome, and they line up in the centre
How is energy released from the ATP?
ATP is hydrolysed down into ADP and a phosphate molecule - this releases energy
What lipid forms the basis for membranes in and around cells?
Phospholipids
Why can cholesterol and phospholipids interact?
They both have a hydrophilic, polar head and the rest of the molecule is hydrophobic and non polar. This enables them to interact with each other.
What is the fluid mosaic model?
A model used by scientists to describe the cell membrane. Fluid because the phospholipids can move around a little in the membrane, and mosaic because the proteins are dotted throughout, similar to the tiles in a mosaic.
What is the arrangement of phospholipids in the cell surface membrane?
Two rows of phospholipids arranged with their hydrophilic heads facing outwards and the hydrophobic tails pointed inwards
What is the highest value of water potential?
0, and is found in pure water. All other solutions have a negative water potential.
State the main features and functions of the lysosomes
Features - contains digestive enzymes in lysozymes, which is then separated from the rest of the cell by a membrane surrounding the lysosome
Functions - digests unwanted material in the cell
What happens in prophase?
Chromosomes coil and become shorter and fatter. Nuclear envelope disappears and protein fibres form a spindle in the cell.
What is the basic structure of a virus?
Around 50x smaller than bacteria, and don’t have a cellular structure like living organisms do. They can only replicate inside a living cell, and have core genetic material. Surrounding this genetic material, there is a protein coat called a capsid, which protects it.
How do carrier proteins work?
Carrier proteins span the entire membrane width, and have a binding site on their surface. This only binds to one specific molecule. When they bind to the molecule, the protein changes shape, causing the protein to carry the molecule through into the cell.
What is mitosis?
The part of the cell cycle where a eukaryotic cell divides to form two identical daughter cells
What happens in interphase?
Cells make a copy of the chromosomes, replicating the DNA
What are the basic steps in the root tip squash mitosis practical?
1) heat acid for around 5 mins in a water bath, and then place the root tip into the vial
2) After the root tips have had a chance to heat and soften, gently rinse them with distilled water and blot them dry
3) Stain them using acetic orcein, and once the cells have absorbed it, carefully dilute the excess stain off
4) Place the root tips on a microscope slide, and place a coverslip on top. Carefully but firmly press down, squashing the cells to a singular layer
State the main features and functions of the SER
Features - made of membranes that form a series of tubes (same as the RER) but completely smooth
Functions - synthesises lipids
State the main features and functions of the Golgi apparatus and vesicles
Features - stack of flattened sacks, which the vesicles are pinched off of
Functions - processes then packages molecules to use in other parts of the cell or to be exported out of the cell. Also forms lysosomes.
Where are glycoproteins and glycolipids found in the cell membrane, and what is their function?
They are found on the surface of the cell membrane, are made up of a polysaccharide attaching to a protein or lipid, and act as receptors for hormones and play an important role in cell recognition
State the main features and functions of the cell wall
Features - fairly thin but very strong wall that resists being stretched
Functions - very strong to prevent the cell from bursting and gives structure to the stems
How do transmission electron microscopes work?
A very thin specimen is taken and preserved and stained with heavy metals. It’s then placed into a vacuum, and a beam of electrons are fired through. The electrons pass through the areas strained with heavy metals less easily, providing a contrast on the image.
What is active transport?
Movement of substances against the concentration gradient, requiring ATP.
Which organelle digests bacteria?
Lysosomes - membrane bound vesicle which contains lysozymes that digest unwanted material
