A2.2: Cell Structure Flashcards
What are the characteristics of living things?
Metabolism
Reproduction
Homeostasis
Growth
Response to stimuli
Excretion
Nutrition
What is metabolism?
The enzyme catalyzed reaction occurring in a cell, including cell respiration
-> Sum of all chemical reactions in a cell
What is reproduction?
The production of offspring (can be asexual or sexual)
-> allows life to create more life
Sexual reproduction:
Two parents and the fusion of haploid sex cells one from each parent
Asexual production:
Involves 1 parent
What is homeostasis?
The ability to maintain and regulate internal conditions within tolerable limits (ex: temp)
-> all living things have mechanisms that keep their internal environment with a certain range despite changes in external environment
What is growth?
The permanent increase in size/mass
-> development is the transformation of the organs
What is response to stimuli?
Also known as sensitivity:
Ability to respond to external or internal changes in the environment and thus improving chances of survival
What is excretion?
The disposal of metabolic waste products, including CO2 from respiration
Humans -> usually through lungs and kidneys
Plant -> usually via leaves, roots and stem
Unicellular -> cell membrane
What is nutrition?
Gaining energy and nutrients for growth and development either by absorbing organic matter or by synthesizing organic molecules
Autotrophs -> use external energy to synthesize carbon compounds from simple inorganic substances
Heterotrophs -> use carbon compounds obtained from other organisms to synthesize the carbon compounds that they require
Explain how a paramecium carries out all of the life processes
(Use image in notes for reference)
Metabolism - cytoplasm
- most metabolic pathways occur in the cytoplasm
Reproduction - macro and micro nucleus
- nucleus can divide to support cell division via mitosis (asexual)
Homeostasis - contractile vacuole
- fills with water (excess from cytoplasm) and expels though the plasma membrane
- manage water content
Growth - food vacuoles/nutrients
- after consuming/assimilating biomass from food -> get larger until it divides
Response - cilia
- wave action of cilia -> moves cell in response to changes in environment
Excretion - anal pore
- plasma membrane controls entry+exit of substances
- includes expulsion of metabolic waste through anal pore
Nutrition - oral groove and food vacuole
- oral groove: guides food particles into the cell
- food vacuoles: contain organism the cell has consumed -> forms at the end of of oral groove
Explain how chlamydomonas carries out all process of life
(Use image in notes for reference)
Metabolism - cytoplasm, mitochondria, chloroplast
- cytoplasm: contains dissolved enzymes that catalyze metabolic reactions
- mitochondria; cellular respiration
- chloroplast: photosynthesis
Reproduction - nucleus
- divides via mitosis (asexual)
- can fuse+divide to carry out a form of sexual reproduction
Homeostasis - contractile vacuole, plasma membrane
- excess water collected then expelled through cell membrane opening
Growth - nucleus, mitochondria, Golgi apparatus
- nucleus: produces protein
- golgi: synthesize protein -> function state
- mitochondria: provides energy (ATP) for growth
Response to stimuli- flagellum; eye spot
- flagellum: allows movement towards light
- eye stoplasma detect light
Excretion - plasma membrane
- oxygen from photo -> diffuses out
Nutrition - chloroplast, pyrenoid
- autotroph -> large single chloroplast to facilitate photosynthesis
- pyrenoid -> concentrate CO2 for increased rate of photosynthesis
What structures do all eukaryotic cells have in common?
Nucleus
Free and bound 80s ribosomes
RER+SER
Golgi apparatus
Vesicle
Lysosome
Mitochondria
Cytoskeleton
Differences in eukaryotic cell structure
Plastids (double membrane organelles which are responsible for manufacture and storing of food):
Animal: x
Fungi: x
Plant: chloroplast (photosynthesis) and amyloplast (store starch)
Cell wall (external to plasma membrane provides strength and protection + turgor pressure):
X
Composed of chitin + other molecules
Composed of cellulose
Vacuoles (membrane bound organelle, stores/removes water/waste products):
Small and temporary
Large and permanent
Large and permanent
Centrioles (paired cylindrical organelles, 9 x 3 microtubules with radial symmetry):
Used to arrange mitosis spindles during cell division and anchor for cilia and flagella
X (only present in those that have swimming male gamete)
Present in male gametes of moss+fern, absent in conifers and flowering plants
Cilia and flagella (extension of cell surface and help in movement and made of centrioles):
present in many animal cells
X (present in some that have swimming male gamete)
Present in male gamete of moss+fern, absent in conifers and flowering plants
What are examples of eukaryotic cells with atypical structures?
Striated muscle fibers/skeletal muscle fibers
Aseptate fungal hyphae
Red blood cells
Phloem sieve tube elements
What are the atypical features of striated muscle fibers/skeletal muscle fibers
Longer (up to 300mm in length compared to cardiac muscle cell (100-150 micrometers))
Multiple nuclei surrounded by a single membrane (sarcolemma)
- on edge rather than center
-> allows faster transcription of protein and increase muscle repair/contraction
Formed from multiple cells fused together (reason why many nuclei) that work together as single unit
Challenges the concept that cells work independently of each other even in multicellular organisms
What are the atypical features of aseptate fungal hyphae
Hyphae: long thread-like filaments or tubes in fungi
- essential in penetration of food sources, production of digestive enzymes, absorption of release nutrients after digestion
- form mycelium (tangled mess of hyphae)
Coenocytic/aseptate hyphae:
Fungal filaments devoid of septa -> No cross wall (form cellular compartments of fungi)
- rapid nutrient distribution due to rapid cytoplasmic streaming
Nuclei -> multinucleate (several nuclei in one continuous cytoplasmic space)
- from nuclear division followed by no cell division
- metabolic boost/increased metabolism (good because fungus seeks to extract+absorb nutrients form environment)
What are the atypical features of red blood cells
Biconcave disc:
Flexible movement (through tiny capillaires)
increased SA for oxygen diffusion and CO2 removal
Haemoglobin:
protein for oxygen binding
Lack of organelles (mitochondria, ER, Golgi, nucleus):
Maximize oxygen transport/haemoglobin/CO2 removal
Acid-base balance:
Through carbonic anhydrase enzyme -> convert CO2 and water to biocarbonates helping balance pH
What are the atypical features of phloem sieve tube elements
Specialized plant cell
Function: transport/distribution of nutrients
Sieve tube -> thick primary walls (always arranged one above the other)
Phloem parenchyma -> made of parenchyma cells and helps store starch and fat
Phloem fibers -> thick walled, elongate, spindle shaped (dead tissue)
Nucleus of companion cells control activity:
Helps maintain metabolic functions it needs -> will die otherwise
Adjacent to each sieve tube element
No standard organelles:
More open exterior/increased rate of transport
No end cell wall:
Easier transport
What is endosymbiosis?
Where one organism lives with another as the relationship beneficial
Must have been engulfed by endocytosis
How did the nucleus develop?
Prokaryote grows -> developed folds in membrane to maintained SA:V ratio
Infolding pinched off -> internal membrane
Nucleotides region enclosed in internal membrane -> nucleus
What is the endosymbiotic theory?
Theory that chloroplast and mitochondria were once free-living prokaryotes that were engulfed by a larger prokaryote and survived to evolve into the modern organelles we know today
Single common unicellular ancestor for all eukaryotic cells
How do scientist think the common eukaryotic unicellular ancestor evolved into heterotrophic cells?
Heterotrophs -> cannot prepare their own food and depend upon autotrophs for nutrition
To overcome small SA:V ratio-> ancestral prokaryotes develop folds in membrane
Infoldings -> organelles like nucleus and RER formed
Larger anaerobically respiring cells engulf smaller aerobically respiring prokaryote (not digested)
-> larger cell gain advantage (ready supply of ATP) and gradually cell evolves into heterotrophic eukaryotes with mitochondria
How do scientist think the common eukaryotic unicellular ancestor evolved into autotrophic cells?
Autotrophs -> organisms that prepare their own food through the process of photosynthesis
Some stage -> heterotrophic cell engulf smaller photosynthetic prokaryote
Cell gain advantage -> alternative source of energy: carbohydrates
Over time -> photosynthetic prokaryote -> chloroplast -> heterotrophs becomes autotrophic eukaryotic
How did the mitochondria develop?
Aerobic bacterium enters larger anaerobic prokaryote (maybe prey or parasite)
Survives digestion -> valuable endosymbiont (cell which lives in se another cell with mutual benefit)
Aerobic bacterium -> rich source of ATP -> allows cell to out-compete other anaerobic prokaryotes
Host cell grows and divides -> so does aerobic bacterium
-> next generation automatically have aerobic bacterium
Aerobic bacterium evolves and assimilates -> mitochondria
(Chloroplast development would’ve been very similar except the benefit would’ve been cell would use glucose/Starch instead of ATP)
What evidence is there supporting the endosymbiotic theory?
Double membrane (one original, one from engulfing)
-> inner membrane has proteins similar to prokaryotic cell membrane
Own DNA (naked and circular)
Ribosomes similar to that in prokaryotes (70s)
Roughly same size as bacteria
Susceptible to antibiotic chloramphenicol
Transcribe their DNA and use RNA to synthesize some of their own protein
Can only be produced by division of pre-existing mitochondria/chloroplast
What are stem cells?
Stem cells are cells that are able to specialize to become different cell types by differentially turning off and on certain genes
What is a genome?
All the genetic information of an organism
Organisms of the same species share most of their genome
All cells within an organism share the same genome
What is differentiation?
The development of specialized structures and functions in a cell
Occurs when different cell types express different genes
Can result in differing shapes and presence (or lack thereof) organelles
What is gene expression?
The process by which the info encoded by a gene is turned into a function
Genes that aren’t housekeeping genes (code for protein that are associated with basic cellular functions) -> differently expressed in different cell types
Regulated by proteins that bind to specific DNA base sequences
What are the basic step of protein synthesis?
DNA -> transcription (in the nucleus) -> RNA -> translation (RER/Ribosomes) -> folding (Golgi apparatus) -> protein
How can environmental conditions change gene expression?
Gene expression can be influenced by the external world and internal world
-> external: location or where it develops
Ex: Siamese cats
-> internal: hormones and metabolism
Hormones are molecules that are produced in one cellular location in an organism -> effects another tissues or cell type
What are tissues (in a biology context)?
A group of cells that have differentiated in the same way to preform the same function
What are the benefits of cell specialization?
Focus on fewer tasks at once -> increased efficiency/energy conservation
Specialized structures and metabolism
Only do one-few things at a time -> faster evolution
What are multicellular organisms?
Composed of more than one cell
Specialized cells of the same type come together to form tissue
In multicellular -> cells lose ability to live independently
Exist in:
All animals
All plants
Most but not all fungi and algae
What are some examples of multicellular organisms?
Epithelial cell -> epithelial tissue -> stomach -> digestive system
Muscle cells -> muscle tissue -> bladder -> urinary system
Neurons (nerve cells) -> nerve tissue -> brain -> central nervous system
Rod and cone cells -> retina -> eyes -> visual system
What are the benefits of multicellularity?
Multicellularity help cells coordinate and communicate with each other
Helps them thrive in most environments
Allows for organisms to grow and for cell specialization
Being part of a cluster -> survival benefit
- less susceptible to predation
What are the two basic steps of multicellular evolution?
- Formation of cellular clusters from single cells
- Differentiation of the cells within the cluster for specialized functions
(Can go back and forth between the two based on what is more beneficial/practical)
What are the two hypotheses for how cell clusters may have formed?
Groups of independents cells come together
Unicellular organism divides, but daughter cell fails to separate -> group of identical cells
P____ and c____
Paramecium
Chlamydonas
