Cells Flashcards
What is the job of cytoplasm?
Photosynthesis
What is the nuclear envelope?
A double membrane which surrounds the nucleus with nuclear pores helping to maintain the shape and control substances in and out.
3 facts about the vacuole
-holds cell sap
-in plant cell surrounded by the tonoplast a selectively permeable membrane
-Contains mineral salts, sugars amino acids, waste and some anthocyanins
-can act as a temporary food store
-supports turgidity of plants
-pigments may colour petals to attract insects
Give an example of protiens traveling through the Golgi Body.
Mostly hormones like insulin and are put into lysosomes or delivered to membrane bound organelles
What are ribosomes
Smallest and most numerous organelle which is the site of protein synthesis. Has 2 sub units (small and large)
Account for 25% of the dry mass of a cell
What is the Golgi Body?
A series of flattened stacks of membrane vesicles formed by the ER. It modifies and transports proteins out of the cell.
What is the inner membrane of mitochondria?
Space enclosed is called the mitochondrial matrix and contains small circular strand of DN containing genes for some enzymes for aerobic respiration.
Also studded with stale particles which are ATP synthase molecules making ATP during the oxidatve phosphorylation.
Mitochondrial ribosomes to process proteins from the DNA
Enzymes in matrix for Kreb Cycle.
What is the nucleoplasm?
Gelatinous substance inside nuclear envelope which contains chromatin.
What is inside he chloroplast?
membrane bound compartments called thylakoids which are stacked to form grana which are joined by Lamellae. Arrangement of these maximises light catchment. lamellae allow chemicals to move between grana.
Small circular pieces of DNA and ribosomes needed for replication and protein synthesis.
Stroma contain enzymes for photosynthesis
Starch grains/lipid droplets store products of photosynthesis.
Chlorophyll for light absorption of different wavelengths due to different pigments.
What is the smooth endoplasmic reticulum?
A series of interconnected membrane channels.
No ribosomes.
Involved in making lipids for own use.
What are nuclear pores?
Large holes in nuclear membrane that contain proteins of which control the entry and exit of substances from the nucleus.
What are lysosomes?
Small membrane bound vessicles formed by the RER containing hydrolytic enzymes.
What do lysosomes do?
They contain hydrolytic enzymes and digestive enzymes such as protease and have an acid interior.
They are used to break down unwanted chemicals and toxins as well as organelles.
Digested material can be absorbed by cytoplasm, removed via exocytosis to remove unwanted proteins and materials.
Enzymes are released into phagocytic vesicle to leave cell
Performs autolysis on dead cells
What do lysosomes do?
They contain hydrolytic enzymes and digestive enzymes such as protease and have an acid interior.
They are used to break down unwanted chemicals and toxins as well as organelles.
Digested material can be absorbed by cytoplasm, removed via exocytosis to remove unwanted proteins and materials.
What is the Rough Endoplasmic Reticulum?
A series of membrane channels called cisternae which synthesise and transport proteins throughout the cell.
Studded with ribosomes which synthesise proteins which are processed in the RER before being exported via the Golgi Body.
Where are ribosomes found?
Found free in the cytoplasm making proteins from cells own use
Or in RER making proteins to be exported from the cell.
What are ribosomes?
The smallest and most numerous organelle which is the site of protein synthesis.
What is the structure of the mitochondria?
Double membrane structure with an outer and inner membrane.The inner membrane is folded into Christie giving it a larger surface area.
What is the purpose of mitochondria?
Aerobic respiration
ATP synthesis
What is chomatin?
DNA protein complex found in the nucleoplasm. During cel division chromatin becomes condensed into observable chromosomes.
What are plasmodesmata?
Narrow threads of cytoplasm surrounded by cell membrane which connect to the cytoplasm of neighbouring plant cells.
What is the function of the cell wall?
To provide structure from the cell. Also helped via polysaccharide in plants and peptidoglycan in most bacterial cells.
Function of the nucleus?
Stores DNA
What is the process of of proteins entering the Golgi body?
Protiens are fused to the Golgi Body via a incoming vesicle and are then modified (carbohydrate is added to create glycoprotein). It then bud of in a secretory essicle where it uses to the cell membrane and releases content via exocytosis.
How are fungi different from plant cells?
Contain no chloroplasts and cell walls are made of chitcin instead of cellulose.
Differences between eukaryotic and prokaryotic cells?
- much smaller
- structurally smaller
- no nucleus single circular DNA free in the cytoplasm
- smaller ribosomes
What is chromosomal DNA?
- not found in a nucleus
- single circular chromosome called a nucleiod
- always code for something
Cell wall in prokaryotic cells
- made of murine which is made of disaccharides and amino acids
- adds structure and allows materials to be transported
- gram positive and gram negative tests where cell walls absorb a stain. Gram+ means absorb lots so thick cell wall.
Cell membrane in prokaryotic cells.
- phospholipid bilayer plasma membrane lie eukaryotes
- evidence al microorganisms evolved from a single common ancestor
Cytoplasm in prokaryotic cells
- site of all metabollic reactions
- contains microstructures, none are membrane bound
Ribosomes in prokaryotic cells
- float freely
- smaller 70s
Plasmid DNA in prokaryotic cells
- may have one or many
- smaller circular DNA molecule that is separate from chromosomal DNA
- an replicate individually and can be passed between bacteria
Pilli in prokaryotic cells
- thread like structure
-helps bacteria attach to surfaces like host cells membrane and other bacteria
Capsule in prokaryotic cells
-surrounds the cell wall, gelatinous structure made of polysaccharides
-prevents bacteria from being ingested by phagocytes and adhere to surfaces
-provide protection- e.g present of one is linked to virulence - the ability to cause disease
Flagella
-can have one or some
-composed of protein called flagellin
-used for movement
Steps for Binary Fission of prokaryotes
1)DNA and plasmids replicate, plasmids can be replicated many times
2) cell elongates and DNA moves to opposite poles of the cell
3) cytoplasm divides and new cell wall begins to form
4) cytoplasm divides to produce daughter cells each contain identical DNA loop but can contain different amounts of plasmid copies.
Structure of the virus
-neither pro/eukaryotic
-they are acellular non-living particles
-1000x smaller than bacteria
-consist of genetic material (RNA), protected by a protein coat (capsid)
-may also have a lipid envelope
- the capsid/lipid envelope will have attachment proteins/antigens to help recognise hosts.
What is cell fractionation
- used to obtain large numbers of isolated organelles
- cells are broken and individual organelle separated
Preparation for cell fractionation
Tissue placed in cold,buffered solution of the same water potential of the tissue.
1) cold to reduce enzyme activity
2) buffered to avoid pH fluctuation
3) same water potential to reduce chance of lysis via osmosis
Step 1 (cell fractionation)
Homogenation
- cells broken up by homogeniser a blender releasing organelles from the cell
Step 2 (cell fractionation)
Filtration
-homogenate is filtered to remove complete cells and large debris such as cell membranes.
Step 3 (cell fractionation)
Ultracentrafusion
1) tube of filtrate spun at a slow speed
2) heaviest organelles (nuclei) will be forced to the bottom to form a pellet
3) supernatant is removed leaving the nuclei sediment
4) supernatant added to another tube and spun at a higher speed
5) process is repeated as organelles separate from heaviest to lightest increasing the spin speed each time
Order of organelle separation (cell fractionation)
-nuclei
-chloroplasts
-mitochondria
-lysosomes
-endoplasmic reticulum
-ribosomes
What is magnification?
Making the image appear larger than the object
What is resolution?
The ability to determine between to different points (same as resolving power)
Total magnification=
Eye peice lens x objective lens
Image size =
Actual size x magnification
Steps to preparing a slide
1) add water (stops dehydration)
2) add a thin section of plant tissue (so light can pass through)
3) stain with iodine (to create a contrast between organelles)
4) lower coverslip at an angle using a mounting needle (to avoid air bubbles)
Light microscopes
- use a lens to project a magnified image of an object onto the eye
- limited magnification of 1500x
- long wave length of light means that microscope can only distinguish between 2 objects if they are 0.2um or further apart.
Electron microscopes (TEM and SEM)
- exposes specimens to electrons
-takes place in a vacuum so specimens are dead
-much shorter wavelength so produce images of greater resolution (up to 0.1nm)
-magnification of up to 2x10 power of 6
-smaller objects seen clearer e.g ribosomes
Scanning electron microscope
-specimen coated with a thin layer of metal like gold,platinum or tungsten to improve conductivity and contrast.
-electrons are reflected from the surface of the specimen creating a 3D image
-whole cells and tissues can be imaged
-colour is computerised
Transmission electron microscopes
-very thin slice which is stained with a heavy metal
-electrons do not pass through heavily stained parts because they are absorbed
- those that pass through are focused by electromagnets onto fluorescent screen
-allows us to see clear 2D cross sections of cells
How are phospholipids arranged in double membrane bilayer?
They arranged so that their hydrophilic heads are facing outward and their hydrophobic tails face inwards.
What do the phospholipids do?
- separate organelles from the cytoplasm so specific metabolic reactions can take place
- creates a concentration gradient important for mitochondria in ETC
- controls the entry and exit of materials
-provides internal support (ER) - isolates enzymes which may damage the cell (lysosomes)
- provide surfaces for reaction
-forms a barrier to large polar molecules and ions as well as water soluble substances. - allows lipid soluble substances to enter/leave
-makes membrane flexible and self sealing
What is the fluid mosaic model?
Phospholipids can move relative to one another giving the membrane a flexible structure.(fluid) Proteins embedded in bilayer give mosaic appearance
What is an entrisic protein?
-interspersed through out membrane
-only span part of membrane
-act as a mechanical support or as cell receptors
What is an intrinsic protein?
- span entire membrane
-involved in the transport of materials
-channel and carrier proteins
What does a channel protein do?
Form water filled tubes to allow soluble ions to diffuse across the membrane
What does a carrier protein do?
Binds ions or molecules like glucose/amino acids and changes shape to transport them across the membrane
What is a glycoprotein and its function?
-Protein with a carbohydrate attached which sticks out of the membrane
-acts as a cell surface receptor for hormones
- at as antigens (e.g lymphocytes)
-can help cells attach to one another in order to form tissues (cell adhesion)
What is the function of a glycolipid?
-phospholipid with a carbohydrate chain (covalent bond) which sticks out
-site for cell signaling (receptors for hormones)
- act as antigens and help hold cells together
Cholesterol
-found in the bilayer between phospholipids and or proteins
- add strength to membrane by reducing lateral movement and making the membrane less fluid at high temperatures
- very hydrophobic so prevent leakage of water and dissolved ions from the cell
What is the nucleolus?
Found in the nucleus and it and manufactures rRNA and ribosomes
What does the Golgi body do?
- modifies proteins by adding carbohydrates to form glycoproteins
- produces secretory enzymes
- secretes carbs
- transports modifies and stores lipids
- forms lysosomes
Cell wall in plants
-consists of microfibrils of cellulose embedded in a matrix
- thin layer called middle Lamellae which marks boundary between adjacent cells and cements them together
-provides mechanical strength against osmosis
-allows water to pass along it
-made of cellulose in algae
-made of chitin in fungi
How is DNA in the chloroplasts different to DNA in the nucleus
-circular
-shorter
Why might organelles not be visible in the cytoplasm of a red blood cell?
The cytoplasm is filled with haemoglobin
