Cell Structure Flashcards
what do cells do in order to become specialised
differentiation
how are types of cells different to each other
they all contain the same genetic information but depending on what role a cell needs to play
what happens to a cell when it differentiates
it develops a structure and composes subcellular structures which enables it it carry out a certain function
what are adult stem cells and what are they mainly involved in
undifferentiated cells that retain their ability to specialise throughout adulthood
involved in replacing and repairing cells
what is a specialised cell
those which have developed certain characteristics in order to perform particular functions. these differences are controlled by the nucleus
what does a ciliated cell do and what are its adaptations
- movement of mucus in the trachea and bronchi
has extensions of the cytoplasm at the surface of the cell to form hair-like structures called cilia
what does a nerve cell do and what are its adaptations
- conduction of impulses
- long so it can stretch to different parts of the body
- cell has extensions and branches so that it can communicate with other nerve cells and muscles and glands
- the axon is covered with a fatty sheath which insukates the nerve cell and speeds up the nerve impulse
what does a nerve cell do and what are its adaptations
conduction of impulses
- long so that they can stretch to and from different parts of the body
- cell has extensions and branches so that it can communicate with other nerve cells, muscles and glands
- the axon has a fatty sheath to insulate it and speed up the nerve impulse
what does a red blood cell do and what are its adaptations
transport of oxygen
- biconcave disk
- contains haemoglobin
- contains no nucleus
what does a sperm cell do and what are its adaptations
reproduction
- haploid nucleus
- tail
- packed with mitochondria
- contains digestive enzymes in the acrosome to penetrate the egg
what does a egg cell do and what are its adaptations
reproduction
- contains a lot of cytoplasm which contains a lot of nutrients
- haploid nucleus
- cell membrane has the ability to shut out more sperm after one has got through
what are some examples of specialised cells in animals
ciliated
nerve
egg
sperm
red blood
what are some examples of specialised cells in plants
root hair cell
xylem vessel
palisade mesophll cell
what does a root hair cell do and what are its adaptations
absorption of water an minerals from soil
- root hair increases surface area
- walls are thin
- no chloroplasts present
what does a palisade mesophyll cell do and what are its adaptations
photosynthesises
- column shaped so they can be closely packed together and maximise absorption of sunlight
- contains many chloroplasts for maximum photosynthesis
what does a xylem vessel do and what are its adaptations
conducts water through plant and supports it
- no top or bottom walls so that between vessels there is a continuous column
- cells are dead to allow free passage of water
- lignin cell walls to keep support
what is a stem cell
an undifferentiated cell that is capable of diving to produce more stem cells or other cell types through differentiation
what are the three types of stem cell
embryonic
adult
meristem
where are embryonic stem cells found
on the inside layer of an embryo
where are adult stem cells found
bone marrow
skin
umbilical cord blood
other organs such as liver and brain
what is similar about embryonic and meristem cells
they are both undifferentiated and unspecialised
why are adult stem cells not entirely useful
they have a limited ability to differentiate
what cells can be produced from an embryonic stem cell
all the types of specialised cell found in the body
what cells can be produced from an adult stem cell found in the skin
skin cells and hair follicles
what cells can be produced from meristem cells
one cell has the ability to produce a whole new plant
where are meristem cells found
in the tips of roots and shoots (the growing regions of plants)
what cells can be produced from an adult stem cell found in the bone marrow
mainly blood cells (red blood cells, cells of the immune system)
what cells can be produced from an adult stem cell found in the umbilical cord blood
cells of the blood (red and white), muscle and nerve tissue
what cells can be produced from an adult stem cell found in other organs such as the liver and brain
cells found in these organs
what does the term totipotent mean
they can form all of the different tissues and organ needed during development
embryonic stem cells are totipotent
what is the main role of adult stem cells
to replace cells lost through damage or to produce new cells for growth
what is type 1 diabetes
inability of the pancreas to produce insulin to control blood sugar levels
how can stem cells treat type 1 diabetes
stem cells could be differentiated into insulin - producing pancreatic cells which are transplanted into the patients body
where would you source the stem cells for treating type 1 diabetes
stem cell donors or therapeutic cloning
where would you source the stem cells needed for treating paralysis
stem cell donors or therapeutic cloning
what is paralysis
damage to cells in the spinal cord, preventing signals from the brain reaching muscles in parts of the body resulting in loss of movement
how could stem cells treat paralysis
stem cells could be differentiated into nerve cells which are transplanted into the damaged region of the nervous system
what is therapeutic cloning
where:
- an embryo is produced with the same genes as the patient
- a 5-day embryo is the best source for embryonic stem cells
- stem cells from embryos created in this way are not rejected by the patients body which means they don’t have to take drugs to suppress their immune system
what is therapeutic cloning
where:
- an embryo is produced with the same genes as the patient
- a 5-day embryo is the best source for embryonic stem cells
- stem cells from embryos created in this way are not rejected by the patients body which means they don’t have to take drugs to suppress their immune system
what are the benefits of using stem cells in medicine
- great potential to treat a variety of medical problems
- organs developed from their own stem cells are less likely to be rejected + no waiting for organ donation
- adult stem cells are already successfully used in treatments
what are the general risks and issues of using stem cells in medicine
- stem cells cultured in a lab could become injected and pass this on to patient
- risk of cultured stem cells growing out of control and developing into cancer cells
- low numbers of stem cell donors
what are the ethical and social issues of using stem cells in medicine
if using embryonic stem cells:
- harm/death to embryo
- embryo can’t give consent
- should embryos even be treated with human rights
educating the public sufficiently about what stem cells can and cant be used for
embryonic cells may be sourced from unused IVF treatment - who gives permission
what is an enzyme
a biological catalyst for metabolic reactions
what stores does photosynthesis transfer energy from and to
from light energy to chemical energy
what is the structure of the human alimentary canal
mouth, oesophagus, stomach, small intestine (duodenum and ileum), large intestine (colon and rectum) and pancreas
what is transpiration
the evaporation of water from the surface of a plant
what does urine contain
water, urea and ions
what is homeostasis
the maintenance of a constant internal environment
what are some examples of homeostasis
body water content
body temperature
what is a mutation
a rare, random change in genetic material that can be inherited
how can scientist ensure that vaccines contain harmless pathogens
- kill the pathogen
- make the pathogen unable to grow or divide
- use only fragments of pathogens
what is one example of fungi
mucor or yeast
what is a pathogenic example of a protoctist
- plasmodium causing malaria
what are two examples of protoctist and what features do they have
- amoeba that have features like and animal cell
- chlorella which are more like plants
what are examples of viruses in humans
- influenza causing flu
- HIV virus causing AIDS
what are the different ways a vaccine can be administered
- orally, nasally or via injection
how do vaccines work
- once in the bloodstream the antigens trigger an immune response:
- the lymphocytes spot the antigens and produce specific antibodies
why do vaccinations cause long term immunity
- memory cells and antibodies remain circulating in the blood stream
- therefore when the antigen is encountered again the antibodies can be produced much faster and on a much larger scale
- due to the rapid nature of the response, the pathogen is unable to cause disease
what is the importance of vaccination
- they reduce the likelihood that an infected individual will spread the pathogen to others (HERD IMMUNITY)
- they reduce the cases of certain diseases and even eradicated diseases such as smallpox
- epidemics cane be prevented
what are the disadvantages of vaccinations
- pathogens can MUTATE so the antibodies no longer recognise the pathogen rendering the vaccination useless
- side-effects can reduce the uptake in the population
what do memory cells enable
- future antibody production to occur sooner, faster and in greater quantity
what IS a platelet
a fragment of a cell involved in blood clotting
how do platelets stop the bleeding when a person is cut
- when exposed to air a series of reactions occur
- the platelets release chemicals that cause the soluble fibrinogen to convert to insoluble fibrin
- to form an insoluble mesh across the wound,
- trapping the red blood cells
- and therefore causing a clot
- this clot eventually dries and develops into a scab
what does a scab do
- it stops the flow of blood outside the body
- prevents bacteria/microorganisms entering the wound
what is the importance of blood clotting
- prevents significant blood loss
- prevents the entry of microorganisms which could cause infection
- remains in place until new skin has grown underneath it, effectively providing a seal
what functions do the kidneys provide
- regulate the water content of the blood
- excrete toxic waste products of metabolism
(osmoregulation and excretion)
what are some substances that the kidney removes from the blood
- urea
- ammonia
- excess hormones
- excess salt/ions
- creatinine
- excess water
- uric acid
describe the structure of the urinary system
- two kidneys
- ureters
- bladder
- urethra
- to outside of body
+ renal artery and vein
where are nephrons located in the kidney
- they start in the cortex and loop down into the medulla
how does the urine get from the blood to the bladder
after it is forced out of the blood:
- the contents of the nephrons drain into the renal pelvis and the urine collects there
- before it flows into the ureter
- to be carried to the bladder for storage
what is the structure of a nephron
- bowman’s capsule
- proximal convoluted tubule
- loop of Henlé
- distal convoluted tubule
- collecting duct
surrounding this is a network of capillaries with a knotted section within the Bowman’s capsule
what are the processes of the filtering of blood in the kidney
- Ultrafiltration
- selective reabsorption of glucose
- reabsorption of water and salts
what substances are filtered out during ultrafiltration and what is this called
- glucose
- urea
- water
- used hormones
- salts
glomerular filtrate
where is water reabsorbed
loop of henle and collecting duct
where are salts reabsorbed
loop of henle
where is glucose reabsorbed
proximal convoluted tubule
composition of urine
- water
- urea
- ions
how is the nephron adapted for the reabsorption of glucose
they contain many mitochondria for active transport
why can glucose only be reabsorbed in one place in the nephron
because the gates that facilitate active transport are only found in the proximal convoluted tubule
why do doctors check your urine to see if you have diabetes
because those with diabetes cannot ocntrol their blood sugar level so they are often very high
this mean not all of the glucose can be reabsorbed using active transport so much of it continues in the filtrate and ends up as urine
what is another word for bursting of cells
lysis
what is an isotonic solution
when the water potential is equal between the blood cell and the solution
describe the structure of a DNA molecule
two strands coiled to form a double helix, the strands being linked by a series of unpaired bases: adenine-thymine (AT) and guanine-cytosine (GC)
how is the structure of an RNA molecule different to DNA
the thymine is replaced by uracil
it is single stranded instead of double
what are some examples of RNA molecules
messenger RNA
transfer RNA
ribosomal RNA
what is a gene
a stand of DNA that codes for a protein
what are the processes of protein synthesis
- transcription -> DNA is transcribed and an mRNA molecule is produced
- translation -> mRNA is translated and an amino acid sequence is produced
why is mRNA needed
because DNA must remain in the nucleus so a copy (mRNA) is made to move it to the ribosomes in the cytoplasm
what are the steps of transcription
- the two strands of DNA are unzipped (using the enzyme helicase) by breaking the weak hydrogen bonds between the base pairs
- free RNA molecules are attracted to the exposed DNA by complimentary base pairing
- RNA polymerase catalyses the formation of covalent bonds between these bases to form mRNA
- the mRNA then leaves the nucleus
what are the steps of translation
- the mRNA attaches to a ribosome
- the tRNA moleculesbind to their specific amino acids
- the anticodons on each tRNA pair with the codons on the mRNA molecule
- two tRNA molecules attach at one time and a peptide bond is formed between the two amino acids
- this process continues until a stop codon on the mRNA is reached
- the amino acid chain folds into the correct shape to form a protein
what is the structure of a tRNA
- a triplet of unpaired bases at one end (anticodon)
- a region where the specific amino acid can attach at the other
