Cell Biology Flashcards
What are eukaryotic cells like and where are they found?
- Are complex (include all animal and plant cells)
- Organism made up of eukaryotic cells
What are prokaryotic cells like and where are they found?
- Prokaryotic cells are smaller and simpler e.g. Bacteria
- Are single-celled organism
Name 5 features of an animal cell
- Nucleus
- Mitochondria
- Cytoplasm
- Cell membrane
- Ribosomes
What’s the function of nucleus?
Contains genetic material that controls activities of cell
What’s the function of mitochondria?
Where most of the reactions for aerobic respiration take place (respiration transfers energy that the cell needs to work)
What’s the function of cytoplasm?
Where most of the chemical reactions happen - contains enzymes that control these chemical reactions
What is the cytoplasm?
Gel-like substance
What’s the function of a cell membrane?
Holds cell together and controls what goes in and out
What’s the function of ribosomes?
Where proteins are made in the cell (where protein synthesis occurs)
What 3 features do plants cells have but not animals cells?
- Cell wall
- Chloroplasts
- Permanent vacuole
What’s the function of chloroplasts?
Where photosynthesis occurs which makes food for plant
What does chloroplasts contain and why?
Contain a green substance called chlorophyll which absorbs light needed for photosynthesis
What is the cell wall made out of (in a plant)?
Made of cellulose
What’s the function of a cell wall?
Supports the cell and strengthens it
What’s the function of a permanent vacuole?
- Contains cell sap (weak solution of sugar and salts)
- Keeps the cell rigid to support plant
What do bacterial cells have instead of nucleus?
Have a single circular strand of DNA that floats freely in
cytoplasm
What are plasmids and where are they found?
Small rings of DNA found in bacterial cells
Do bacterial cells have chloroplasts or mitochondria?
No
What is cell differentiation?
The process by which a cell changes to become specialised for its job
Explain briefly how cells differentiate
As cell change, they develop different subcellular structures = turn into different types of cells
When does most cell differentiation occur?
Occurs as an organism develops
When do animals cells lose the ability to differentiate?
Most animal cells lose the ability to differentiate at an early stage, after they become specialised
Do plant cells lose the ability of differentiate?
Lots of plant cells don’t ever lose the ability
What are cells that differentiate in mature animals used for mainly?
Mainly used for repairing and replacing cells (skin, blood cells)
What are sperm cells specialised for?
Specialised for reproduction
What is the function of a sperm cell?
To get male DNA to female DNA
Name 3 ways a sperm cell is specialised for its job
- Lot of mitochondria to provide energy needed (via respiration)
- Long tail and streamlined head to help it swim to egg
- Carries enzymes in head to digest through egg cell membrane
What are nerve cells specialised for?
Rapid signalling
What is the function of a nerve cell?
To carry electrical signals from one part of body to another
Name 2 ways a nerve cell is specialised for its job
- Are long (to cover more distance)
- Have branched connections at their ends to connect to other nerve cells to form a network throughout body
What are muscle cells specialised for?
Contraction
What is function of a muscle cell?
To contact quickly
Name 2 ways a muscle cell is specialised for its job
- Long so they have space to contract
- Contains lots of mitochondria to generate energy needed for contraction
What are root hair cells specialised for?
Absorbing water and minerals
Name a way a root hair cell is specialised for its job
- Grow long ‘hairs’ that stick out into soil = gives the plant a big surface area for absorbing water and mineral ions from soil
Name 3 animal tissues
- Muscular Tissue
- Glandular Tissue
- Epithelial Tissue
What does the muscular tissue do?
Contracts (shortens) to move whatever it’s attached to
What does the glandular tissue do?
Makes and secretes chemicals like enzymes and hormones
What does the epithelial tissue do?
Covers whole surface of body and some parts of body
In the stomach, describe what the 3 main tissues do
- Muscular tissue moves the stomach wall to churn food
- Glandular tissue makes digestive juices to digest food
- Epithelial tissue covers the outside and inside of stomach
Name the four main tissues in plants
- Epidermal Tissue
- Palisade Mesophyll Tissue
- Spongy Mesophyll Tissue
- Xylem and Phloem
What does the epidermal tissue do?
Covers whole plant
What are epidermal tissues covered in and why?
Covered in waxy cuticle, helps reduce water loss by evaporation
Name a feature (and its purpose) of the upper epidermal tissue
Is transparent so light can pass through to palisade layer
Name a feature (and its purpose) of the lower epidermal tissue
Full of holes (stomata) to increase gas exchange (carbon dioxide diffuse in and oxygen diffuse out)
What does the palisade mesophyll tissue contain?
Lots of chloroplasts
What happens in the palisade mesophyll tissue?
Where most of photosynthesis happens
Name a feature (and its purpose) of the palisade mesophyll tissue
Near top of leaf so it can get most light
Name a feature (and its purposes) of the spongy mesophyll tissue
Big air spaces to allow carbon dioxide to diffuse through leaf (gases to diffuse in and out of cells) & increase surface area
What does the tissues xylem and phloem do?
Help support structure
What are the xylem and phloem?
Network of vascular bundles which deliver water and other nutrients to entire leaf & take away glucose produced by photosynthesis
Define diffusion
Diffusion is the spreading out of particles from an area of higher concentration to an area of lower concentration
How can you increase the rate of diffusion (name 2 way)?
- Bigger the concentration of gradient (different in concentration) = faster the diffusion rate
- Higher temperature = faster rate of diffusion because particles have more energy to move around faster
Define osmosis
Osmosis is the diffusion of water from a dilute to a more concentrated solution through a partially permeable membrane
What is a partially permeable membrane?
Membrane with very small holes in it
What does partially permeable membrane let through?
Only allows tiny molecules (like water) can pass through them and bigger molecules (sucrose) can’t
What does it mean if a solution is isotonic?
Solute concentration of solution is SAME as solute concentration inside cell
What does it mean if a solution is hypertonic?
Solute concentration of solution is HIGHER than solute concentration inside cell
What does it mean if a solution is hypotonic?
Solute concentration of solution is LOWER than solute concentration inside cell
What is active transport?
When substances are absorbed against a concentration gradient (low to high). This requires the use of energy from respiration.
What does active transport allow plants to?
Active transport allows plant to absorb minerals form a very dilute solution, against a concentration gradient (but NEEDS ENERGY from respiration)
Explain how active transport stops us from starving?
- SOMETIMES there’s a lower concentration of nutrients in gut than in blood
- Active transport is used to allow nutrients to be taken into the blood - despite the fact concentration gradient is the wrong way
Name and explain 4 ways that exchange surfaces are adapted to maximise effectiveness (i.e. ways they speed up diffusion)
- Thin membrane - short distance to diffuse
- Large surface area - lots of a substance can diffuse at once
- Efficient blood supply (lots of blood vessels) (in animals) - maintains the concentration gradient
- Gas exchange surfaces often ventilated (animals) - supplies more O2 and keeps concentration difference high
What are villi and where are they found?
Tiny little projections (millions of them) that cover the inside small intestine
How does villi help absorption in the small intestine?
They increase surface area so digested food is absorbed much more quickly into the blood
What 2 features do villi that speeds up diffusion (excluding large surface area)?
- Very good blood supply to assist quick absorption
- Have single layer of surface cells
Name 5 adaptations of alveoli
- Good blood supply
- Very thin walls (lining only one cell thick)
- Ventilation (breathing) - steep concentration gradient
- Moist lining for dissolving gases
- Are folded = massive surface area
Explain how the shape of leaf makes it a good exchange surface
Flattened shape of leaf increases surface area of exchange surface = more effective
Explain how the underneath of a leaf is a good exchange surface
Covered in stomata = carbon dioxide diffuse in & oxygen and water vapour diffuse out
What is the size of stomata controlled by?
Guard cells
What do guard cells do (to help with gas exchange)?
Close the stomata if plant is losing water faster than it is being replaced by roots
What would happen if a plant didn’t have guard cells?
Without guard cells, plant would wilt
Explain how the walls of cells inside leaf forms another exchange surface
Air spaces inside leaf increase the area of this surface so there’s more chance for carbon dioxide to get into cells
What are phloem and xylem cells specialised for?
Specialised for transporting substances
What feature do phloem and xylem cells have that makes them suited for their job?
Xylem cells are hollow in centre and phloem have very few subcellular structures - so stuff can flow through them
What do phloem and xylem cells form?
Form phloem and xylem tubes which transport substances (food, water) around plant
What are stem cells?
Undifferentiated cells that can become `any type of cell
What can we do with stem cells?
Can be grown in labs to produce clones & made to differentiate into specialised cells - to use in medicine or
research
Where are stem cells found mostly?
Early human embryos & umbilical cord of newborn babies
Where are stem cells found in adults?
Liver and bone marrow
Why aren’t stem cells found adults as useful as embryonic stem cells?
But they can’t turn into any type of cell - only certain ones
e.g. blood cells
How can we use adult stem cells to cure diseases (in medicine)?
Stem cells can be transferred from bone marrow of healthy person can replace faulty blood cells
What can we use embryonic stem cells for?
They be used to replace faulty cells in sick people e.g. nerve cells for spinal injuries
What is therapeutic cloning?
When an is embryo made to have same genetic info as a patient
What is the benefit of therapeutic cloning?
Stem cells produced have same genes so they wouldn’t be rejected
Name 3 arguments against stem cell research
- Human embryos have potential human life
- Scientist should concentrate on finding and developing other sources of stem cells
- People can be helped without embryos
Name 2 arguments for stem cell research
- Curing patients who already exist & are suffering = more important than rights of embryos
- Embryos used are unwanted ones from fertility clinics - if weren’t used for research, would be destroyed
Where are stem cells found in plants?
Found in meristems (where growth occurs in plants) = in most parts of the plant
What are stem cells used for (plant wise)?
Used to produce clones of whole plants quickly and cheaply
What can stem cells be used for grow (plant wise - give two ideas)?
- Crops of identical plants - have desired features for farmers e.g. disease resistance
- More plants of rare species (prevent extinction)
What happens when you put a plant cell in a hypotonic solution?
Makes plant stiff - it becomes turgid (normal)
What happens when you put a plant cell in a isotonic solution?
It will become flaccid - it’ll wilt (become floppy)
What happens when you put a plant cell in a hypertonic solution?
It will become plasmolysed (causes irreversible damage)
What happens when you put a red blood cell in a hypotonic solution and why?
It will become lysed - bursts because it doesn’t have a cell wall
What happens when you put a red blood cell in a isotonic solution?
It’ll be normal - nothing
What happens when you put a red blood cell in a hypertonic solution?
It will be shrivelled
Marram grass have rolled leaves and live in dry and hot conditions, explain how this helps them to survive
Water is trapped inside = no concentration gradient
Why don’t single celled organisms require complex structures for gas exchange? Two reasons
- Large SA to Volume Ratio
- Short Diffusion Distance
Why doesn’t algae require complex structures for gas exchange? One reason
Flow of water maintains concentration gradient
What increases a leaf’s surface area to volume ratio?
Flattened shape and internal air spaces
Name one feature of a yeast cell
Has vacuole
What is meant by plasmolysed?
Cell membrane moves away from cell wall
