GCSE biology paper 1 revision

This was made for the May 2024 AQA GCSE exams paper 1, they may not apply to current exams or other exam boards

Describe the difference between Eukaryotic cells and Prokaryotic cells

Prokaryotic cells store DNA in plasmid loops, they do not have a nucleus

What 5 features are present in all Eukaryotic cells

cell membrane,nucleus,mitochondria,ribosomes and cytoplasm

what is the cell membranes function?

entry + exit control

what is The cytoplasm function?

chemical reactions

What is the ribosomes function?

protein synthesis

What is The mitochondria's function?

Site of aerobic respiration

what is the nucleus's function?

controls cell activities and contains cell DNA (genetic material)

what are the 3 features only present in plant cells

chloroplasts, cell wall, permanent vacuole.

What is the function of the chloroplasts?

absorb light energy for photosynthesis

what is the cell wall?

Strong cellulose to support cell structure

what is the function of the permanent vacuole?

supports cell structure by filling it with Sap.

What cells are Eukaryotic?

Animal and plant cells

What makes a cell Eukaryotic?

They contain a nucleus

What is a prokaryotic cell

A cell without a nucleus

What structures are in a prokaryotic cell?

Cell membrane, cytoplasm, flagellum, plasmid (ring of dna) ribosomes, DNA, bacterial cell wall

What is the purpose of the flagellum?

To aid with cell movement

What are Plasmids

Small loops of DNA with useful genes

what is the purpose of the bacterial cell wall?

For structure and protection

What is the difference between a plant cell wall and a bacterial cell wall?

A bacterial cell wall is not made up of cellulose

Name the differences between eukaryotic and prokaryotic cells without talking about the nucleus

Prokaryotic cells do not contain mitochondria or chloroplasts

Give a short definition for cell specialisation

Cells change their size, shape, and internal structures to carry out specific functions in organisms

How is the root hair cell different to a plant cell found in the leaf

It does not contain ribosomes or chloroplasts as it does not need them

What is the function of the root hair cell

To absorb water and mineral ions from the soil

What is the function of the Xylem and the Phloem?

To transport substances around the plant.

What does the Xylem transport?

Water

What does the Phloem transport?

Sugars and amino acids

What is the function of a sperm cell?

To fertilise an ovum (egg)

How has the sperm cell adapted?

Tail to swim faster and lots of mitochondria to allow it to swim faster.

What is the function of the red blood cell?

Transport oxygen around the body

How has the red blood cell adapted for its function?

No nucleus so it can carry more oxygen, contains haemoglobin (red pigment) that binds to oxygen molecules and is a flat bi-concave disc shape to allow for a higher surface area-to-volume ratio

What is the function of the muscle cell?

To contract and relax to allow movement

How has the muscle cell adapted for its function?

Contains protein fibres, allows it to contract, contains lots of mitochondria to allow for movement

What is the function of the nerve cell?

Carry around electrical impulses through the body

How has the nerve cell adapted?

branched endings (dendrites) to make connections to other neurons or effectors and myelin sheath into insulate the axon to increase transmission speed

What is the function of the Palisade cell?

To enable photosynthesis in the leaf

How has the palisade cell adapted to its function?

It had lots of chloroplasts to absorb light energy and it’s located at the top of the leaf so It can absorb the most light energy

Cell differentiation

Cells become specialised through the process of differentiation, where different genes are turned on and off in each cell to change their shape and sub-cellular structures so they become adapted to carry out a particular function

What are undifferentiated cells?

Stem cells

When can plant cells differentiate?

Plant cells have the ability to differentiate all throughout their life.

When can plant cells differentiate?

Animal cells differentiate at an early stage and once they are specialised, very few can change, cells just divide by mitosis

What is the equation for magnification?

Image side divided by actual size

Electron microscope

Uses a beam of electron to form images, samples cannot be living, expensive, high magnification, high resolution

Light microscope

Uses light to form images, living samples can be viewed, relatively cheap, low magnification, low resolution

Which microscope allows for viewing of sun cellular structures?

Electron microscope

Describe the microscope practical.

Begin by extracting onion cells and place them on a slide, stain with iodine and cover the sample, gently place the slide onto the stage and clip into place, rotate the objective lens to the lowest power first, once focused then increase the magnification of image, to focus the image adjust the course focus wheel and the fine focus wheel as suited

Where are chromosomes found?

Inside the nucleus of a cell

What shape is dna?

Double helix

What are the short sections in DNA?

Genes

How many pairs of chromosomes are found in human cells?

23

Describe the interphase process in the cell cycle

First the cell replicates dna, then it grows (elongates) in sizzle and increases the number of sub-cellular structures, then the mitosis phase begins

Describe the mitosis process of the cell cycle

Mitosis is the actual cell division stage where one cell splits into two identical daughter cells, this starts when chromosomes are pulled apart to opposite sides of the cell and true n the cell membrane and cytoplasm divides

What is the purpose of the cell cycle?

It allows organisms to grow and replace cells in damaged tissues or organs

What are the three types/ sources of stem cells

Embryonic stem cells, adult stem cells (eg from bone marrow) and plant stem cells

What cells can an embryonic stem cell differentiate into?

Nearly any type of animal cell

What can an adult stem cell differentiate into?

Certain cells, eg, bone marrow cells can only differentiate into types of blood cells

What can plant stem cells differentiate into?

Any type of plant cell, can be used to clone plant

What is therapeutic cloning?

can be used to produce embryonic stem cells that are genetically identical to the patient

Define diffusion

The movement of particles from an area of high concentration to an area of low concentration

passive diffusion

does not require energy

What factors affect the rate of diffusion?

reducing the distance particles have to travel, increasing temperature and increasing surface area of membrane

What have exchange surfaces adapted to maximize the rate of diffusion?

thin walls,large surface area and good blood or air supply

how do you work out surface area to volume ratio?

surface area divided by volume

What is osmosis?

The net movement of water molecules from a dilute solution to a more concentrated solution through a semi-permeable membrane

what does the semi-permeable membrane allow through?

small molecules but not large ones

What factors affect rate of osmosis?

temperature, surface area, concentration gradient

water will move into or out cells depending on…

The difference in concentration of the cytoplasm compared to the solution outside the cell

cells in dilute solution…

water moves into cells by osmosis , animal cells swell and can burst, plant cells swell but don't burst due to cell wall.

cells in solution with same concentration as cytoplasm…

no osmosis,cells remain the same, this is why blood plasma is The same concentration as blood as cytoplasm

cells in concentrated solution…

water moves out of the cell by osmosis, animals cells shrink and in plant cells the vacuole shrinks and cytoplasm can pull away from cell wall

describe the practical for osmosis

place potato pieces in different concentrations of salt/Sugar solutions and leave Them later, calculate the percentage change in mass (negative if lost mass, positive if not)

what is the independent variable for the osmosis practical?

concentration in solution

what is the dependent variable for the Osmosis practical?

change in mass of tissue

What is the control variable for the osmosis practical?

anything that can effect the rate of osmosis e.g. volume of solution, length/volume of The tissue pieces, temperature of the solution

what is active transport?

the movement of partials from a low concentration to a high concentration against their concentration gradient using energy.

what factors effect active transport?

number of mitochondria available, oxygen

cell

the smallest living unit and building blocks of life

tissue

A group of similar cells working together to carry out a function

organ

A group of tissues working together to carry out a function

Organ system

groups of organs- multiple organ systems work together for an organism

salivary glands in mouth

secrete saliva that contains the enzyme amylase to digest Carbohydrates

Amylase

digests carbohydrates

stomach

contains hydrochloric acid to kill bacteria and secretes protease enzymes to digest proteins

protease

digests proteins

small intestine

where absorbion of small molecules into the blood occurs. Contains all 3 enzyme types including lipase to digest lipids/fats

lipase

digests lipids/fats

what does Amylase digest starch into

glucose

what does protease digest protein into

Aminoacids

what does lipase digest lipids into?

glycerol + fatty acids

the rate of enzyme action can be effected by. . .

temperature, PH, surface area of substrate

What are amino acids used for?

to build proteins for growth

what is glucose used for?

to build carbohydrates e .g. glycogen as an energy store or in respiration

what are fatty acids used for?

to make lipids as an energy (fat) Store.

What are digestive enzymes

they break down large insoluble molecules to small soluble molecules which can be absorbed through cell membranes into the blood to be transported and used to build new molecules or for respiration.

what is bile produced for?

bile is produced to neutralise stomach acid and helps digest fat

where is bile produced?

the liver

what is bile?

bile is a chemical (not an enzyme) that helps to emulsify large fat droplets into smaller fat droplets to increase the surface area of the lipids so that lipase enzymes can bind and break down the lipids faster

how do we test for starch?

Add iodine, colour change from yellow/ brown to blue/black

how do we test for protein?

Add Biuret reagent, colour change from light blue to purple

how do we test for glucose?

Add benedict's reagent and heat > 80°C colour change from light blue to brick red

how do we test for lipids?

Add ethanol then add water and shake/mix, A cloudy white emulsion forms