cells Flashcards
What are the functions of lysosomes?
- hydrolyse phagocytic cells
- exocytosis - releases enzymes to the outside of the cell to destroy material
- completely break down dead cells (autolysis)
What are the functions of Golgi Apparatus?
- secrete carbohydrates
- form lysosomes
- transport, modify and store lipids
- add carbohydrates to form glycoproteins
- produce secretory enzymes
- molecules are ‘labelled’ with their destination
What are the functions of mitochondria?
- site of ATP production
- site of aerobic respiration
- has the DNA that codes for the enzymes needed for respiration
What are the functions of a nucleus?
- site of DNA replication and transcription (making mRNA)
- contains the genetic code for each cell
What are the functions of the SER?
- synthesis
- stores lipids and carbohydrates
What are the two types of electron microscopes?
- scanning electron microscope (SEM)
- transmitting electron microscope (TEM)
What is the formula for magnification?
magnification = size of image / size of object
What are the features of an SEM?
- SEMs knock electrons off the specimen and these electrons come together to form an image
- SEM images can be three-dimensional
- Specimens do NOT have to be thin like when using a TEM
- Resolution is lower than that produced by a TEM
What are the features of a TEM?
- TEMs use electromagnets to focus the electron beam
- TEMs are high resolution microscopes
- in thin specimens, you can see the internal structures of organelles such as chloroplasts
What is meant by ‘membrane-bound organelle’?
an organelle that is surrounded by a phospholipid layer
Examples of membrane bound organelles
- mitochondria
- endoplasmic reticulum (SER and RER)
- chloroplasts
- lysosomes
- nucleoli & nuclei
Examples of non-membrane bound organelles
- ribosomes
- cytoskeleton
- centrioles
What is meant by magnification?
how many times bigger the image is compared to the object
What is meant by resolution?
the minimum distance that objects can be in order for them to appear as separate things
Why is a solution cold in homogenisation?
so the the rate of enzyme (lysosyme) activity is decreased
Why is a solution buffered in homogenisation?
it maintains a constant pH so it does not denature proteins
Why is a solution isotonic in homogenisation?
has the same water potential as the tissue so no net movement of water by osmosis, so this prevents cell lysis
What are ribosomes made of?
- ribosomal RNA and proteins
What is the maximum resolution of an optical microscope?
0.2um
What is the maximum magnification of an optical microscope?
x1,500
What is the maximum magnification of a TEM?
x500,000
What is the maximum resolution of a TEM?
0.0001um
Limitations of EMs (in general)
- can’t view live specimens/process due to the interior of the microscope being in a vacuum
- specimen has to be sliced very thinly
- requires an extensive staining process that can lead to artefacts
What is the maximum resolution of an SEM?
0.0001um
What is the maximum magnification of an SEM?
x100,000
What are the 3 stages of interphase?
- G1
- S
- G2
What happens in the G1 phase?
the cell grows and makes a new set of organelles and proteins for the daughter cells
What happens in the S
phase?
- the DNA in the cell is replicated, so that the two daughter cells can each get one set of DNA
- also a checking of genetic material in this phase
- summary: synthesis of new DNA
What happens in the G2 phase?
- cell growth continues
- synthesis of special proteins in preparation for mitosis
What is mitosis necessary for?
- growth
- replacing/repairing cells
- asexual reproduction
What are the stages of mitosis?
- Prophase
- Metaphase
- Anaphase
- Telophase
What happens during prophase?
- chromosomes condense and are now visible when stained
- nuclear envelope breaks down
- nucleolus disappears
What happens during metaphase?
- chromosomes line up at the equator of the cell
- spindle fibres reach the chromosomes and attach to the centromeres
- each sister chromatid is attached to a spindle fibre
What happens during anaphase?
- the sister chromatids separate at the centromere
- spindle fibres begin to shorten
- the separated sister chromatids (now called chromosomes) are pulled to opposite poles by the spindle fibres
What do prokaryotes have instead of mitochondria?
mesosomes - attach to cell membrane
What are the functions of glycoproteins?
- acts as recognition sites
- help cells attach to one another + form tissues
why are phospholipids present in cell membranes
they form a stable barrier that regulates what enters and exits the cell
why are proteins present in cell membranes
- cell-cell recognition
- selective transport
- structural support
why are glycoproteins present in cell membranes a level biology
- cell-cell recognition (helps recognise antigens from pathogens)
- cell adhesion (helps form tissues and provide structural integrity)
- cell signalling (act as receptors that receive signals from hormones and neurotransmitters, and relay these signals to the inside of the cell)
what is facilitated diffusion
net movement of large polar molecules or ions moving from area of high conc. to area low conc. using carrier proteins and protein channels
what is simple diffusion
Simple Diffusion is the net movement of particles down a concentration gradient, from a high concentration to low concentration.
the two types of diffusion are?
- simple
- facilitated
what is osmosis
the passage of water from a region where it has a higher water potential to a region where it has lower water potential down the water potential gradient through a selectively permeable membrane
what does cholesterol do for the cell surface membrane?
- restricts lateral movement of other molecules
- makes membrane less fluid at high temperatures
- prevents leakage of water and dissolved ions from the cell
what are the type of molecules that can’t pass through the membrane
- water soluble
- large molecules
what is meant by water potential
the pressure caused by water molecules
Which cell is involved in the humoral immunity?
B-lymphocyte
What is an antigen
a protein that is part of the cell-surface membrane of invading microbes or diseased cells
Which cell is involved in the cell-mediated response?
T-lymphocyte
Where do B-lymphocytes mature in?
Bone marrow
Where do T-lymphocytes mature in?
Thymus gland
What are T-lymphocytes activated by?
antigen presenting cells
What are examples of antigen presenting cells?
- body cells (host cells) invaded by a virus
- transplanted cells
- cancer cells
- phagocytes
What cells release antibodies?
plasma cells
what is a monoclonal antibody?
an artificially produced antibody that binds and neutralises one specific antigen
what are the uses of monoclonal antibodies
- medical testing
- medical diagnosis
- pregnancy tests
what is a benefit of using monoclonal antibodies when treating cancer?
reduces harmful side effects of chemotherapy/radiotherapy
what type of diseases can monoclonal antibodies be used to diagnose?
- prostate cancer
- hepatitis
- covid-19
- chlamydia
how many antibodies does the ELISA test use?
2
what activates b-lymphocytes
t-lymphocytes
what to b-lymphocytes divide into?
plasma cells
list the steps involved in the immune response
- phagocytosis
- activation of t-lymphocytes
- activation of b-lymphocytes
- production of antibodies
what activates t cytotoxic cells
t helper cells
