Cells and Processes Flashcards
What is the function of a nucleus in a plant or animal cell?
Contains genetic material that controls activities of the cell
What is the function of a cytoplasm in a plant or animal cell?
A substance where most of the chemical reactions take place in the cell. Enzymes control these reactions
What is the function of a cell membrane in a plant or animal cell?
Holds cell together and controls what goes in and out of the cell
What is the function of a mitochondria in a plant or animal cell?
Where most of the reactions for respiration take place
What is the function of ribosomes in a plant or animal cell?
Where the proteins are made in the cell
What else do plant cells contain which animals do not have?
Rigid cell wall, permanent vacuole and chloroplasts
What is the role of a rigid cell wall in a plant cell and what is it made out of?
Cellulose. Supports and strengthens cell
What does a permanent vacuole contain in a plant cell?
Cell sap –> weak solution of sugar and salts
What is the role of chloroplasts in a plant cell and what are they made out of?
Chlorophyll. Absorb the light energy during photosynthesis
What type of organism is a yeast organism and what is it made out of?
Microorganism. Made up of a nucleus, cell wall, cell membrane and cytoplasm
What type of organism is a bacteria and what is it made out of?
Microorganism. Contains a cytoplasm, cell membrane surrounded by a cell wall
If a bacteria cell doesn’t have a nucleus, what happens to their genetic material instead?
Floats around in the cytoplasm. Some of the genes are found in plasmids
How are palisade cells adapted for photosynthesis?
- Packed with chloroplasts. More are crammed in top
- High SA to absorb more CO2
- Thin shape –> have lots in a leaf
How are guard cells adapted to open and close pores?
- Special kidney shape
- Thin outer walls and thick inner walls
- Sensitive to light –> close at night
- More stomata on underside of leaf
What happens to guard cells when they have too much water?
Go plump and turgid –> Makes cell open and allow gas exchange
What happens to guard cells when they have too little water?
Become flaccid –> Makes cell close which reduces amount of water vapour lost
How are RBC adapted to carry oxygen?
- High SA for absorption
- Packed with haemoglobin
- No nucleus –> allows more haemoglobin
What is the main function of an egg cell?
Carry female DNA and nourish developing embryo –> Contains a lot of food reserves
What happens when a sperm fuses with an egg cell?
Membrane instantly changes -> stops more sperm getting in. Allows for right amount of DNA for offspring
What is the main function of a sperm cell?
Carry male DNA to female DNA. Has long tail and streamlined head. Lots of mitochondria for energy
What are large multicellular organisms made up of?
Organ Systems
What is the process called which cells become specialised?
Differentiation
When does the differentiation of cells take place?
The development of a multicellular organism
What do specialised cells form? (3 stages)
Tissues –> organ –> organ systems
What is the role of a large multicellular organism?
Exchanging and transporting materials
What are similar cells organised into?
Tissues
What is the function of a muscular tissue?
Contracts –> Moves whatever is attached to it
What is the function of a glandular tissue?
Makes and secretes chemicals
What is the function of epithelial tissue?
Covers some parts of the body
What is the role of the glands?
Produces digestive juices
What is the role of the liver?
Produces bile
What is the role of the SI
Absorbs soluble food molecules
What is the role of the LI?
Absorbs water from undigested food leaving faeces
Are plant cells organised into tissues and organs?
Yes
What is the role of epidermal tissue in a plant?
Covers the whole plant
What is the role of the palisade mesophyll tissue in a plant?
Part of the leaf where most of the photosynthesis happens
What is the role of the spongy mesophyll tissue in a plant?
In leaf and contains big air spaces. Allows gases to diffuse in and out of cells
What is the role of the xylem and phloem in a plant?
They transport water, mineral ions and sucrose around the plant
Name the internal structure of the leaf from top to bottom
Waxy cuticle -> epidermal tissue -> palisade mesophyll tissue -> spongy mesophyll tissue (with xylem and phloem in the row) -> epidermal tissue (with stomata and guard cell)
In the root cross section, where is the xylem and why?
Goes through the centre to add strength as the root pushes through the soil
In the stem cross section, where is the xylem and phloem and why?
Xylem forms scaffolding to prevent bending. Phloem is on the outside of cell
Do particles diffuse from a low to high or high to low concentration gradient?
High to low
Define diffusion
Spreading out of particles from an area of high concentration to an area of low concentration
Does diffusion happen in solutions or gases
Both
What happens to the diffusion rate if there is a higher difference in concentration?
Faster diffusion rate
What size molecules can diffuse through a cell membrane and name an example
Small, oxygen, glucose, amino acids
Can particles diffuse both ways?
Yes
Define osomis
The movement of water molecules across a partially permeable membrane from a high to low concentration
Can water molecules pass both ways in the concentration gradient?
Yes
What do you call an area of high water concentration?
Dilute solution
If the water concentration in the tissue fluid is higher than the cell fluid, what is the tissue fluid called and which way does water move?
Hypotic solution, water moves into the cell
If the water concentration in the tissue fluid is lower than the cell fluid, what is the tissue fluid called and which way does water move?
Hypertonic solution, water moves out of the cell
If the water concentration in the tissue fluid is the same as the cell fluid, what is the tissue fluid called and which way does water move?
Isotonic solution, there is no net movement of water
What happens to the plant cells when they are well watered?
Become turgid. Contents of cell push against inelastic cell wall
What is the purpose of turgor pressure?
Helps support plant tissues
What happens to the plant cells when they are not well watered?
Become flaccid -> Lose turgor pressure and plant starts to wilt
What happens to the plants cells if there is a drought and what is this called?
Cytoplasm shrinks, membrane pills away from cell wall. Knows as plasmolysis
What is one way you can investigate diffusion?
Using agar jelly
Name 2 ways which you can investigate osmosis experiments
Using potato cylinders and visking tubing
What are root hairs specialised in?
Absorbing water and minerals
How do root hairs help the plant?
Give a large SA for absorption
How do root hairs take in minerals?
Active transport
What concentration gradient does active transport need to work?
Low to high
Does active transport require energy?
Yes
Name an example where active transport is used in the blood
Low concentration of nutrients in the gut, high concentration of nutrients in the blood
Do smaller organisms have a higher or lower SA:V ratio compared to larger organisms?
Higher
Why is diffusion quicker in single celled organisms compared to multicellular organisms?
- Substances travel a shorter distance
- Have a large SA:V ratio
Why is diffusion across outer membranes in more complex organisms too slow?
- Substances have to travel a longer distance
- Lower SA:V ratio
What do multicellular organisms use instead of diffusion?
Specialised exchange organs -> have specialised exchange surfaces
How are exchange surfaces adapted to be more effective?
- Thin -> Short distance to travel
- Large SA
- Lots of blood vessels
- Gas exchange surfaces are ventilated
Where does gas exchange take place in the lungs?
In the millions of alveoli
How are the alveoli specialised to maximise diffusion?
- V high surface area
- Moist lining for dissolving gases
- Very thin walls and good blood supply
How do villi help the SI?
- Large SA with single layer of surface cells
- Very good blood supply -> Quick absorption
What are contained in chromosomes?
Genes -> Control development of characteristics
What are different versions of the same gene called?
Alleles
Define mitosis
When a cell reproduces itself by splitting to form 2 identical offspring
Mitosis: What happens to the cell at first when it gets the signal to divide?
Duplicates DNA
Mitosis: What happens to the duplicated DNA in the cell?
Lines up at the centre (horizontal) and then pulls apart
Mitosis: What happens after the cell has divided?
Membranes form around sets of chromosomes -> Become nuclei
Mitosis: What is the final stage after the cells have divided and now have a cell membrane around them?
Cytoplasm divded giving 2 identical copies of each cell
What are gametes?
Sex cells
Are gametes diploid or haploid?
Haploid
Define meiosis
Produces cells which have half the normal number of chromosomes (haploid)
Meiosis: What happens at first when the cell gets the signal to divide?
Duplicates DNA
Meiosis: What happens to the DNA after the first division?
Chromosome pairs line up in the centre (vertical)
Meiosis: What happens after the DNA is lined up at the centre?
The pairs are pulled apart
Meiosis: What happens after the first division?
The chromosomes line up again at the centre (vertically) and are pulled apart again -> 4 gametes with a single set of chromosomes in
What happens after 2 gametes fuse?
New cell divides repeatedly by mitosis to form many cells.
What happens to the cells after they divide by mitosis in sexual reproduction?
Cells differentiate forming different kinds of specialised cells
Define differentiation
Process by which a cell changes to become specialised for its job
What are undifferentiated cells called?
Stem cells
What are good about stem cells in terms of medicine?
Can have the potential to cure many diseases
Where can stem cells be found in adults?
Bone marrow
Why are some people against stem cell research?
- Embryos are potential human life
What causes cancer?
Body cells dividing out of control
What is a benign tumour?
- Tumour grows until there is no more room
- Cells stay where they are
- Not normally dangerous
What is a malignant tumour?
- Tumour grows and can spread into bloodstream to other parts of body -> Forms more tumours
- Dangerous
What chemicals can cause cancer?
Carcinogens e.g tobacco smoke. Chemicals interfere with normal cell functions making them divide uncontrollably
What ionising radiation can cause cancer?
UV light and X-Rays
How does ionising radiation cause cancer?
- Breaks down molecules into ions -> Interfere with normal cell functions, cell divides abnormally producing a tumour
