GCSE Biology (Topic 1: Cell Biology)

Eukaryotes vs Prokaryotes: what do each type have?

- Eukaryotic cells (plant and animal): have a nucleus, membrane-bound organelles

- Prokaryotic cells (bacteria): no nucleus, DNA in a loop, may have plasmids, smaller in size

Tell me in ascending order the prefixes for calculations.

nano -9

micro -6

milli -3

centi -2

base 0

kilo 3

mega 6

giga 9

Animal and plant cells: how many subcellular structures are there? What are they?

Animal cells (5):

nucleus

mitochondria

ribosomes

cell membrane

cytoplasm

Plant cells (+3):

cellulose cell wall

chloroplasts

permanent vacuole with cell sap

What is the function of the nucleus?

controls and regulates the activities of the cell, contains genetic material (DNA)

What is the function of the mitochondria?

cellular respiration, releases energy

What is the function of ribosomes?

location for protein synthesis

What is the function of the cell membrane?

permeable, controls the movement of substances in and out of the cell

What is the function of chloroplasts?

contains the green pigment, chlorophyll, which absorbs light energy for photosynthesis. contains the enzymes needed for photosynthesis.

What is the function of the cell wall?

strengthens the cell and supports the plant

What is the function of the cytoplasm?

Site of chemical reactions, presence of nutrients

What is the function of the vacuole?

keeps the cell turgid

light vs electron microscopes

Electron microscopes use a beam of electrons instead of light rays.

Magnification equation?

magnification = image size/actual size

How is a sperm cell specialised?

- Long tail and streamlined head to swim faster

- Lots of mitochondria to provide energy

How is a nerve cell specialised?

- long and thin

- dendrites for recieving signals

- fatty myelin sheath surrounding them

efficiently transmit electrical impulses

How is a muscle cell specialised?

for contraction

so they have lots of mitochondira

for energy

skeletal, cardiac, smooth

How is a root hair cell specialised?

Lots of mitochondria for active transport (mineral absorption)

Long projection to increase the surface area to absorb

Thin cell walls

How is a xylem cell specialised?

No end walls, forming a continuous, hollow tube.

- Strengthened by lignin.

- Not alive.

Transport in the xylem is one way and does NOT require energy.

Lignified cells = wood.

How is a phloem cell specialised?

made up of living cells

Sieve tubes have no nuclei.

Has a perforated end so its cytoplasm connects one cell to the next.

completely dependent on companion cell

Companion cells provide energy.

Attaching to each sieve tube

What is the meaning of differentiation?

becoming specialised for a function

How do bacteria reproduce?

- Bacteria multiply by simple cell division (binary fission)

- as often as once every 20 minutes if enough nutrients and suitable temperature.

Name 2 ways to culture bacteria.

- nutrient broth solution

- as colonies on an agar gel plate

What happens during mitosis (4 points)?

1) Grow and increase the number of sub-cellular structures such as ribosomes and mitochondria.

2) Replicate DNA. Two of each chromosome.

3) One set of chromosomes is pulled to each end of the cell and the NUCLUES DIVIDES.

4) Cytoplasm and cell membranes divide.

Function of stem cells from human embryos.

cloned and made to differentiate into most different types of human cells.

Function of stem cells from adult bone marrow.

form many but LIMITED types of cells, including blood cells.

Function of stem cells in plants (Meristem tissue).

Can differentiate into any type of plant cell, throughout its life

What TWO conditions can stem cells treat?

diabetes and paralysis

What are THREE issues facing the use of stem cells?

1. Ethics (potential for human life)

2. Immune system may reject cells

3. transmitting virus and tumour development

https://youtu.be/PQPwbPuCPy4?si=skg3TOY535d0DgHn&t=35

Therapeutic cloning

Define diffusion. (4) Give an example of where it occurs.

- The spreading out of the particles of

- any substance in solution, or particles of a gas,

- resulting in a net movement

- from an area of higher concentration to an area of lower concentration

Define osmosis. (3) Give an example of where it occurs.

- The diffusion of water

- from a dilute solution to a concentrated solution

- through a partially permeable membrane

Define active transport. (4) Give an example of where it occurs.

- the movement of substances

- from a more dilute solution to a more concentrated solution

- against a concentration gradient

- using energy from respiration.