cell biology Flashcards
eukaryotic
animal and plant cells
prokaryotic
bacterial cells ( smaller than eukaryotic)
eukaryotes
made up of eukaryotic cells
prokaryotes
made up of prokaryotic cells
animal cells sub-cellular structures/organelles
nucleus, cytoplasm, cell membrane, mitochondria and ribosomes.
plant cells sub-cellular structures/organelles
same as animal but also have cell wall, permanent vacuole and chloroplast.
nucleus function
- contains DNA/genetic material that controls the activities of the cell
- enclosed in nuclear membrane
cell membrane function
- holds cell together
- controls what enters and leaves cell
cytoplasm function
- gel-like substance
- where most chemical reactions occur
- contain enzymes (control rate of reaction)
- where organelles are found
ribosomes function
- where protein synthesis occurs
- found on structure called the rough endoplasmic reticulum
mitochondria function
- where most reactions for aerobic respiration take place
- provide energy for cell
cell wall (also in algal cells) function
- made of cellulose
- supports cell and strengthens
permanent vacuole function
- contain cell sap
- found in cytoplasm
- improve cells rigidity
- weak solution of sugar and salts
chloroplast function
- where photosynthesis takes place, providing food for plant
- contain chlorophyll (green pigment) which absorbs light needed for photosynthesis
bacterial cells sub-cellular structures/organelles
cytoplasm, cell membrane, cell wall, plasmids, single circular strand of DNA
cell wall (bacterial) function
- made of peptidoglycan
singular strand of DNA function
- floats freely in cytoplasm (no nucleus)
plasmids function
- small rings of DNA (may be one or more)
order of magnitude
used to understand how much bigger or smaller a cell is to another
milli to metres
x 0.001
centi to metres
0.01
micro to metres
x 0.000,001
nano to metres
x 0.000,000,001
light microscope
- first cells of a cork observed by Robert Hooke in 1665
- has an objective lens and eyepiece lens
- illuminated from underneath
- form an image of specimen and magnify it
max magnification of 2000 and resolving 200nm - view tissues, cells and large sub-cellular structures
electron microscope
- developed in 1930s
- can view deep inside sub-cellular structures eg mitochondria, plasmids and ribosomes
- form an image using electrons (have smaller wavelength than light waves)
- scanning electron microscope: creates 3D image
- transmission electron microscope: creates 2D images detailing organelles
- An electron microscope has much higher magnification and resolving
power than a light microscope. - This has enabled biologists to see and understand many more sub-cellular structures.
resolution
ability to distinguish between two points, higher resolution = sharper image
magnification
how much bigger an image appears compared to the original object
magnification calculation
image size/real size
sperm cells
-specialised to carry male’s DNA to the egg cell for successful reproduction
- streamlined and long tail to aid swimming
- many mitochondria = supply energy
- acrosome (head) carries digestive enzyme, break down outer layers of membrane of egg cell
differentiation
-process which cells change to become specialised suited for its role
- could develop different sub-cellular structures
nerve cell
- specialised to transmit electrical signals quickly from one place in the body to another
- axons long to cover more distance
- (dendrites) branched connections at their ends to connect nerve cells and form a network around the body
- nerve endings have a lot of mitochondria, supply energy to make special transmitter chemicals called neurotransmitters, allow impulse to be passed
muscle cells
- specialised to contract quickly to move bones or squeeze, cause movement
- special proteins slide over each other to contract
- lots of mitochondria t provide energy from respiration for contraction
- can store glycogen
- long
root hair cells
- specialised to absorb water by osmosis and mineral ions by active transport from soil
- on surface of plant roots
- mitochondria provide energy from respiration for active transport of mineral ions into root hair cell
- large SA so more water can move in
- large permanent vacuole affects seed of movement of water from soil to cell
xylem cells
- specialised to transport water and mineral ions in a plant from roots to shoots
- lignin deposited, causing cells to die
- become hollow and are joined end to end to form continuous tube for water and mineral ions to move through
- lignin deposited in spirals = help cells withstand pressure from the movement of water
phloem cells
- specialised to carry products of photosynthesis to all parts of plant
- cell walls of each form sieve plants, break down = allow movement of substances from cell to cell
- energy cells need to be alive is supplied by mitochondria of the companion cells
animal cell differentiation
- almost all cells differentiate at an early stage then lose its ability
- can make more of the same cell by undergoing mitosis
- red blood cells can’t divide and are replaced by adult stem cells
- mature animals = cell division only happens to repair/replace damaged cells as they undergo little growth
plant cell differentiation
- cells have ability to differentiate throughout its life
- only differentiate when they reach their final position in the plant, but can still re- differentiate when moved to another position
culturing microorganisms
- growing microorganisms in a lab so scientists can study them
- culture medium contains carbs for energy, minerals, proteins and vitamins
two ways to grow microorganisms in a lab
- in nutrient broth solution
-on an agar gel plate
nutrient broth solution
- make suspension of bacteria to be grown
- mix with sterile nutrient broth(culture medium)
- use cotton wool to cover flask, prevents air from contaminating it
- shake regularly to provide oxygen for growing bacteria
agar gel plate
- agar acts as culture medium
- bacteria grown on it forms colonies on the surface
- hot sterilised agar jelly is poured into a sterilised petri dish, which is left to cool and set (heat)
- wire loops (inoculating loops) are dipped in a solution of microorganism and spread over agar evenly
- lid is taped on and plate is incubated for a few days so microorganisms can grow(upside down)
all equipment must be sterilised with a flame
- kills unwanted microorganism
- no sterilisation = contamination, harmless but will compete with desired bacteria for nutrients and space or could be harmful/potentially produce pathogen
petri dish lid = not completely sealed with tape
- sealing stops airborne microorganisms from contaminating the culture.
- all the way around = harmful anaerobic bacteria growing (no oxygen)
petri dish upside down
- prevents condensation from lid landing on agar surface and disrupting growth
culture incubated at 25 degrees
- higher temperatures (37 degrees) can grow harmful bacteria
- lower temps colonies of such bacteria would not grow
binary fission
- when the cell splits in two (including bacteria) if there is a supply of nutrients and suitable temperature
- e coli can take as little as 20 mins to replicate in the right environment
unfavourable conditions = not more division and die
mean division time
average amount of time taken for one bacterial cell to divide
number of bacteria in a population after given the mean division time formula
bacteria at beginning x 2 ^ number of division = bacteria at the end
(find how many divisions there are first using mean division time)
chromosomes
- The nucleus contains genetic material in the form of chromosomes, which contain coils of DNA
- 23 pairs of chromosomes in each cell in the body (inherit one from mum and one from dad)
gene
short section of DNA that codes for a protein and as a result controls a characteristic (each chromosome carries many genes)
sex cells
- aka gametes and have 23 chromosomes in each cell in total
cell cycle
series of steps cell undergoes to divide
mitosis
one step in the cell cycle - stage where cell divides
cell cycle stage 1
INTERPHASE
- cell grows, organelles (e.g ribosomes and mitochondria) grow and increase in number.
- protein synthesis occurs
- DNA replicated (X shape)
- energy stores are increased
cell cycle stage 2
MITOSIS
- chromosomes line up at middle (equator) of cell
- cell fibres pull each chromosome of the ‘X’ to either side of cell (poles)
cell cycle stage 3
CYTOKINESIS
- two identical daughter cells form when the cytoplasm and cell membranes divide
why is cell division under mitosis in multicellular organisms important?
- for growth and development
- to replace damaged cells
- vital for asexual reproduction - only involves 1 organism (replicates its own cells to produce offspring)
stem cells
- undifferentiated cell which can undergo division to produce many more similar cells, some of which will differentiate to have different functions
types of stem cells
- embryonic stem cells
- adult stem cells
- meristems in plants
embryonic stem cells
- form when egg and sperm cell fuse to form a zygote
- can differentiate into any type of cell
- scientists can clone through culturing and direct them to differentiate into almost ant cell
- could potentially be used to replace insulin-producing cells in those suffering from diabetes
- or new neural cells for diseases like Alzheimer’s
- nerve cells for paralysed with spinal cord injuries
adult stem cells
- found in bone marrow
- can form into many types of cells e.g blood cells
meristems
- found in root and shoot tips
- can differentiate into any type of plant, throughout its life
- can be used for cloning (parent plant may have a certain desirable feature e.g disease resistance, can be used for research or save a rare plant from extinction)
- crop plants with special features can be cloned to produce large numbers of identical plants for farmers
therapeutic cloning
- embryo produced with the same genes as the patient
- embryo could be harvested to produce embryonic stem cells
- can be grown into any cells the patient needs e.g new tissues/organs
- advantage - not rejected (would have the exact same genetic make-up as individual
benefits of research with stem cells
- can replace damaged/diseased body parts
- unwanted embryos from fertility clinics can be used (otherwise discarded)
- more research into process of differentiation
problems of research with stem cells
- we do not completely understand the process of differentiation = hard to control stem cells to form cells we desire
- removal of stem cells result in destruction of the embryo
- religious or ethical objection = seen as interference with natural process of reproduction
- growing stem cells contaminated with virus = infection transferred to individual
- money and time could be better spent into other areas of medicine
- human embryos shouldn’t be used = each is a potential human life
- in some countries are banned
diffusion definition
the spreading out of particles of any substance in solution, or particles of a gas, resulting in a net movement from an area of higher concentration to an area of lower concentration
diffusion characteristics
- many particles close together = collide with each other more often= them moving around and mixing with other particles in the area
- passive (no energy required)
- substances can move over cell membrane via diffusion (in and out of cells) - partially permeable membrane
- molecules have to be small to move
- oxygen, glucose, amino acids and water can cross
- starch and proteins cannot cross
diffusion examples
GAS EXCHANGE in lungs
- oxygen moves through membranes of alveoli into rbc, carried to cells across body for respiration
- carbon dioxide moves from rbc to lungs to be exhaled
EXCRETION
- urea moves from liver cells into the blood plasma
- then transported to kidney for excretion
factors that affect rate of diffusion
CONCENTRATION GRADIENT
- greater the difference = faster rate of diffusion
- more particles are randomly moving down the gradient than moving against
TEMPERATURE
- greater temp = greater movement of particles
- more collisions = faster rate of diffusion
SA OF MEMBRANE
- greater SA = more space for particles to move through = faster rate of diffusion
SA to volume ratio
-size of surface area of the organism compared to its volume
- written in smallest whole numbers
single-celled organisms (SA:V)
- can use diffusion to transport molecules into their body from the air as they have a relatively large SA:V
- due to their low metabolic demands, diffusion across the surface of organism is sufficient enough to meet its needs
multicellular organism (SA:V)
- small so they can’t just rely on diffusion alone
- surfaces and organ systems have a number of adaptations which allow molecules to be transported in and out of cells
M-C organisms adaptations examples to increase effectiveness of an exchange surface
LUNGS
- oxygen to blood and carbon dioxide to lungs
- takes place across surface of alveoli, which are covered in tiny capillaries which supply blood
SMALL INTESTINES
-cells have villi
- digested food absorbed over membrane, into bloodstream
GILLS
- gas exchange in fish
- water passes through mouth and over gills
- gills have gill filaments and upon these are gill lamellae, where diffusion of oxygen into blood and diffusion of carbon dioxide into water take place
- blood flows in one direction, water flows in other
ROOTS
- adapted to take up water and mineral ions
- root hair cells = large SA
LEAVES
- carbon dioxide through stomata for photosynthesis
- oxygen and water vapour move out through them
adaptations in mc organisms
- large surface area = more particles can move through = faster rate of diffusion
- thin membrane = short diffusion pathway = process faster
- efficient blood supply/ventilation = creates steep concentration gradient = faster diffusion
osmosis
- movement of water from less concentrated solution to a more concentrated one through a partially permeable membrane
- passive
dilute solution of sugar
high concentration of water (high water potential)
concentrated solution of sugar
low concentration of water (low water potential)
isotonic solution
- concentration of sugar in external solution = internal
- no movement
hypertonic solution
- concentration of sugar in external solution > internal
- water moves out
hypotonic solution
- concentration of sugar in external solution < internal
- water moves in
osmosis in animals
- external solution is more dilute = moves into animal cells causing them to burst
- external solution is more concentrated = excess water will leave the cell causing it to shrivel
osmosis in plants
- external solution more dilute = water will move into the cell and into vacuole causing it to swell, results in pressure called turgor, essential in keeping leaves and stems of plants rigid
- external solution less dilute = water will move out of cell and will become soft = cell membrane will move away from cell wall (called plasmolysis) and it will die
active transport
- movement of particles from an area where they are in lower concentration to an area where they are in higher concentration
- not passive, requires energy from respiration
active transport in root hairs
- take up water and mineral ions from soil
- mineral ions usually in higher concentrations in cells = diffusion can’t take place
- requires energy from respiration to work
active transport in gut
- substances such as glucose and amino acids from food move from gut to bloodstream
- sometimes lower conc of sugar molecules in the gut than in blood = diffusion can’t take place
- active transport required to move sugar to blood against its conc gradient
