TOPIC B1- CELL BIOLOGY Flashcards
organisms can be what
-prokaryotes
-eukaryotes
explain what eukaryotic cells are
-animal and plant cells
-have a cell membrane
-cytoplasm
-genetic material enclosed in nucleus
explain what prokaryotic cells are
-smaller and simpler e.g bacteria
consist of
-cytoplasm
-cell membrane
-cell wall
-genetic material not in a nucleus
-single DNA loop
what is a nucleus
contains genetic material that controls the activities of the cell
what is a cytoplasm
a gel-like substance where most chemical reactions happen
-it contains enzymes that control the reactions
what is a cell membrane
holds the cell together and controls what goes in and out
what is a mitochondira
where most reactions for aerobic respiration take place
what is a ribosome
where proteins are made
Most animal cells have
-a nucleus
-cytoplasm
-cell membrane
-mitochondria
ribosomes
plant cells have
ALL SAME AS ANIMAL
-a nucleus
-cytoplasm
-cell membrane
-mitochondria
-ribosomes
AND
-chloroplasts
-permanent vacuole filled with cell sap
state what is found in an animal cell
-nucleus
-cytoplasm
-cell membrane
-mitochondira
-ribosome
what is a rigid cell wall
-made of cellulose
-supports the cell and strengthens it
what is a permanent vacuole
contains a cell sap, a weak solution of sugar and salts
what is chloroplasts
where photosynthesis occurs, they contain a green substance called chlorophyll, which absorbs light
what is different about plant cells to animal cells
they also contain
-a rigid cell wall
-permanent vacuoles
-chloroplasts
bacteria are …
prokaryotes
state what is found in a bacterial cell
-cell membrane
-cytoplasm
-cell wall
-a singular strand of DNA that floats freely in the cytoplasm
-plasmids
state what light electrons use
-light and lenses to form an image of a specimen and magnify it
-let us see individual cells and large subcellular structures, like nuclei
state what electron microscopes use
-electrons instead of light to form an image
-have a higher magnification
-higher resolution to light microscopes
explain why electron microscopes are better than light ones
-they let us see much smaller things in more detail e.g mitochonria
-higher resolution
-higher magnification
formula for magnification
magnification= image size
real size
resolution definiton
the ability to distinguish between 2 points
differentiation meaning + when does it happen most
the process where a cell changes to become specialised for its job
-as organisms develop
state 5 specialised cells
-sperm cells
-nerve cells
-muscle cells
-root hair cells
-phloem and xylem cells
state what sperm cells do
-specialised for reproduction
-**function **is to get male DNA to female DNA.
-has a long tail and streamlined head to help it swim to the egg
-lots of mitochondria in the cell to provide energy
Features of sperm cells which aid function
Midpiece is packed with- mitochondria to release energy for the tail
Tail rotates- propelling the sperm cell forward and allowing it to move
nerve cells
specialised for** rapid signalling**
-carries electrical signals from one part of the body to the other
How are they adapted
-cells are long and have branched connections at their ends to connect other nerve cells and form networks
-axons covered with a fatty sheath, speeding up nerve impulses
muscle cells
specialised for contraction
how are they adapted
-contain lots of mitochondria to generate energy
root hair cells
specialised for absorbing water and minerals
how are the root hair cells adapted
-long hairs that stick out into the soil
-big surface area for absorbing water and mineral ions from the soil
-mitochondria releases energy for active transport
xylem
-to transport water and dissolved ions
Special features aiding function
-no walls between cells to form continuous hollow tubes through waters drawn upwards
-cells contain no organelles or cytoplasm, allowing for free passage of water
-outer walls are thickened with substances called lignin
Phloem
transport of dissolved sugars and amino acids
FEATURES
-cells are joined end to end and contain holes in the end cell walls
-few subcellular structures
what are chromosomes?
-they contain genetic infomation
-coiled up lengths of DNA molecules
-in body cells the chromosomes are found in pairs
why does the cell cycle make new cells
for
-growth
-development
-repair
what is mitosis
the stage of a cell cycle when the cell divides
-multicellular organisms use mitosis to grow or replace cells that have been damaged
what are the 2 main stages of the cell cycle
-growth & DNA replication
-mitosis
Mitosis
-During the cell cycle the genetic material is** doubled** and then divided into two identical cells.
-Before a cell can divide it needs to grow and increase the number of sub-cellular structures such as ribosomes and mitochondria. The DNA replicates to form two copies of each chromosome.
-In mitosis one set of chromosomes is** pulled** to each end of the cell and the nucleus divides.
-Finally the cytoplasm and cell membranes divide to form** two identical cells.**
explain dna replication
-before dividing the cell has to grow and increase the amount of subcellular structures e.g mitochondria and ribosomes
what are undifferentiated cells called and their significance
-stem cell of an organism which is capable of giving rise to many more cells of the same type, and from which certain other cells can arise from differentiation.
-found in human embryos
Embryonic stem cells
-on the inside layer of an embryo
Potential- Undifferentiated
Produced- all different types of specialised cells found in body
Adult stem cells sources
-bone marrow
pot- limited availability to differentiate and mainly cells of blood are produced
Stem cells, skin
-limited availability to differentiate
-cells found in different layers of skin are produced
stem cells, liver and brain
-limited availability to differentiate
-cells found in organs are produced
stem cells meristem
-tips of roots and shoorts
-fully undifferentiated
-one cellhas ability to divide
Treatment with stem cells
Diabetes
Issue- inability for pancreas to produce insulin to control blood sugar levels
Stem cells treatment- they could be differentiated into insulin and produce pancreatic cells
Source- stem cell donors or therapeutic clothing
Paralysis
Issue- damage to nerve cells in brain and spincal cord, preventing signals from brain to reach muscles in part of the body
Stem cells treatment- they could be differentiated into nerve cells, which are transplanted into damaged regions of the nervous system
Source- stem cell donors
state why some people are against stem cell research
-they feel human embryos shouldn’t be used for experiments, as each is a potential human life
-some embryos used are unwanted ones from fertility clinics
Therapuetic cloning
an embryo is produced with the same genes as the patient.
-Stem cells from the embryo are not rejected by the patient’s body so they may be used for medical treatment.
Risks of stem cells in medicine
-they can be cultured in the lab and become infected with a virus, which could be transmitted to the patient
-risk of cultured stem cells accumulating, leading to cancer cells
-low number of stem cell donors
Social and ethical issues of using stem cells in medicine
-a lack of peer reviwed clincal evidence of the success of stem cell treatments
-educating public sufficiently about what there used for
define diffusion
the spreading out of particles from an area of higher concentration to an area of lower concentration
state 3 ways that makes diffusion happen quicker
-bigger concentration gradient, the greater the difference in concentration between 2 regions the faster the overall rate of diffusion
-higher temperatures, more kinetic energy the particles of the substance will have
-greater the surface area,
state what molecules can diffuse through cell membranes
-oxygen and carbon dioxide in gas exchange
-glucose
-amino acids
-water
Why do single-celled organims have relatively large surface area to volume ratio
to allow sufficient transport of molecules into and out the cell to meet needs of the organism
LEARN CALCULATING SURFACE ARE TO VOLU RATIOS
State the adaptations for exchange in animals
Small intestine
-villus has good blood supply, maintaing a concentration gradient
-1layer of epithelial cells cover the surface of each villus, decreasing diffusion
State the adaptations for exchange in animals
the lungs
-millions of alveoli, to provide a huge SURFACE AREA
-wall of alveolus is 1cell thick, to maintain concentration gradient
State the adaptations for exchange in animals
the gills fish
-each gills made from lots of smaller plates called filaments, to increase SA
-dense capillary network ensures good blood supplu, to maintain concentration gradient
define osmosis
the movement of water molecules across a partially permeable membrane from a region of higher water concentration to a region of lower water concentration
osomosis is a
type of diffusion
what type of molecules move by osmosis
water
active transport
-movement of particles against a concentration gradient, from an area of lower concentration to an area of higher concentration using energy transferred during respiration
root hairs
-each branch of a root will be covered in millions of microscopic hairs
-gives the plant a large surface area for absorbing water and mineral ions from soil
-plants need these for healthy growth
Active transport in plants
-root hair cells line the surface of plant roots to move minerals like magnesium ions
-magnesium ions needed to make chlorophyll
-nitrate ions needed to make amino acids
active transport needs energy from what
respiration
cells use diffusion to take in substances they need and get rid of waste products
-oxygen + carbon dioxide are transferred between cells and the environment during gas exchange
-in humans urea diffuses from cells into the blood plasma
how are exchange surfaces adapted to maximise effectiveness
-thin membrane, so substances have short distances to diffuse
-large surface area so lots of substances can diffuse at once
-exchange surfaces in animals have lots of blood vessels
where does gas exchange happen
in the lungs
-the job of lungs is to transfer oxygen to the blood and to remove waste carbon dioxide from it
-lungs contain millions of air sacs called alveoli where gas exchange happens
how are alveoili adpated
-enormous surface area
-moist lining for dissolving gases
-thin walls
-good blood supply
to maximise the diffusiom of O2 AND CO2
importance of the villi
-inside a small intestine
-increase surface area in a big way so digested food is absorbed quicker into blood
-they have a single layer of surface cells
-good blood supply to assist quick absorption
explain how the structure of leaves let gases diffuse in and out of cells
-underneath of leaf is an exchange surface, and is covered in stomata
-oxygen and water vapour also diffuse out through the stomata
-walls of cells inside the leaf form more exchange surfaces
-air spaces increase the area
how do gills have a large surface area for gas exchnage
-gill filaments, that give a big surface area for exchange of gases
-covered in lamellae, increasing the surface area
-thin surface layer of cells to minimise distance that gases need to diffuse
