3 - Cell Structure Flashcards
Cell theory
cells are of universal occurrence and are the basic units of organisms
Eukaryotic
cells with DNA in a membrane-bound nucleus
Prokaryotic
no nucleus
Nucleus; nuclear envelope
double membrane that controls entry and exit of substances, the outer membrane is continuous with ER
Nucleus; nucleoplasm
granular, jelly-like substances that makes up the bulk of the nucleus
Nucleus; pores
allow passage of large molecules (eg. RNA) in and out of the nucleus
Nucleus; nucleolus
manufactures ribosomal RNA and assembles ribosomes
Nucleus; chromosomes
protein-bound, linear DNA
Nucleus; function
control activities of the cell, retain genetic info, manufacture ribosomal RNA and assemble ribosomes
Mitochondria; function
site of AEROBIC respiration, produces energy carrier molecule ATP
Mitochondria; membrane and cristae
outer and folded inner membrane which forms cristae (extensions of inner membrane), cristae provide a large surface area
Mitochondria; matrix
where reactions occur/aerobic respiration occurs, makes up the majority of the mitochondria, contains proteins, lipids, ribosomes, DNA and enzymes
Mitochondria; ATP
energy carrier molecule, cells with high metabolic activity need more ATP so have more mitochondria
Chloroplast; function
site of photosynthesis, contains DNA and ribosomes so it has the ability to make required proteins
Chloroplast; chloroplast envelope
a highly selective double membrane
Chloroplast; thylakoids
disc like structures containing chlorophyll, make up stacks called grana, some have extensions to adjacent grana
Chloroplast; grana
stacks of up to 100 thylakoids, site of light absorption (first stage of photosynthesis)
Chloroplast; stroma
fluid filled matrix containing enzymes and starch grains where the synthesis of sugars occurs (second stage of photosynthesis)
Endoplasmic Reticulum (ER)
continuous with outer membrane of nucleus, encloses network of tubules and cisternae, transport system
ER; cisternae
flattened sacs
Rough ER
ribosomes present on outer surface, provide LSA for synthesis of proteins, provide pathway to transport proteins
Smooth ER
lacks ribosomes on outer surface, synthesises, stores and transports lipids and carbohydrates
Golgi; structure
similar to SER in structure but more compact, stack of membranes make up cisternae, round hollow structures are vesicles
Golgi; functions
add carb. to proteins to form glycoproteins, produce secretory enzymes, secrete carbohydrates, form lysosomes, transport and modify lipids
Golgi; process
modifies proteins by adding non-protein components, ‘labels’ and sorts them, transports them in vesicles which are pinched off the end of the cisternae, vesicles fuse with cell membrane to release contents
Lysosomes; formation
formed when vesicles produced by the Golgi contain enzymes, 50 may be contained in a single lysosome
Lysosomes; function
hydrolyse material ingested by phagocytic cells, digest worn out organelles for reuse, autolysis - break down cells after death, release enzymes to outside or to phagocytic cell
Ribosomes; function
site of protein synthesis
Ribosomes; structure
small cytoplasmic granules, made of 2 sub units; one large and one small, contains ribosomal RNA
Ribosomes; 70S and 80S
70S - found in prokaryotic cells, mitochondria and chloroplast
80S - found in eukaryotic cells and larger
RNA
ribonucleic acid
Cell wall; function
provides mechanical strength against cell bursting due to osmosis, also provides strength to the plant as a whole. Allows water to pass along it - helps with the movement of water along the plant
Cell wall; structure
microfibrils of cellulose embedded in a matrix
Cell wall; middle lamella
thin layer between adjacent cell walls
Vacuole; structure
fluid filled sac bound by a single membrane (tonoplast), contains solutions of mineral salt, sugars, waste, amino acids and sometimes pigment
Vacuole; function
support plants and make them turgid, sugars and amino aids act as a temporary food store, pigment colours petals
Expressing genes
all cells in an organism contain the same genes, they become specialised by only expressing some of the genes in a particular cell, the combination of expressed genes gives the cells a specialized structure and number of organelles
Tissue
group of cells with similar structure and function, that work together to carry out that function
Epithelial tissue
lines surfaces of organs, protective, secretes chemical substances
Ciliated epithelial tissue
has cilia on the surface, hair-like structures that waft mucus (or ovum in the oviducts)
Xylem
consists of several tissue types, transports water and mineral ions through plants, provides mechanical support
Organ
a combination of tissues that are coordinated to carry out several functions (usually one main function)
Stomach tissues
muscle to churn contents, epithelial to protect stomach wall and secrete chemicals and connective to hold other tissues together
Organ system
groups of organs that work together to carry out a bodily process
Object
the matter put under the microscope and studied
Image
appearance of an object when viewed under a microscope
Increasing magnification
this doesn’t increase the resolution of an image, just the size
Magnification
how many times bigger the image is when compared to the object
Magnification =
size of image ÷ size of real object
Isolating organelle
this is necessary in order to study the structure and function of them
Cell fractionation
the process where cells are broken up and separated into their organelles
Cell fractionation; cold, buffered solution with the same water potential as the tissue
cold to reduce enzyme activity that might break down the organelles, same water potential to prevent organelles from bursting shrinking due to osmotic gain/loss, buffered so that the pH doesn’t fluctuate
Homogenation
cells are broken up by a homogeniser (blender) to separate the organelles from the cell in a resultant fluid known as the homogenate, this is filtered to remove large cells or pieces of debris
Ultracentrifugation
fragments in the filtered homogenate are separated in a centrifuge, the homogenate is spun at very high speeds to create a centrifugal force
Supernatant
the fluid left at the top after the sediment has fallen to the bottom in the centrifuge
Total magnification =
magnification of eyepiece × magnification of objective lens
Light microscopes and resolving limit
wavelength cannot get through as the structures get smaller, if the gap is smaller than200nm the wavelength is too long to pass through, they have a resolving limit of 200nm
Transmission EM
electron beam passes through/past a thin section of specimen, parts of the specimen absorb electrons so appear dark and parts allow it to pass through so appear light
Scanning EM
the beam is directed onto the surface of the specimen, where the electrons scatter , the scattering pattern can be used to build up a 3D image
Palisade cell; function
to carry out photosynthesis
Palisade cell; adaptation
contains large amounts of chlorophyll, large number of chloroplasts, have a long shape to maximize light absorption
RBC; function
to carry oxygen from the lungs to respiring tissue
RBC; adaptation
don’t have a nucleus in order to maximize space for haemoglobin, biconcave shape to increase SA and increase rate of diffusion of oxygen
Ciliated cell; function
to move the ovum along the oviduct (fallopian tube)
Ciliated cell; adaptation
tiny hair-like structure (cilia) waft the ovum
Nerve cell; function
rapid conduction of messages through the body
Nerve cell; adaptation
long nerve fibres to carry impulses long distances, dendrites extend to other neurons to make connections
Root hair cell; function
to absorb water and nutrients from the soil
Root hair cell; adaptation
long narrow protrusion to increase SA and rate of diffusion, lots of mitochondria to release energy for active transport, large vacuole for storage
Sperm cell; function
to fertilise ovum/egg cells
Sperm cell; adaptation
tail allows it to swim to the ovum, many mitochondria release energy for this mobility, enzyme in head allows it to digest wall of the ovum to fertilise it
Muscle cell; function
to contract and relax to allow the movement of muscles
Muscle cell; adaptation
elongated and elastic features allow them to contract/relax, many mitochondria to release energy for contraction
Prokaryotes; DNA
not in a membrane bound nucleus and not associated with proteins
Prokaryotes; organelles
no membrane bound organelles
Bacteria; size
range from 0.1 to 10 micrometres in length
Bacteria; cell wall
all have a cell wall consisting of murein (a polymer of polysaccharides and peptides), physical barrier that excludes certain substances and protects against mechanical damage and osmotic lysis
Bacteria; capsule
many have a capsule of mucilaginous slime, protects against other cells and helps groups of bacteria to stick together for further protection
Bacteria; pili
hair-like structures that allow them to attach to other bacterial cells
Bacteria; other structures
they have a cell surface membrane, cytoplasm, 70S ribosomes, glycogen granules and oil droplets, genetic material in a circular strand of DNA and plasmids
Bacteria; use of glycogen granules and oil droplets
food reserves
Plasmids; vectors
commonly used as vectors - carriers of genetic information in genetic engineering
Plasmids; structure
small circular strands of DNA
Plasmids; function
possess genes that may aid the survival of bacteria in adverse conditions eg. produce enzymes that break down antibiotics, can reproduce themselves independently
Bacteria; flagella
whip-like protrusion used for movement, may have more than one
Viruses
acellular, non-living particles
Viruses; size
20-300nm
Viruses; genetic material
contain nucleic acids such as DNA and RNA in capsid (protein coat), can only multiply in host cells
Viruses; lipid envelope
has attachment proteins which are vital in allowing the virus to identify and attach to a host cell
Bacteriophage
a virus that uses a bacterial cell as a host, nuclear material is injected into bacterial cell which is trapped by tail fibres
Prokaryotes; mitochondria
do not have mitochondria and have a mesosome instead as site of respiration
Prokaryotes; mesosome
folded section of inner membrane that provides a large surface area for respiration, prokaryotes are able to produce ATP
Reasons cells divide
for growth, repair and replacement, and reproduction
Mitosis
produces 2 genetically identical cells, occurs in all somatic (body) cells, parent cell divides once
Interphase
prior to mitosis the cell is actively synthesising proteins, chromosomes are invisible and DNA replicates
Prophase
chromosomes become visible, centrioles develop spindle fibres (animal cells), nucleolus disappears and nuclear envelope disintegrates
Metaphase
chromosomes line up along the equator and spindles attach to the centromeres
Anaphase
centromeres divide in two, spindles pull individual chromatids apart and towards poles whilst mitochondria gather round the spindle to provide energy
Telophase
chromosomes become longer and thinner forming chromatin, nucleolus and nuclear envelope reform and cytoplasm divides by cytokinesis
Cell division in prokaryotes
occurs by binary fission
Process of binary fission
Circular DNA molecule replicates and both attach to cell membrane, plasmids replicate, cell membrane begins to grow between the DNA and pinches inwards dividing the cytoplasm in two, a new cell wall forms between the DNA molecules dividing the original cell into to two identical daughter cells
Replication of viruses
cannot undergo cell division, attach to a host cells with the attachment proteins on their surface, inject their nucleic acid into the host cell which instructs the host cells organelles to produce the viral components which are then assembled into viruses
Cell cycle; G1
cells increase in size, produce RNA, synthesise proteins, everything prepared for DNA synthesis (10 hours)
Cell cycle; S
DNA replication takes place (9 hours)
Cell cycle; G2
cell continues to grow and make new proteins, other organelles replicate for mitosis (4 hours)
Cell cycle; M
mitosis occurs (1 hours)
Cell cycle; interphase
consists of phases G1, S and G2, occupies most of the cell cycle, sometimes called the resting phase as no division occurs
Cell cycle; nuclear division
where the nucleus divides either into two (mitosis) or four (meiosis)
Cell cycle; cytokinesis
process by which the cytoplasm divides to produce 2 or 4 new cells
Length of the cell cycle
length varies between organisms, typically about 24 hours for a mammal of which 90% is interphase
Cancer
a group of around 200 diseases caused by a growth disorder in cells
Cancer; cause
the result of gene damage to the genes that regulate mitosis and the cell cycle, this leads to uncontrollable growth and division of cells, which forms an abnormal group of cells called a tumour
Tumours; common locations
lungs, prostate gland (male), breasts and ovaries (female), large intestine, stomach, oesophagus, and pancreas
Tumours; becoming cancerous
tumours become cancerous when they change from benign to malignant
Malignant tumours
grow rapidly, less compact, more likely to be life threatening
Benign tumours
grow more slowly, more compact, less likely to be lifer threatening
Cancer treatment
often involves killing dividing cells by blocking a part of the cell cycle, hence ceasing cell division and cancer growth
Chemotherapy
drugs used to treat cancer, usually disrupt the cell cycle by preventing DNA from replicating, inhibiting the metaphase stage of mitosis by interfering with spindle formation
Problems with chemotherapy
also disrupt the cell cycle of normal cells, although some drugs are more effective against rapidly dividing cells, cancer cells have a particularly fast rate of division so are damaged to a greater extent than normal cells
Hair loss in cancer patients
hair producing cells are affected by chemotherapy because hair cells rapidly divide
