Cell Biology Flashcards
Types of cell
- prokaryotic
- eukaryotic
Prokaryotic cells
- single celled organism
- smaller than eukaryotic
- doesn’t contain membrane bound subcellular structures
Eukaryotic cells
- organism made up of eukaryotic cells
- bigger than prokaryotic
- contains membrane bound subcellular structures
Animal cell type
Eukaryotic
Plant cell type
Eukaryotic
Bacteria cell type
Prokaryotic
Animal cell subcellular structures
- nucleus
- cytoplasm
- cell membrane
- mitochondria
- ribosomes
Nucleus
- contains cell DNA
- controls cell activity
Cytoplasm
- where most chemical reactions take place
- contains enzymes to control reaction
Cell membrane
Controls substances going in and out of the cell
Mitochondria
Where energy is released through aerobic respiration
Ribosomes
Where proteins are synthesised
Plant cell subcellular structures
- nucleus
- cytoplasm
- cell membrane
- mitochondria
- ribosomes
- cell wall
- permanent vacuole
- chloroplasts
Cell wall
- supports and strengthens cell
- made of cellulose
Permanent vacuole
Contains cell sap - weak solution of salt and sugars
Chloroplasts
- where photosynthesis occurs
- contain chlorophyll which absorbs light for photosynthesis
Bacteria subcellular structures
- cytoplasm
- cell membrane
- cell wall
- ribosomes
- plasmids
- strand of DNA floating in cytoplasm
Plasmids
Small rings of DNA
How do light microscopes work
Use light and lenses to form image of specimen and magnify it
What can be viewed with light microscope
- individual cells
- large subcellular structures
How do electron microscopes work
Use electrons to form an image
What can be viewed with electron microscope
- internal structure of mitochondria and chloroplasts
- smaller things like ribosomes and plasmids
Microscope with higher resolution
Electron
Microscope with higher magnification
Electron
Magnification triangle
- AIM
- A - actual size
- I - image size
- M - magnification
Microscopy practical - prepare slide
- add water droplet to slide
- cut onion and use tweezers to peel epidermal tissue
- place tissue on water on slide
- add iodine to stain and highlight cell
- place cover slip on top by standing it upright beside slide, slowly tilt and lower on, avoid air bubbles
Microscopy practical - viewing
- clip slide to stage
- select lowest power objective lens
- use coarse focus knob to move stage up just below objective lens
- look down eyepiece, move stage down till in focus
- adjust fine focus knob to get clearer image
- use higher powered objective lens and refocus for greater magnification
Microscopy practical - drawing
- draw with sharp pencil
- use at least half space available
- draw clear, unbroken lines
- no colouring/shading
- draw subcellular structures in proportion
- write title and magnification
- label features with straight, uncrossed lines
Differentiation
Process by which a cell changes to become specialised for its job
When can animal cells differentiate
At an early stage
When can plant cells differentiate
All through their lives
What are most cells differentiated in mature animals used for
- repair
- replacing cells
Stem cells
Undifferentiated cells that can become specialised
Specialised animal cells
- sperm
- nerve
- muscle
Sperm cell function
Fertilise an egg cell to form an embryo
Sperm cell adaptations
- tail to aid movement
- many mitochondria to release energy for movement
- acrosome head released enzymes to digest egg membrane
- haploid nucleus contains genetic material for fertilisation
Nerve cell function
Carry electrical signals from one part of the body to another
Nerve cell adaptations
- long to cover large distances of the body quickly
- branched connections connect nerve cells together
- fatty myelin sheath to increase speed of messages travelling
Muscle cells function
Contract and relax to make bones move and joints bend
Muscle cells adaptations
- long so they have space to contract
- lots of mitochondria to generate release energy for contraction
Specialised plant cells
- root hair
- xylem
- phloem
Root hair cells function
- absorb water and minerals from soil
- hold plants in place as they grow
Root hair cell adaptations
Tiny hairs increase surface area for more absorption
Xylem cells function
Transport water from roots to other parts of the plant
Xylem cells adaptations
- die and ends break down to form hollow tubes for transportation
- thick cell walls support plant and hold it up for photosynthesis and reproduction
Phloem cells function
Transport sugary water from leaves to rest of plant
Phloem cells adaptations
- few subcellular structures so more stuff can flow through
- next to companion cells with release energy for phloem
Where are chromosomes found
Nucleus
Chromosomes
Coiled up lengths of DNA molecules
Where are genes found
Chromosomes
Genes
Control development of different characteristics
How many copies of each chromosome in the body
2
How many chromosomes in a human cell
23 pairs
Why is cell cycle needed
- growth
- development
- repair
Stages of cell cycle
- growth and DNA replication
- mitosis
Cell cycle - growth and DNA replication
- DNA is spread out
- cell grows
- organelles copy
- DNA duplicates to form X shaped chromosomes (each arm is a copy)
Cell cycle - mitosis
- chromosomes line up
- cell fibres pull chromosomes arms to opposite ends of cell
- membranes form around chromosomes forming 2 nuclei
- cytoplasm and cell membrane divide
- 2 genetically identical daughter cells have been produced
What is mitosis
Division of nucleus
Differentiation
Cell changing to become specialised for its job
Stem cells
Undifferentiated cells that can differentiate into different types of cell based on what instructions they’re given
Types of human stem cell
- embryonic
- adult
Where are human stem cells found
- embryos
- bone marrow
Embryo
Resulting ball of cells formed after an egg cell is fertilised by a sperm cell
Embryonic stem cells
- found in early human embryos
- can turn into any type of cell
Where are adult stem cells found
Bone marrow
Bone marrow stem cells
- found in adults
- can only turn into certain types of cell, like blood
Uses of stem cells
- medicine
- research
How are stem cells clones produced
Grown in a lab
Therapeutic cloning
Stem cells being made to have the same genetic information as a patient so they have the same genes and won’t be rejected by the body
Risks of using stem cells in medicine
Stem cells grown in a lab may become contaminated with a virus which is passed on to the patient, making them sicker
Arguments against stem cell research
- human embryos shouldn’t be used for experiments as they are potential human life
- scientists should concentrate on finding and developing other sources of stem cells so people can be helped without using embryos
Arguments for stem cell research
- curing suffering patients is more important than rights of embryos
- embryos used for research are usually unwanted in fertility clinic so would be destroyed anyway
Plant tissue culture
Collection of techniques used to maintain or grow plant cells, tissues, or organs under sterile conditions
Advantages of plant tissue culture
- plants can be cloned quickly
- plants can be cloned economically
Nutrient culture medium
Solid, liquid, or semi-solid designed to support the growth of a population of microorganisms or cells
Where are stem cells found in plants
Meristem
Where are meristems in plants
Tips of plant roots and shoots
What types of plant cell can meristem tissue differentiate into
Any
Uses of plant stem cells
- produce clones of a plant quickly and cheaply
- used to grow more plants of a rare species to stop them being wiped out
- grow crops of identical plants with desired features, like disease resistance
Diffusion
The net movement of particles from an area of higher concentration to an area of lower concentration
In what substances does diffusion occur
- solutions
- gases
Why does diffusion occur in solutions and gases
The particles are free to move around randomly
What increases rate of diffusion
- larger concentration gradient
- higher temperature
- larger surface area
What can diffuse through cell membranes
Small molecules like oxygen, glucose, amino acids, water
What can’t diffuse through cell membranes
Big molecules like starch and proteins
Osmosis
The net movement of water molecules from through a partially permeable membrane from an area of higher water concentration to an area of lower water concentration
Partially permeable membrane
A membrane with very small holes in it so small molecules and pass through and big molecules can’t
Osmosis practical
- cut potato into identical cylinders and measure mass
- place them into sugar solutions of different concentrations including pure water for 24 hours
- take them out, dry with paper towel, measure mass again
- calculate percentage change in mass
- if water moved in by osmosis, mass with have increased
Active transport
The net movement of particles from an area of lower to higher concentration, requiring energy
Active transport
The movement of particles from an area of lower to higher concentration, requiring energy
What do plants need mineral ions for
Healthy growth
How do root hair cells absorb mineral ions
Active transport
Why do root hair cells use active transport to absorb mineral ions
The concentration of minerals is usually higher in the root hair cell than in the soil
How are nutrients absorbed from the gut to the blood
Usually active transport
Larger organism’s SA:V
Smaller
How are exchange surfaces adapted
- thin membrane - shorter diffusion distance
- large surface area - lots of substances can diffuse at once
- animal exchange surfaces have lots of blood vessels - gets stuff in an out of blood quickly
- animal gas exchange surfaces are well ventilated - gets air in and out
Job of lungs
Transfer oxygen to blood and remove waste carbon dioxide from it
Alveoli
Little air sacs where gas exchange takes place in the lungs
Alveoli specialisations
- large surface area (75m² in humans)
- moist lining for dissolving gases
- very thin walls
- good blood supply
Villi function
Increase surface area in small intestine so digested food can be absorbed into blood faster
Villi adaptations
- single layer of surface cells
- good blood supply for quick absorbtion
How does carbon dioxide get into leaves
- diffuses through stomata
- diffuses into air spaces
- diffuses into cells where photosynthesis happens
Where is the exchange surface on a leaf
Underneath
Where are stomata on a leaf
Underneath
How does oxygen leave the leaf
Diffuses through the stomata
What controls the size of the stomata
Guard cells
When do stomata close
If a plant is losing water faster than it’s being replaced by the roots
What would happen to a plant without guard cells
Wilting
Why does leaf have a flattened shape
Increase area of exchange surface so it’s more effective
What do cell walls inside leaf do
Form another exchange surface
Purpose of air space in leaf
Increase surface area of exchange surface formed by cell walls so there’s more chance for carbon dioxide to get into cells
How does water vapour leave the leaf
- evaporates from the cells inside the leaf then diffuses out the stomata as there is more inside the leaf than the air outside
- some leaves via the leaf surface
Exchange surface in fish
Gills
How do fish get oxygen
- water containing oxygen enters through the mouth and passes into gills
- oxygen diffuses from water to blood
- carbon dioxide diffuses from blood to water
What are gills made of
Thin plates of gill filaments
Purpose of gill filaments
Increase surface area for exchange of gases
What are gill filaments covered with
Lamallae
How do lamellae speed up diffusion
- increase surface area
- have lots of blood capillaries
- thin surface layer of cells to minimise diffusion distance
What happens in lamellae
Blood flows through one direction and water flows through the other to maintain a large concentration gradient between them
Where is the concentration of oxygen highest in fish gas exchange
Water so as much oxygen can diffuse into the blood as possible
