Cells Flashcards
1
Q
What is a eukaryotic cell?
A
A cell with a distinct nucleus and membrane bound organelles
2
Q
What is a eukaryote?
A
A whole organism made of eukaryotic cells.
3
Q
What is the function of a nucleus?
A
Managing the cell’s genetic material.
4
Q
What is the function of the mitochondrion?
A
Produce energy through cellular respiration.
5
Q
What is the function of ribosomes?
A
Protein-synthesis.
6
Q
What is the structure of a nucleus?
A
Nuclear envelope, double membrane, helps control what goes in/out of the nucleus.
Nucleoplasm
Nucleolus, where ribosomes are made
Chromosomes, coils round proteins called histone proteins which are together called chromatin.
Nuclear pores, allow things like RNA to leave the nucleus
7
Q
What is the structure of the mitochondrion?
A
Matrix, enzymes and proteins needed for respiration
Double membrane, controls what goes into and out of the mitochondria
Cristae, fold around and create the matrix, increases more surface area for enzymes involved in ATP.
8
Q
What is the function of the chloroplasts?
A
Synthesise food by the process of photosynthesis
9
Q
What is the structure of the chloroplasts?
A
Surrounded by a double membrane which contains thylakoids, folded membrane embedded with pigments
Fluid filled stroma contains enzymes for photosynthesis
Found in plants
Grana, where the first stage of photosynthesis takes place
Lamelle, connects the grana together
10
Q
What is the function of the Golgi apparatus?
A
Helps process and package proteins and lipid molecules
Forms glycoproteins and lysosomes
11
Q
What is the structure of the Golgi apparatus?
A
Fluid filled membrane sacs
Small rounded hollow vesicles
12
Q
What is the function of the lysosomes?
A
Digests invading cells and breaks down worn out parts of cells
13
Q
What is the structure of the lysosomes?
A
Contains hydrolytic enzymes
Enzymes surrounded by membrane
14
Q
What is the structure of ribosomes?
A
Loose in cytoplasm or attached to rough endoplasmic reticulum
Made of protein and RNA
80s ribosomes, slightly bigger than prokaryotic
Very small
15
Q
What is the function of the rough endoplasmic reticulum?
A
Folds and packages proteins and sends them to Golgi apparatus
Provides a pathway for the transport of proteins throughout the cell
16
Q
What is the structure of the rough endoplasmic reticulum?
A
Has ribosomes on the outer surface of membranes
Sheet like membranes
17
Q
What is the function of the smooth endoplasmic reticulum?
A
To synthesise, store and transport lipids and carbohydrates
Packages molecules and sends them to the Golgi apparatus
18
Q
What is the structure of the smooth endoplasmic reticulum?
A
Does not have ribosomes
19
Q
What is the function of the cell wall?
A
Supports the cell, provides strength and prevents lysis/ change of shape
20
Q
What is the structure of the cell wall?
A
Made out of cellulose in plant and algal cells
Made out of chitin in fungi
Consists of a number of polysaccharides
21
Q
What is the function of the cell vacuole?
A
Store nutrients and water on which a call can rely for its survival
Isolates unwanted chemicals inside the vell
Maintains pressure inside the cell
22
Q
What is the structure of the cell vacuole?
A
Contains cell sap, weak solution of sugar and salts
Surrounding membrane called tonoplast
23
Q
What is the structure of the bacterial cell?
A
Cell membrane
Circular DNA
Cell wall- made out of murein, strengthen and support, prevent osmotic lysis
Plasmids- genes for antibiotic resistance
Cytoplasm
Capsule- mucilaginous slime layer
Flagellum
Ribosomes
Some chlorophyll associated with cell membrane
24
Q
What is the structure of a virus?
A
Attachment proteins, identify and bind to suitable host cells.
Capsule, protein
Genetic material (RNA) , nucleic acid
Lipid envelope, some but not all
Acellular
Non-living, can’t reproduce by themselves, need a host cell
20-300nm, smaller than prokaryotic cells
25
What is the formula for magnification?
Image size/ actual size
26
What is the formula for image size?
Actual size x magnification
27
What is the formula for actual size?
Image size/ magnification
28
Millimetre to micrometer?
X 1000
29
Micrometer to nanometer?
X 1000
30
Properties of light microscopes?
Magnification?
Resolution?
-light forms an image
-lenses magnify the image
-without light, no magnification
-max resolution = 0.2 micrometers
-cannot see objects smaller than 0.2 micrometers ( ribosomes, lysosomes)
- anything closer than 0.2 micrometers will be seen as the same object
- max magnification= X 1500
- can see specimen in colour
-can be used to see living specimen
31
Two types of electron microscopes?
Transmission electron microscopes
Scanning electron microscopes
32
Properties of transmission electron microscopes?
TEMs
-electrons form an image
-electromagnets focuses a beam of electrons from underneath the sample
-beam of electrons form underneath specimen, electromagnets ensure focus
-denser the specimen= more electrons absorbed= denser on image
- resolution= 0.1nm max
- max magnification = X1 500 000
-photomicrograph, picture or image can be formed
-beams of electrons, not light so no colour
- complex preparation to form slides, staining, thin, need to be in a vacuum
-needs vacuum otherwise particles in air affect beam of electrons
-harder to look at live organisms, specimen needs to be dead
-cannot build an ideal image with thin specimen, too thick- blacked out image
-artefacts possible
33
Properties of scanning electron microscope?
-electrons from above passed back and forth
-electrons scatter, 3D image can be built
-resolution 20nm
-specimen doesn't need to be as thin, electrons aren't being absorbed
- vacuum
-artefacts
34
How do scientists determine artefacts?
-use many preparation techniques to check if it always shows on the image.
-prepare many slides of the same thing
-if something is missing, artefact
35
How to prepare a temporary mount?
1. Water drop on slide using pipette
2. Specimen placed onto slide with water droplet using tweezers
3. stain places on specimen using a pipette
4. cover slip slowly placed onto stained specimen using a mounted needle
36
Process of homogensiation?
-The cells are grounded in homogeniser to break open the plasma membrane and release the organelles into the homogenate
-Solution (homogenate) must be:
Ice cold- prevent enzyme activity
Buffered- prevent enzymes from denaturing
Isotonic- same water potential as cells/ organelles
-cells are then filtered to remove whole cells and debris that had not broken up
37
Process of cell fractionation?
-test tubes containing the homogenate are spun in a centrifuge on a slow speed
-heaviest organelles like the nuclei get flung to the bottom of the test tube
-form a pellet at the bottom of the test tube
-rest of the organelles stay suspended in the fluid above, the supernatent
-supernatent is drained off poured into another tube, and spun in the centrifuge at an even higher speed.
-process is repeated at higher and higher speeds until all the organelles are separated out.
38
What are the 4 stages of the cell cycle?
Mitosis
Gap phase 1
Synthesis
Gap phase 2
39
What happens during the gap phases?
Organelles and proteins making copies
Cell getting larger, growth
40
What happens during synthesis?
DNA (chromosomes) making copies
41
What is the structure of a chromosome?
A single stranded chromosome goes through interphase which results in two chromatids that are identical to each other being attached by a centromere in the centre
42
What are the stages of mitosis?
Prophase
Metaphase
Anaphase
Telophase
43
What happens during prophase?
-chromosomes condense, become visible
-centrioles (proteins) move to opposite ends of the cell (poles)
-nuclear envelope starts to break down
-chromosomes loose in cytoplasm
44
What happens during metaphase?
-chromosomes line up on equator of cell (spindle equator)
-centrioles produce spindle fibres, attach to centromeres
45
What happens during anaphase?
-spindle fibres start to contract, split centromere and chromatids are pulled to opposite poles
-sister chromatids moving to opposite poles of the spindle
46
What happens during telophase?
-nuclear envelope wraps around chromosomes, reforms
-cytoplasm begins to divide
-chromosomes unfold
47
What happens during cytokinesis?
-cell membrane splits
-formation of 2 genetically identical daughter cells
48
Process of binary fission
Single circular DNA and plasmids go though DNA replication
Parent cell divided into two cells, with the cytoplasm roughly halved between the two daughter cells
Two daughter cells each contain a single copy of the circular DNA molecules and a variable number of plasmids
49
what is the equation for serial dilutions?
C1V1 = C2V2
inital concentration X initail volume = final concentration X final volume
50
What is the fluid mosaic model?
Fluid=
Phospholipid bilayer where each phospholipid can move relative to each other. The membrane id flexible with a constantly changing shape.
Mosaic=
Proteins embedded in the bilayer which vary in shap
51
How does the cell membrane work when substances are trying to pass through?
Water soluble substances cannot move through phospholipid bilayer
Lipid soluble substances can diffuse through phospholipid bilayer.
Water is an exception, it is a very small polar molecule that can move through via osmosis
52
What are surface proteins used for?
Mechanical support
53
What is the function of the cholesterol attached to some of the phospholipids?
-hydrophobic
-helping phospholipid bilayer control what can and can't go through
- add strength and stability
- makes a little less fluid and less flexible (reduces membranes permeability)
- if cholesterol wasn't there too many substances would be able to move through.
54
What is a channel protein?
Water filled Pore/ hole in the middle, allow certain substances through
55
What is a carrier protein?
Allows large substances to bind, changes structure to allow them through
56
What is the name of a substance with a carbohydrate on top of a protein?
Glycoprotein
57
What is the name of a carbohydrate on top of a lipid?
Glycolipid
Phospholipid
58
What is the function of a glycolipid?
Receptor for chemicals
59
What is the function of a glycoproteins?
Receptors for hormones and neurotransmitters
60
What are the two factors that affect the permeability of the cell surface membrane?
Temperature
Solvents / alcohol
61
How does temperature affect the permeability of the cell surface membrane?
**Under 0°C**
- proteins denature
- holes in membrane
-not controlling what can diffuse through them
-ice crystals form
- when thawed they leave a hole
**0 - 45°C**
- low permeability
**45°C +**
- proteins denature
- holes in membranes
- phospholipids start to melt
62
How do solvents / alcohol affect the permeability of the cell surface membrane?
Dissolve phospholipids
63
What is the difference between plasma membranes and cell surface membranes?
Plasma membranes are partially permeable and refer to all membranes within the cell meanwhile cell surface membranes refer to membranes around the cell and are also partially permeable.
64
What are the functions of the cell surface membrane?
- controls what enter and leaves cells
- allow different conditions inside and out of cells.
65
What is the definition of diffusion?
The passive net movement of particles down a concentration gradient until equilibrium is reached.
66
What is simple diffusion?
Lipid soluble, small, non polar molecules are able to diffuse through the phospholipid bilayer.
67
What are factors that affect simple diffusion and how?
**surface area**
- larger surface area= faster diffusion
**concentration gradient, difference between the high and low concentration**
- larger concentration gradient = faster diffusion
**diffusion pathway, pathway diffusion takes**
- small diffusion pathway = diffusion happens faster
**temperature**
Increases= more kinetic energy
68
What is facilitated diffusion and how does it work?
Substances diffusion through either channel proteins or carrier proteins.
Large molecules move through carrier proteins.
Large substances bind to carrier proteins.
Carrier protein change shape, substance usable to diffuse to other side of membrane.
Anything that is charged move through channel proteins.
Ions, polar molecules.
69
What are factors that affect facilitated diffusion?
**number of proteins**
Not enough proteins for substances to bind to = slower rate of diffusion
**concentration gradient**
70
Definition of osmosis?
The movement of water particles over a partially permeable membrane from a high water potential to a low water potential;
71
What is water potential?
- the pressure of water particles in a solution
- kPa
- pure water= 0 kPa
- more negative number= lower water potential
72
How does a cell behave in a hypertonic solution?
- water move out of the cell as the water outside
- has a lower water potential than inside so water moves out to the lower concentration from high
73
How do cells behave in a hypotonic solution?
- water moves into the cell by osmosis as the water potential inside the cell is lower than the water potential outside.
74
What is a hypotonic solution?
When the water potential of a solution is more positive than the cell
75
What is a hypertonic solution?
When the water potential of a solution is more negative than the cell
76
How do cells behave in an isotonic solution?
Water does not move by osmosis as the water potential is the same both outside and inside the cell by osmosis
77
What is active transport and its process?
The movement of particles from an area of low concentration to an area of high concentration across a cell membrane, using ATP and carrier proteins
For active transport to occur, the particle must bind to a specific site in the carrier protein.
On the inside of the cell, ATP also binds to the carrier proteins
The ATP is then hydrolysed to ADP and Pi which causes the carrier protein to change shape.
The carrier protein is now open to the other side of the membrane and the particle is released.
The phosphate molecule is then released from the carrier protein, which causes the carrier protein to return to its original shape.
78
What is co transport and its process?
Cotransport uses ions to move substances into and out of cells. This occurs partially in epithelial cells of the ileum. Sodium and potassium ions are pumped out of the epithelial cells by active transport into blood leaving a lower concentration in the cell, causes these ions to move into the lumen by facilitated diffusion, which at the same time brings glucose and amino acids into the cell. These then diffuse from a high concentration in the epithelial cells by to a low concentration in the blood.
79
What factors affect active transport?
- respiration
- density of carrier proteins
80
what is phagocytosis in simple terms?
when a white blood cell engulfs a pathogen
81
what are non-self cells?
cells that our body recognise as foreign due to their foreign antigen
examples:
pathogen
transplants/ transfusions
cancer cells
toxins
82
what are self cells?
cells that are ours, and from our bodies
83
what are antigens?
a protein on the cell surface of our cells, a foreign antigen is one that is of non-self cells
84
What is the process od the non specific immune response of phagocytosis?
-the phagocyte detects the pathogen due to foreign antigens
-phagocyte is attracted to pathogen due to chemicals that the pathogen is producing
-cell membrane of the phagocyte pinches around the pathogen forming the vesicle around the pathogen
-the lysosomes in the phagocyte release lyzozymes and fuse with the membrane of the phagosome to breakdown the pathogen
-phagocyte presents pathogens antigens on its surface
-the digested products are then either absorbed by the cytoplasm or leave the cell by exocytosis
85
what are the specific immune responses?
humaral response (happens in the blood)
cell mediated response (t cells/lymphocytes)
86
where do the T cells mature
thymus gland
87
what are the non specific immune responses
physical barriers
phagocytosis
88
what is an antigen presenting cell
when the body cells infecting with a virus takes the antigen from the pathogen and puts it on its own surface
89
What is the cell mediated immune response?
-stimulates more phagocytosis, ensures other pathogens in the body are englufed and digestees
-memory T cell means faster response if infected again
-stimulates b cells
-**cytoxin T cell releases perforin which causes holes in the body cell, it ensures anything can move in or out so the body cell ends up dying
90
what is the process of the humoral response?
-pathogen binds to the complementary receptor antigen of the B cell (produced and matured in the bone marrow)
-endocytosis causes the B cell to only engulf the antigen on the pathogen
-the B cell becomes antigen presenting and binds to a T cell
-clonal selection and mitosis causes multiple clones of the B cell to be created
-these differentiate into either plasma cells that make antibidoies or memory cells that stay in the body forever
91
what is the structure of an antibody
-quaternary structure due to 2 light chains and 2 heavy chains
-disulfide bridges hold the chains together
-contains a constant region which is the same for each antibody and a variable region that varies depending on the pathogens antigen
92
what is agglutination
where antibodies clump microbes together due to them being able to make up to 2 antigen-antibody complexes
93
what is antigen variability
where the antigen of a pathogen chnages shape and therefore cannot be fought by an antibody as they are no longer complementary
94
what are uses of monoclonal antibodies
-diagnosis of infections
-treatment
-pregnancy testing
-detecting certain cancers
95
how do monoclonal antibodies help in the diagnosis of infection
-bind protein with fluorescent lable to variable region of antibody
-only becomes fluorescent when antigen-antibody complex is made
-radioactive chemicals attached to antibody
-can detect various diseases
96
how do monoclonal antibodies help in treatment
-attach chemotherapy drug to monoclonal antibodies, inject
-immunotherapy- kill only cancer cells specifically
97
how do monoclonal antibodies help in pregnancy
-antibody binds to HCG (hormone released if pregnant) body cells
-colour change from colourless to pink indicated pregnancy
98
what is the process of a direct ELISA
-target proteins attached at the bottom of beaker, unaware of the concentration
-antibodies specific to the target proteins are added to the beaker
-wash out any unbound antibodies
-cplour change is measured by a colorimeter
99
what are vaccines
a way of introducing dead/ weakened pathogens into the body to stimulate the production of antibodies and memroy cells
100
what are ethical issues with vaccinations
-tested on animals first
-humans in clinical tests may themselves at risk because they believe they may be 'immune'
-some people refuse over fear of side effects, they are protectedby herd immunity in the same way people who can't get the vaccime
-new disease= difficult decisions to who recieves it first
101
why can't vaccinations eliminate all diseases?
-fails to induce immunity in some people (immunodeficiency)
-people get infected before enough antibodies are generated by vaccine to afford protection
-antigenic variability- pathogen mutates and vaccines no longer work
-many different strains cant be fought at oncce
-objections to vaccinations based on moral, ethical or religious reasons
102
what is natural immunity?
breast feeding children from birth can cause them to retain some immunity in breast milk
103
what is active immunity?
the body makes antibodies after being exposed to a foreign antigen stimulating an immune response
104
what are examples of active immunity
vaccination
having had the disease before
105
what is natural active immunity
become immune after catching disease
106
what is artificial immunity?
become immune after being given a vaccination
107
what is passive immunity
when the body is given antibodies through placenta/ breast milk
108
what is artificial passive immunity
when injected with antibodies
109
what are the stages for the onset of aids
-transmission
-acute infection, last 3/4 weeks and flu like symptoms
-latency period, can last years, HIV is dormant and antiretrovirals keep into this phase for a long time
-AIDS develop
110
what is the structure of HIV
-attachment proteins, glycoproteins
-capsid
-reverse transcriptase enzymes
-viral DNA
-viral phospholipid envelope
111
what happens during HIV replication?
- attachment proteins attach to the CD4 receptors on the cell membrane of the host helper T-cell
-the capsid is released into the T-helper cell where it releases its genetic materisal
-reverse transcriptase reverse transcribes the viral RNA into viral cDNA
-the viral cDNA inserts itself into the human DNA
-the host cell machinary transcribes and translates this
-viral proteins are made
-viral proteins leave the vcell, each taking a part of the cell membrane
-T helper cell dies
112
what is a monoclonal antibody?
antibodies with the same tertiary structure that are produced from cloned plasma B cells
