Biology Topic 1: Cell Biology

Eukaryotic Cell

Animal Cells that contain DNA enclosed in a nucleus

Prokaryotic Cell

Plant Cells that contain DNA that isn't enclosed by the nucleus

Which is smaller eukaryotic or prokaryotic cells?

Prokaryotic

Cytoplasm

A watery solution where chemical reactions take place (first stage of respiration)

Cell Membrane

A cell structure that controls which substances can enter or leave the cell.

Mitochondria

A cell structure where aerobic respiration takes place

Ribosomes

A cell structure that is site of protein synthesis

Chloroplasts

Contain chlorophyll and are the sites of photosynthesis

Cell Wall

Made from cellulose and helps strengthens the cell

Permanent Vacuole

Filled with cell sap and helps the plant cell keep it shape

Sperm Cells

Fertilises egg cells by joining together with them

Fertilisation

DNA of both the sperm and egg combine

Why do sperm have tails?

Gives them ability to swim and makes the process of fertilisation easier

Why are enzymes important in fertilisation?

Allows the sperm to digest its way through the outer layer of the egg

Nerve Cell

Send electrical impulses around the body

Axon

Carries the electrical impulses

Myelin

Insulates the axon and speeds up the transmission of nerve impulses

Synapses

Found at the end of axons and junctions which allow the impulse to pass from one cell to the other

Dendrites

Increases surface area so that other nerve cells can connect more easily

Muscles Cells

Contains protein fibres to contract and when contracted protein fibres shorten, decreasing the length of the cell

Why are muscles cells packed with mitochondria?

Provides energy for muscle contraction

Root Hair Cell

thin walls and large surface area for maximum absorption of water and minerals from the soil

Xylem Cells

Long tubes found in the stem that carry water and dissolved minerals from the roots to the leaves

Why do xylem cells have thick walls?

Provides support for the plant

Why do xylem cells have no internal structures?

It makes it easier for water and minerals to flow

Phloem Cells

Tubes that carry dissolved sugars up and down the plant

What do the phloem vessel and sieve plates allow?

Allows dissolved sugars to move through the interior

Companion Cells

Contain mitochondria to provide energy to the phloem vessel cell

Stage

Found at the centre of a microscope and is used to place the slide

Clips

Holds the slide in place

Lamp

Provides the light needed to view the specimen

Objective Lenses

Magnification ranges from 4x to 10x to 40x

Eyepiece Lens

Lens that we look through and contains magnification of 10x

Coarse Focussing Knob

Knob you turn to get your slide into view, this moves the stage a lot. It always is the larger of the two knobs on a microscope.

Fine Focussing Knob

the smaller knob on a microscope you use for fine tuning your focus with on a microscope.

Magnification Equation

Image size/actual size

Cons with Light Microscopes

Limited magnification and resolution

Size of the actual object

Image Size/Magnification

What's found in the nucleus?

Chromosomes, made from the molecule DNA

Body Cells

Contain 2 of each chromosome that are paired

How many chromosomes do body cells contain?

23 pair (46)

Gametes

Contain chromosomes but aren't paired

First stage of mitosis

DNA replicates to from 2 copies of each chromosome

Second stage of mitosis

One set of chromosomes are pulled to the end of each cell. The nucleus also divides

Final stage of mitosis

The cytoplasm and cell membrane divide to form two identical cells

What's mitosis essential for?

Growth and development of multicellular organisms, repair of an organism, asexual reproduction

Stem cell

unspecialized cell that can give rise to one or more types of specialized cells

What do stem cells found in bone marrow form during differentiation?

white blood cells, red blood cells and platelets

Leukaemia

Cancer of the bone marrow

Bone marrow transplant step 1

the infected bone marrow is destroyed using radiation

Bone marrow transplant step 2

Patient receives bone marrow from a donor

Bone marrow transplant step 3

Stem cells in donor's bone marrow divides and forms a new bone marrow to differentiated to form red blood cells

Risks of bone marrow transplant

Donor's bone marrow needs to be compatible otherwise the white blood cells produced will attack the patient's body, viruses can be passed from donor to the patient's body

Therapeutic cloning

The production of embryonic stem cells for use in replacing or repairing damaged tissues or organs

What can therapeutic cloning be used to treat?

Diabetes and paralysis

What's the issues with therapeutic cloning?

Some think it's wrong due to the ethical and religious issues it creates

Plant stem cells

Roots and buds contain meristem tissue that differentiate to form plant tissue

Why would cloning plants be useful?

We can stop rare plants from going extinct and produce crops for farmers

Diffusion

net movement of particles from an area of higher concentration to an area of lower concentration

Why are cells surrounded by a high concentration of oxygen?

Transported into the bloodstream via the lungs

Urea

waste product formed in the liver, filtered out of the blood by the kidneys, and excreted in urine

Difference in concentrations

concentration gradient, the greater this is, the faster diffusion takes place

Factors that effect diffusion

The higher the temperature, the greater rate of diffusion. Surface area, the greater it is the greater diffusion rate

surface area to volume ratio

a variable that decreases as cells grow, so that it sets a limit to the size of cells.

How do fish respirate?

Oxygen-rich water passes into the mouth. Then it flows over gills, where oxygen is transported to the bloodstream.

Gills

Covered in fine filaments, where gases passes into and out the blood

Diffusion in fish

Deoxygenated blood passes into the filament. Oxygen diffuses from the water into the blood. Oxygenated blood returns to the body

Filaments

give the gills a massive surface area. have a thin-membrane to provide a short diffusion pathway

What does having an efficient blood supply allow the filaments to do?

Takes oxygenated blood away which ensures a high concentration gradient

Osmosis

diffusion of water from a dilute solution to a concentrated solution through a permeable membrane

Dilute solutions

contain a high concentration of water

Concentrated solutions

contain a low concentration of water

What do partially permeable membranes allow?

Some molecules to pass through but not all molecules

Concentration of cytoplasm

low concentration of water

What will osmosis cause a cell to do in a low concentration?

expand and in some cases even burst

What will osmosis cause a cell to do in a high concentration?

shrink

What will osmosis cause a plant cell to do when placed in water?

expand but not burst due to the cell wall causing it to be turgid or shrink and become flaccid

Practical Osmosis Step 1

peel potato because the skin might affect osmosis

Practical Osmosis Step 2

Use cork borer to produce 3 cylinders of potato because will cause all cylinders to be same diameter

Practical Osmosis Step 3

Use scalpel to cut cylinders to the same length (3cm)

Practical Osmosis Step 4

Use ruler to measure length of each cylinder and a balance to measure mass

Practical Osmosis Step 5

Place each cylinder into test tubes and fill them with 10cm^3 of a 0.5 molar sugar solution to the first test tube

Practical Osmosis Step 6

add 10cm^3 of 0.25 molar sugar solution to the second test tube and 10cm^3 of distilled water to the third

Practical Osmosis Step 7

Leave potato overnight to allow osmosis to take place

Practical Osmosis Step 8

Remove potato cylinders and roll them onto paper towels to remove any surface moisture

Practical Osmosis Step 9

measure length and mass again and write down results in a table

Practical Osmosis Step 10

Calculate % change: change in value/original value x 100

What happens to a potato cylinder in water via osmosis?

The potato cylinder gains mass as water moves into it.

What happens to a potato cylinder in a concentrated sugar solution via osmosis?

The potato cylinder loses mass as water moves out.

What does it mean when the line crosses the x-axis in an osmosis experiment?

There is no change in mass because the concentration outside the cell is the same as the inside.

What does it show when the line cross the x-axis?

the concentration is the approximate concentration inside the cell

Active transport

movement of substances from a more dilute solution to a more concentrated solution (against the concentration gradient), energy from respiration is required.