B1 - Cell Structure & Transport Flashcards
What is a eukaryotic cell?
- a plant or animal cell with cell membrane, cytoplasm
- genetic material enclosed in nucleus
- organelles
What is a prokaryotic cell?
- genetic material is not enclosed in nucleus
- no organelles
- DNA found as a loop
- one or more plasmids
- cytoplasm surrounded by cell wall
What is the difference between the two?
- genetic material
- prokaryotic is smaller
What is a plasmid?
- a small ring of DNA
What parts does an animal cell have?
- nucleus, cell membrane, cytoplasm, mitochondria and ribosomes
What parts does a plant cell have?
- nucleus, cell membrane, cytoplasm, mitochondria, ribosomes
- chloroplasts, cell wall and vacuole
Function of the nucleus?
control the cell
Function of the cytoplasm?
site of chemical reactions, has enzymes
Function of the cell membrane?
controls what enters and leaves the cell
Function of the mitochondria?
site of respiration - energy for survival and function
Function of ribosomes?
site of protein synthesis
Function of chloroplasts?
site of photosynthesis, make glucose
Function of permanent vacuole?
supports the cell and contains cell sap
How is the cell wall strengthened?
cellulose
Prefixes for centi, milli, micro and nano?
Centi – 10-2
Milli – 10-3
Micro – 10-6
Nano – 10-9
How is a sperm cell adapted for its function?
- streamlined shape
- tail to swim to ovum
- nucleus has 1 set of chromosomes
- lots of mitochondria from respiration to release energy
- to carry father’s genetic information + fertilise the egg
How is a red blood cell adapted for its function?
- no nucleus so more room for oxygen
- haemoglobin binds to oxygen molecules
- flat biconcave shape to increase surface area
- to transport oxygen around the body
How is a nerve cell adapted for its function?
- Long axon – move impulses in the body
- Dendrites – contact other nerves at synapses
- Mitochondria – energy to make neurotransmitters
- Myelin sheath – provides insulation
- to carry electrical impulses around the body
How is a muscle cell adapted for its function?
- ## to contract and relax to allow movement
How is a root hair cell adapted for its function?
- increased surface area for more water
- permanent vacuole - increased speed of osmosis
- mitochondria - energy for active transport of minerals
- to absorb water and mineral ions from soil
How is a xylem cell adapted for its function?
- few cell structures - they are dead for more space
- supported by lignin
- no nucleus, cytoplasm so water + minerals can flow easily
- to transport water around the plant
How is a phloem cell adapted for its function?
- few cell structures
- supported by companion cells - contain mitochondria for energy transfer and moving food through phloem
- to transport sugars around the plant
What is cell differentiation? (2)
- the process by which unspecialised cells develop/change into their mature forms
- it acquires different sub-cellular structures to enable it to carry out a certain function
Examples of specialised cells?
- stem cells
When do animal cells differentiate?
-Most types of animal cell differentiate at an early stage.
When do plant cells differentiate?
- Many types of plant cells retain the ability to differentiate throughout life.
What are the advantages of using an electron microscope?
- higher resolution and magnification
- can be used to examine a cell in finer detail and has led to a better understanding of sub-cellular structures
REQUIRED PRACTICAL 1:
How do you prepare a slide?
1) add a drop of water to the microscope slide
2) place a thin layer of tissue on slide
3) stain tissue with drops of iodine solution
4) place coverslip on top
REQUIRED PRACTICAL 1:
How do you observe a slide?
1) place slide on stage and use lowest power objective lens
2) turn course focus wheel to bring image into focus
3) increase the power of objective lens to increase magnification
4) turn fine focus wheel to bring the image into clearer focus
What is the formula for magnification?
Magnification=image size/actual size
(IAM)
What is magnification?
size of an image compared to its actual size
What is resolution?
The ability to tell the difference between two points
What is binary fission?
- Asexual cell division used by prokaryotic cells to reproduce and split into two
- As often as once every 20 minutes if they have enough nutrients and a suitable temperature.
What happens during binary fission?
- Plasmids and DNA are copied
- Cell gets bigger and DNA strands move to opposite sides of the cell
- Cytoplasm of each cell splits & new cell walls form
- Daughter cells are formed
- For some bacteria, this occurs every 20 minutes
What conditions do bacteria need for binary fission?
- warm environment
- lots of nutrients
What is the formula for calculating the number of bacteria in a given time?
2^n
n=number of rounds of division in the time given in minutes
eg. bacteria divides every 20 mins. Calculate the number of bacteria present after 3 hours.
3 hours = 180 minutes
180/20 = 9 rounds of division
2^9 = 512 bacteria present
ANSWER NEEDS TO BE IN STANDARD FORM:
512 = 5.12 x 10^2
REQUIRED PRACTICAL 2:
How do you make an agar plate and what is it used for?
1) Agar jellies are prepared in petri dishes to form plates
2) Microorganisms are spread on the plates
3) Keep the plates at below 25C0 - minimise the risk of harmful pathogens growing
REQUIRED PRACTICAL 2:
investigating disinfectants + antibiotics
1) sterilise agar and Petri dish before use, disinfect the bench
2) pass inoculating loop through flame of bunsen burner
3) remove lid of the Petri dish and bottle containing bacteria
4) use inoculating loop to remove bacteria from the bottle
5) spread bacteria over agar and replace lid as quick as possible
6) put lid on the petri dish and secure lid with tape, incubate at 25 degrees for 24 hours
REQUIRED PRACTICAL 2:
what measurement do you need to take to calculate the clear area of no bacterial growth?
the radius of the clear area
REQUIRED PRACTICAL 2:
How would you sterilise equipment before use?
heat over 100 degrees
REQUIRED PRACTICAL 2:
What precautions can you use to avoid contamination?
sterilise, work near a flame, pass inoculating loop through flame, minimise opening of containers
REQUIRED PRACTICAL 2:
Why should the petri dish be stored upside down?
prevent condensation falling on agar plate and disrupting growth of microbes
REQUIRED PRACTICAL 2:
Why should a control disk be used when testing different chemicals?
comparison to compare effect of not using a chemical at all
What is diffusion?
- Spreading out of particles net movement from high to low concentration
What factors affect the rate of diffusion?
- concentration - increased concentration gradient=increased rate
- temperature - increased temp=increased rate(more kinetic energy)
- surface area - increased=increased rate
How does surface area:volume ratio affect the rate of diffusion?
When the cell increases in size, the volume increases faster than the surface area, because volume is cubed where surface area is squared.
How is the small intestine adapted for diffusion?
- long, has villi for large surface area, cell membranes are thing for short diffusion pathway, rich blood supply for steep concentration gradient
How are the lungs adapted for diffusion?
- lots of alveoli for large surface area
- thin membrane for short diffusion pathway
- good ventilation
- good blood supply for steep concentration gradient
How are gills in a fish adapted for exchange?
- large surface area
- thin membrane for short diffusion pathway
- good ventilation + blood supply
What happens during diffusion in a fish?
- oxygen from water into blood in the gill filaments
- carbon dioxide from gill filaments into water
What happens during diffusion in plants?
- CO2 for photosynthesis comes into leaves through stomata
- O2 during photosynthesis comes out of leaves through stomata
What is osmosis?
- diffusion of water from dilute solution to concentrated solution through a partially permeable membrane
REQUIRED PRACTICAL 3:
effects of osmosis on plant tissue
1) cut tubes of potato using a cork borer
2) trim potato cylinder so it is at a controlled length
3) record the mass of the potato cylinder
4) put cylinder in a boiling tube of solution and leave for a fixed period of time
5) remove the cylinder and blot dry
6) record the mass of the potato cylinder
7) measure and record new length
8) repeat twice to calculate average
9) repeat for other concentrations
10) calculate percentage change in mass
How do you calculate percentage change in mass?
calculate percentage change:
change in value/original value x 100
REQUIRED PRACTICAL 3:
When would a potato piece left in solution increase In mass?
Solution would be more dilute than potato so water enters through osmosis
REQUIRED PRACTICAL 3:
When would a potato piece left in solution decrease in mass?
Solution would be more concentrated than potato so water leaves potato through osmosis
What is active transport?
- movement of particles from a dilute solution to a more concentrated solution
- low to high (against concentration gradient)
- energy used from respiration
Example of active transport in animals?
- Sugar to be transferred from a low concentration in the gut to a higher concentration in the blood
- Glucose from the gut to be absorbed, used for respiration
Example of active transport in root hair cell?
- Root hair cells transport ions like magnesium into the plant from soil
- concentration of ions in the soil is lower than in the root hair cell, so active transport is used
- ions are moved into the xylem to be transported to the leaves
